Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: tubenit on September 09, 2014, 06:05:35 pm
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Trying to come up with a legible Marshall Major schematic. The original was VERY difficult for me to read some of the values on. And I think how Marshall drew this up complicated reading the schematic.
Once I get this verified and/or corrected, then I plan to post a couple of mods reported to be good with this amp.
IF someone would look over this & offer edits or a thumbs up, I would be appreciative. I am attaching an editable SCH version if someone wants to use that for edits and corrections.
NOTE the atypical phase invertor topology ................ never seen anything quite like that before? Not sure about the values in that areas of the schematic at all?
With respect, Tubenit
EDIT: will repost corrected schematic thanks to Silvergun's edits
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I need some practice with Express SCH so I took a couple minutes and made a couple adjustments based on what I think I see on the original schematic.
These are the changes to look for from your original:
- Changed input fuse value to 10 amp
- Added 2.7K resistor to cathode of V2 in series with 100K (even though I don't understand why it's there)
- Moved junction of .02 coupling cap and 1M resistor feeding grid of V2 pin 7 (moved pin # also)
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Doesn't the 1M go to ground and the coupling cap go to the 2.7K/110K junction on V2? Makes a concertina PI to feed the 2 driver triodes.
Nope, just looked at the schemo.
Brad :think1:
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Doesn't the 1M go to ground and the coupling cap go to the 2.7K/110K junction on V2? Makes a concertina PI to feed the 2 driver triodes
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That sure would make sense to me!
Brad, I am thinking your probably right, but it sure doesn't look that way on the original????? I am puzzled by it. Maybe just a mistake on Marshall's original?
http://el34world.com/charts/Schematics/files/marshall/Marshall_major_1967u_lead_200w.pdf (http://el34world.com/charts/Schematics/files/marshall/Marshall_major_1967u_lead_200w.pdf)
Hey, I just found this ............... Brad, you are right on!!! Good catch!! The 270R in the Major schematic should be 270k also!!
http://www.drtube.com/schematics/marshall/200w.gif (http://www.drtube.com/schematics/marshall/200w.gif)
With respect, Tubenit
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Here's a big snip.... :dontknow:
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I think Brad is correct !!!! This schematic makes more sense to me.
Take a look at this off the DR. Tube site.
http://www.drtube.com/schematics/marshall/200w.gif (http://www.drtube.com/schematics/marshall/200w.gif)
Tubenit
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Hey, I just found this ............... Brad, you are right on!!! Good catch!! The 270R in the Major schematic should be 270k also!!
WOW!
:huh:
They repeated the mistake on this schematic as well:
http://el34world.com/charts/Schematics/files/marshall/Marshall_major_1966_200w_pa.pdf (http://el34world.com/charts/Schematics/files/marshall/Marshall_major_1966_200w_pa.pdf)
And this one:
http://el34world.com/charts/Schematics/files/marshall/Marshall_major_1978u_bass_200w.pdf (http://el34world.com/charts/Schematics/files/marshall/Marshall_major_1978u_bass_200w.pdf)
NICE WORK BRAD!
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I just looked in TUT5 in the Marshall Major chapter (7) and it's drawn like the schemo that tubenit just posted.
It's a bootstrapped concertina PI driving to triodes, 1 for the push side and 1 for the pull side of the KT88's.
Brad :icon_biggrin:
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That PI made no sense to me either, I kept looking at it thinking I was missing something because of the way it was drawn, but it was drawn incorrectly. :BangHead: :cussing:
Brad :laugh:
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CHECK out the great Marshall Major tone ................
OK, I am thinking that cranked tone of the Major with the OWM (one wire mod) and PPIMV (post phase invertor master volume) that is in this video thread: http://el34world.com/Forum/index.php?topic=17530.0 (http://el34world.com/Forum/index.php?topic=17530.0)
................. is probably something pretty similar to one of these schematics.
With respect, Tubenit
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Yes, there needs to be grid leak for the cathodyne. There were several mistakes on the original drawing. It has been so long, I can not remember them all... I do remember the phase inverter issue and one in the power supply - but there were several. Plus, there were undocumented changes over the years that are not reflected in any drawings. I am totally swamped right now, but I will dig out my marked up schemo in a day or two and share. One necessary upgrade is to change the screen resistors from 220 or 250 5 watt (they came with both) up to a 1K 10watt. It will be a heck of a lot more stable. I can recommend a great surface mount if anyone is interested. The original 220/250's were these big doorknob resistors.
Jim
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change the grid resistors from 220 or 250 5 watt (they came with both) up to a 1K 10watt.
I am presuming you mean the screen resistors? Correct?
With respect, Tubenit
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I am totally swamped right now, but I will dig out my marked up schemo in a day or two and share.
:bravo1:
You've got me shopping for KT88s,,,,so it's the least you can do. :evil5:
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change the grid resistors from 220 or 250 5 watt (they came with both) up to a 1K 10watt.
I am presuming you mean the screen resistors? Correct?
With respect, Tubenit
What? what? SG did it! :angel
Uhh, old age alert...
Jim :help:
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SG, No doubt you will have this thing breadboarded by 10:30am tomorrow morning! You amaze me! :worthy1:
Jim
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Hey Sluckey, IF you read this can you confirm that this makes sense to you also, please?
The PI and driver looks good.
There's something missing in the bias winding.
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Hey Sluckey, IF you read this can you confirm that this makes sense to you also, please?
The PI and driver looks good.
There's something missing in the bias winding.
got my attn. too: bias winding...maybe it should be a FWB with the (+) side grounded?
missing connection between 200uF series stack & 56K series stack.
diff-amp grid-leaks should be 270k? i'd use 470K. just because. :p
missing dot on 1M grid-leak of cathodyne and 2.7K Rk and 100K split. schematic shows jump and no conn.
looks exceedingly ice pick-ish likely just before near total hearing loss... unless you play bass, why?
flyback diodes across OT 1/2 primaries would probably help considerably. why not just run pentode mode and pull screen B+ off the floating CT. should be about 325V after more smoothing around 300V...of course, with fly-back diodes as well. you still get 100W/pair plus you don't need as much drive signal.
edited the 1967 model schema - probably more to the tune of what most here would build: a 1959 front-end with the major power amp?
--pete
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Thanks gentlemen! I appreciate the help.
I am not sure what you guys are saying regarding the bias control?? Can you offer a little more explanation about that & I'll correct it in my schematic and repost then?
I am also wondering how close KT66 tubes are to KT88 tubes in tone? Anybody know?
with respect, Tubenit
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This schematic shows the missing center tap for the bias winding...
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EXCELLENT! Thanks for the help, as always!! Will edit the schematics and repost later today (hopefully).
Best regards and respect, Tubenit
Someone offered me this response also (below):
One mod you should do while its open is to buss all the output tubes Cathodes down and run it into a inline fuse as the HT fuse is too slow to respond to a shorted output tube and then the OT goes south!
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Jim,
I'd love your best educated guess on something .............................
Q1: IF you built the Major with only two KT88's (using the one wire mod and PPIMV), what is your best guess on the
percentage of the essence of the original Major tone that you could preserve? (example: like 93% of the essence
or 87% of the essence of the tone, etc......)
Q2: IF you built the Major with only two KT66's and then did cathode biasing, what is your best guess on the percentage
of the essence of the original Major tone that you could preserve? Maybe 75%?? or what ????
I am betting a nickel that it would be a fabulous sounding amp, but it may be far enough away from the original
KT88 Major tone to not be considered still in the ballpark of the Major tonewise?
To add some clarity, what I am asking is playing the Major at home ............... that "playing at home tone" being the standard of reference in this discussion vs. all 200 watts cranked to "11" with ear bleeding, pants flapping, tornadic force of a sunami wall of tone.
:icon_biggrin:
And before you go saying that less than the full force of 200 watts of cranked KT88's is heresy, ....... I do remember that you yourself have built cute little Firefly amps.
:icon_biggrin: :m8
With respect, Tubenit
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Why not take it way on down? Maybe a pair of 6AQ5s? Call it Major Minor. :icon_biggrin:
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Does anyone know the HT and screen voltages that were used on this amp? Do you think there is room for the Sluckey inspired Plexi/800 circuitry with dual tone stacks, active fx that can be switched out of the signal path, the one wire mod and PPIMV? I think two KT88s would be appropriate for this build unless you need more than 490 volts for the KT88s. Would like to know the answer to Tubenit's Q1 in reply 20 above though before a final tube count would be established.
I really liked the tone coming out of that video. I would like to have one of those.
Thanks
Mike
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Why not take it way on down? Maybe a pair of 6AQ5s? Call it Major Minor.
Jim,
Hey, it was Sluckey that said that not me! :l2: :evil5:
I only thought it was a really great idea before he posted it (all the way down to the same name of Major Minor.)
Sometimes great minds think alike!
With respect, Tubenit
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To interject, hopefully without being too much of a distraction,,,I offer this:
- The 'unique' driver stage came into question when I was messing around with the SSS
- Some of the guys were questioning the value of that driver, and if it would be 'needed' if you were only trying to drive 2 output tubes and not 4
- My personal experimentation led me to feel that there was a valuable quality in the 'tone response' that was generated by that stage,,,and that it is worth using for that reason alone.
- IMO, I feel that the combination of that driver stage, pushing KT88s at high voltage into a UL OT is the foundation of the essence of why this amp sounds different than more commonly built marshalls
why not just run pentode mode and pull screen B+ off the floating CT. should be about 325V after more smoothing around 300V...of course, with fly-back diodes as well. you still get 100W/pair plus you don't need as much drive signal.
Will that change the 'character' of the output stage?.....what effect?
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Does anyone know the HT and screen voltages that were used on this amp? ...unless you need more than 490 volts for the KT88s.
A lot higher, based on people that have worked on the amps, the B+ is well over 600V, and depending on the mains voltage perhaps over 700V. No modern tube could survive such abuse without making some adjustments, also part of the sound is also due to the use of an UL OPT. It's quite a different beast compared to the typical Marshall designs.
Here (http://meyer-repair.blogspot.com.es/2011/02/majestic-marshall-major.html) is an interesting article on the Majors.
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Here is an interesting article on the Majors.
That is an interesting article! I'm sort of thinking now that 6AQ5's may not be the most optimal tube for 650 volts?
:icon_biggrin:
Seriously, I am wondering about the idea of a pair of cathode biased KT66, one wire mod and PPIMV? And not using a UL output transformer? I wonder how close that might emulate the Major sound in that YouTube?
With respect, Tubenit
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Does anyone know the HT and screen voltages that were used on this amp? ...unless you need more than 490 volts for the KT88s.
A lot higher, based on people that have worked on the amps, the B+ is well over 600V, and depending on the mains voltage perhaps over 700V. No modern tube could survive such abuse without making some adjustments, also part of the sound is also due to the use of an UL OPT. It's quite a different beast compared to the typical Marshall designs.
Here (http://meyer-repair.blogspot.com.es/2011/02/majestic-marshall-major.html) is an interesting article on the Majors.
jazbo8
Thank you for the reply. I read a few things about the 1967. Seems that Richie Blackmore of Deep Purple fame had the preamp cascaded so the 1967 was Marshall's first master volume amp. Therefore, the Sluckey idea would definitely work.
I am not 100% sure but it sounds like they started to have the problems with the tubes and the output transformers frying when they increased the voltage on the KT88s from the 480 to 620 volt range and overdrive pedals were being added to the signal path. Not sure if that is when they went to the ultralinear OTs or not but would like to know if anyone could enlighten. I would like to know the difference in tone between an amp with say a Plexi OT at 480 volts versus the ultra linear OTs that were used. Guess I need to look up the specs on four KT88s to see what ohm rating they require.
As I recall this is the amp SRV used before the SSS but had to quit using because he couldn't find matching quads of KT88s at the time. He used it for his clean tones. After that the SSS filled that role.
Hope this reply isn't off track. I sure would like an amp that sounds like the one in that video.
Thanks
Mike
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Jeff,
I know you are one to appreciate original thought, so here's one for ya...(not sure how original, and maybe the amp in the demo was done this way??)
'What if' we placed the PPIMV between the phase inverter and driver tube?
So that with distortion added in the preamp, we wouldn't be overloading the grid of those driver triodes...
This comes from some of my experimentation where I was getting an unfavorable sound by adding distortion to the preamp of the SSS
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Hey, it was Sluckey that said that not me!
Should be OK. I play a Strat and know the cords to Lazy! :laugh:
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SRV used them for his clean sound.
Also the tone stack is simi-active because it is in the -FB loop. This is part of this amps sound. But there comes a point when getting close to diming the amp that the -FB loop can't keep up and drops out.
KOC, TUT5, 7-5 , Marshall Major chapter;
"Dialing the EQ up or down introduces an "error" in the transfer function of the amp, which FB tries to correct. At some point it cannot, the loop decouples electrically, and the amp distorts. Before that point, the speaker output has been altered from looking identical to the input, to being something different but still useful."
Brad :icon_biggrin:
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'What if' we placed the PPIMV between the phase inverter and driver tube?
KOC, TUT5, 7-6 , Marshall Major chapter;
"Note that placing the (MV) dual pot between the concertina and the paraphase (driver triodes) stages is no different than the single-section pot at the input of the concertina (in place of the grid leak R). This is because the concertina is not a gain stage and should not be considered as such.
Brad :think1:
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'What if' we placed the PPIMV between the phase inverter and driver tube?
KOC, TUT5, 7-6 , Marshall Major chapter;
"Note that placing the (MV) dual pot between the concertina and the paraphase (driver triodes) stages is no different than the single-section pot at the input of the concertina (in place of the grid leak R). This is because the concertina is not a gain stage and should not be considered as such.
Brad :think1:
Good point......so much for original thought :l2:
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The difference in tone between KT66 and KT88 is Major. :l2:
Speaking of the clean tone only since usually distortion is created in the preamp in Marshall designs, the difference is quite similar to the difference between 6V6 and 6L6 except more pronounced. KT66's produce a very balanced tone from bass to treble and has strong upper mid which is referred to as chime or sparkle the KT88 is the opposite. While it does have a great upper mid the same as the KT66, but the KT88 has such a strong bottom the sparkle is not readily as noticeable.
Running both hard the KT66 would be a framing hammer hitting the chest, whereas the KT88 would be a 2 pound hammer. The difference is readily noticeable since it has much more bass extension.
I wired the OT both ways and UL provides a much more fluid, smooth feel. Problem is it can be rigid feeling according to the transformer. I prefer the Dynaco replacement UL over the one Hammond sells and I have used both. The last one I built I used a a complete set from triode here:
http://triodeelectronics.com/mk3trbuwfrch.html (http://triodeelectronics.com/mk3trbuwfrch.html)
Using this set with KT88 and SS rectification will put loaded plate voltages 560v, but with KT120 it drops to 520's.
I like this best so far. The Hammond 1650R is used weighs 12 lbs and is very stiff and the 1650N will get hot if cranking the amp, but it has a better feel.
I have a jtm45 that originally ran KT66 and I switched it to kt88 because I have quite a few of the tube. The only difference I noticed running at lower voltages is you need to brighten the amp up at lower volume. Tweaking would take care of it as jtm45 can be dark anyway.
A LarMar PPMIV is great as it seems to simply decrease headroom. I use Gold Lion Chinese KT88 and they hold up well and they sound really nice. If you want to keep the power section clean and full and jangley the KT120 work fine, but if you want to get the power tubes distorting (be in another room) the KT88 are by far the best choice as the distorted tone of the KT120 is very harsh, but they will deliver the best clean signal and react very well to pedals and preamp overdrive and an even stronger bottom end. Think killer metal.
All of these experiences are with a driver 12Ax7 and no negative feedback.
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For a master volume control couldn't you just put a 1MA pot between the wiper of the treble control and the input to the PI (the .02 cap)? Hopefully that wasn't mentioned and I just didn't understand that it was mentioned.
Thanks
Mike
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For a master volume control couldn't you just put a 1MA pot between the wiper of the treble control and the input to the PI (the .02 cap)? Hopefully that wasn't mentioned and I just didn't understand that it was mentioned.
It's just another way of saying what Brad posted here from TUT
"Note that placing the (MV) dual pot between the concertina and the paraphase (driver triodes) stages is no different than the single-section pot at the input of the concertina (in place of the grid leak R). This is because the concertina is not a gain stage and should not be considered as such.
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The difference in tone between KT66 and KT88 is Major. :l2:
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All of these experiences are with a driver 12Ax7 and no negative feedback.
Good stuff Ed, all good info....
What made you go with the 12AX7 in the driver spot?.....did you rule out the 12AU7 early and then just stick with it?
I also like what you wrote about the UL OT combined with the KT88....again, I think that's some of the magic that Jimbo is experiencing :dontknow:
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As I am reading this, it sounds like the KT88 perhaps would be the truest tone even with two tubes?
I can not tell if the UL OT is critical from what I am reading. Sounds like it's a factor but not critical? So, I am thinking you can "reasonably" capture the Major sound without the UL OT. Is that correct?
It sounds like the PPIMV is the preferred master volume of the 3 mentioned? Option #1 is the better?
I am not sure what Silvergun was actually suggesting, but I drew up what I thought he might be suggesting? SG, feel free to correct the drawing and repost if I am not understanding you?
What about the idea of a pair of KT88 that is cathode biased with each having their own resistor and electrolytic cap?
I am trying to think of how to get reasonably that tone in the YouTube without 200 watts of power tubes. And instead have it be more like 60-80 watts?
With respect, Tubenit
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Option #3, not between the treble pot wiper and the .022 coupling, replace the 1M grid leak R at pin 7 with a 1MA pot.
If you go with option #1 (PPIMV) you can get the pre to slam the concertina and the paraphase driver triodes, more small bottle distortion.
Brad :icon_biggrin:
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For a master volume control couldn't you just put a 1MA pot between the wiper of the treble control and the input to the PI (the .02 cap)? Hopefully that wasn't mentioned and I just didn't understand that it was mentioned.
It's just another way of saying what Brad posted here from TUT
"Note that placing the (MV) dual pot between the concertina and the paraphase (driver triodes) stages is no different than the single-section pot at the input of the concertina (in place of the grid leak R). This is because the concertina is not a gain stage and should not be considered as such.
No, see reply #38. MV pot between the treble wiper and the .022 coupling cap will effect the tone (thin it out) as you dial the MV down.
"Note that placing the (MV) dual pot between the concertina and the paraphase (driver triodes) stages is no different than the single-section pot at the input of the concertina (in place of the grid leak R). This is because the concertina is not a gain stage and should not be considered as such.
Brad :icon_biggrin:
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I am not sure what Silvergun was actually suggesting, but I drew up what I thought he might be suggesting? SG, feel free to correct the drawing and repost if I am not understanding you?
You got it....that was my suggestion......I was trying to have a good idea :icon_biggrin:
I like your first example - Option #1
I guess that the 12AU7 can take a big input signal due to the bias point/ high plate V,,,so you shouldn't have to worry about my concern about dropping some signal before it gets there. (Brad's terminology of 'slamming' it sounds good to me :icon_biggrin:)
I am trying to think of how to get reasonably that tone in the YouTube without 200 watts of power tubes. And instead have it be more like 60-80 watts?
I'm not sure that that specific tone is 'all that special"....it's definitely very cool, but is mostly based on preamp distortion...
So, I'm thinking that I agree with you that the UL OT shouldn't be the determining factor...(for capturing that demo tone)
IMO, you're getting pretty close with what you're envisioning.
I've got a 4.2k pri K OT here that I can try with 2 KT88s when I can get around to it....560V(ish) plates like Ed mentioned.
I also guess that cathode biasing becomes more of a heat issue at higher power due to increased dissipation, which partially would explain why it is shy'd away from.
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I'm not sure that that specific tone is 'all that special"....it's definitely very cool, but is mostly based on preamp distortion...
So, I'm thinking that I agree with you that the UL OT shouldn't be the determining factor...(for capturing that demo tone)
I wired the OT both ways and UL provides a much more fluid, smooth feel. Problem is it can be rigid feeling according to the transformer. I prefer the Dynaco replacement UL over the one Hammond sells and I have used both.
Brad :think1:
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No, see reply #38. MV pot between the treble wiper and the .022 coupling cap will effect the tone (thin it out) as you dial the MV down.
I understand 100%...
I was trying to simplify it for Mike J and show him that a similar solution was suggested by TUT in your previous post
The 1m pot would 'become' the grid leak R
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The difference in tone between KT66 and KT88 is Major. :l2:
...
All of these experiences are with a driver 12Ax7 and no negative feedback.
Good stuff Ed, all good info....
What made you go with the 12AX7 in the driver spot?.....did you rule out the 12AU7 early and then just stick with it?
I also like what you wrote about the UL OT combined with the KT88....again, I think that's some of the magic that Jimbo is experiencing :dontknow:
SG, I tried a lot of driver tubes and I thought I would prefer an 12Au7 and it is fine for bass. Speaking of power sections only. It seems the preamp and tonestack of this particular amp (apples to oranges) prefers a 12Ax7 You know me, I had to try everything that would fit into socket.
If I were simply trying to get the best clean tone from the PA, then it is a 12At7. The 12Ax7 is clean, clean, clean with the Treble and Bass at high noon. Where the difference is the amp distorts nicely when you add Treble and Bass, but the lower the gain is in the driver tube the less there is. I am to stoopid to know why. :icon_biggrin: That is why I just have to try it because I have never been able to get it to sound good on paper.
I have used a Leslie 147 amp with cathode bias running KT88, but a different amp again. Nothing seems as clear and I got a lot of mushy sounding bottom in comparison. I probably did not do it correctly because the tubes had a shorter life, but then again apples to oranges. The NOS tungsol 6550 is probably a stouter tube than the Chinese Gold Lion KT88 even though the KT88 is rated for higher voltage.
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ED,
Good answer...again, all good stuff... :thumbsup:
The more I get you to say the more info there will be for T to make his decisions :icon_biggrin:
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I'm not sure that that specific tone is 'all that special"....it's definitely very cool, but is mostly based on preamp distortion...
So, I'm thinking that I agree with you that the UL OT shouldn't be the determining factor...(for capturing that demo tone)
I wired the OT both ways and UL provides a much more fluid, smooth feel. Problem is it can be rigid feeling according to the transformer. I prefer the Dynaco replacement UL over the one Hammond sells and I have used both.
Brad :think1:
UL OPT changes the output tubes' characteristics, so it definitely has an influence on the sound, but I agree, in the Youtube clip, it's more about the preamp distortion, since I think that the amp was no where near full power during the recording, so the power tubes distortion was not really that big a factor.
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To interject, hopefully without being too much of a distraction,,,I offer this:
- The 'unique' driver stage came into question when I was messing around with the SSS
- Some of the guys were questioning the value of that driver, and if it would be 'needed' if you were only trying to drive 2 output tubes and not 4
- My personal experimentation led me to feel that there was a valuable quality in the 'tone response' that was generated by that stage,,,and that it is worth using for that reason alone.
- IMO, I feel that the combination of that driver stage, pushing KT88s at high voltage into a UL OT is the foundation of the essence of why this amp sounds different than more commonly built marshalls
why not just run pentode mode and pull screen B+ off the floating CT. should be about 325V after more smoothing around 300V...of course, with fly-back diodes as well. you still get 100W/pair plus you don't need as much drive signal.
Will that change the 'character' of the output stage?.....what effect?
i have no idea how much. probably some. one can only speculate without experimentation. there's only one way to really find out: modify the real thing, unless you can cobble together an exact or near exact copy.
--pete
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Tubenit:
The 270Ω grid leaks for the differential amplifier stage (the one between the split-load inverter and the output tubes) must be a typo in the original schematic. If the "270" in the schematic is correct, then they must be 270kΩ. Otherwise, they'd severely load the split-load's output.
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The 270Ω grid leaks for the differential amplifier stage (the one between the split-load inverter and the output tubes) must be a typo in the original schematic. If the "270" in the schematic is correct, then they must be 270kΩ. Otherwise, they'd severely load the split-load's output.
You forgot to change the drawing.
Brad :icon_biggrin:
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You forgot to change the drawing.
Brad :icon_biggrin:
Who gave this guy coffee today?
:grin:
Thanks for sharing that TUT stuff today sir...very helpful!
Schemo looks great T!
I look forward to a break in my schedule when I can give this some attention.
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:icon_biggrin:
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Ok, edited and corrected. Thanks! Two tube with OWM & PPIMV is what I personally would do.
And also the original with four KT88's.
With respect, Tubenit
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Jeff,
I've played a lot of Marshalls and a few with KT-88's in place of the EL34's. Nothing ever came close. I'm sure your design would sound great, but in my humble opinion, I don't think it would replicate the original design. Ed's description of the kt66 to kt88 was spot on. At the same volume, the kt66 would scream, but the kt88 would kick you first - one of my favorite things! I also think the UL has a LOT to do with the final product. And unlike Ed, every Major I had sounded better with the au7 (see my post on the Soundclip thread), but I was pushing it pretty hard.
There is a lot of misinformation going around about the Major. The cause of all the original Major's issues comes from a VERY crappy Dagnall output tranny. They used masking tape for "insulation" between the windings. If set up properly there is ~620v B+ (always was). The flyback condition produced 1800v spikes. So blam across pins 2-3 or any connection close to a ground. Later models came with double insulation for the high v runs, ceramic tube bases, and no sharp solder joints. Eventually (always...) the Dagnall went poof. Those still under warrantee in the States back then received a custom wound OP tranny from a guy named Otto in New York - a fantastic replacement. Those custom trannies have lived in Ritchie Blackmore's Majors for years. The original design of the Major was penned by the MO Valve company. It is the only amp that Marshall produced that was not designed in house. Marshall had built several "six gun" EL34 models in the wattage race with Hiwatt. They were pushed to the limit and crappy components caused failure after failure. So they called the main manufacturer of the KT88 for help. They essentially gave them a HiFi amp. There were two distinct versions of the Major. The Marshall 200, which was called the Pig and had active tone controls. Other than Mick Ronson, everyone hated it. The Major came next and it came in a Lead, Bass, and PA version. Deep Purple had stacks and stacks of the Major PA to achieve their loudest band in the world designation back in the early 70's. There have been statements that due to parts and tube availability Marshall decided to quit making the Major after only about 300 were made. That is also not true. Warrantee costs were killing them, but were easily absorbed as a flagship loss leader. What really put the Major out to pasture was the factory logistics. In one shift a single woman could assemble 6 - 50watt, 4 - 100watt, or 1 - Major (with help due to the weight). In the early to mid 70's they could not meet demand as it was, so.... Ritchie Blackmore's amp tech used to work for Macintosh. He was the one who figured out what was wrong with the Major's design and helped them find a solution. Many Marshall products were wrung out on the road with Deep Purple in those days.
Any new OP UL tranny will work in this amp. Ed likes the Hammond, many Major owners have gone with the Heyboer replacement and have been really happy with no smoke issues. I think it would be very easy to replicate the original tone without blowing out the windows. Yes, speaker breakup and moving a lot of air contributes - as well as a tinge of KT88 distortion (the best!). But the full body response of the UL KT88's working with this unique preamp is awesome at any volume. You could run those tubes at 350v and have a great 60 watt amp with the OWM and PPIMV. Just because a car will do 150 mph, doesn't mean you have to go that fast. I've only found a few tube brands that work well in my amp. With that plate voltage and screens only .001v behind (with the original screen resistors), they get beat up pretty bad. Lower the B+ and just about anything out there will work. Ed has done a LOT of KT tube swapping with his builds, so I would defer to him on anything new. I'm still stuck on my =C=.
Hope this esplains it and debunks some myths. This is great to see! I have been beating the Major drum for years, it's good to see you guys running with it! :worthy1:
Jim
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Jeff, I meant your OTHER design, not the one you just posted.
Jim
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At the same volume, the kt66 would scream, but the kt88 would kick you first - one of my favorite things! I also think the UL has a LOT to do with the final product. And unlike Ed, every Major I had sounded better with the au7 (see my post on the Soundclip thread), but I was pushing it pretty hard.
How the heck do you have any hearing left??? :w2:
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Ed likes the Hammond, many Major owners have gone with the Heyboer replacement and have been really happy with no smoke issues.
Ed prefers the Dynaco more - "I prefer the Dynaco replacement UL over the one Hammond sells and I have used both."
Slightly OT, why did KOC referred to the differential amplifier as "paraphase", they aren't really the same thing, are they?
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something along the lines of what i'd build.
maybe the following as well:
a) up the values of the coupling and bypass caps on the ice-pick channel.
b) adding cathode fuses for each KT-88.
c) neg bias PS go/no-go mains lockout.
--pete
EDIT: current copies of schema in reply #82.
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Pete, I always value your input and thoughts on stuff like this. THANKS for sharing your schematic. I am posting it in the SCH Library along with the others.
http://el34world.com/Forum/index.php?topic=17556.new#new (http://el34world.com/Forum/index.php?topic=17556.new#new)
Jim, great info about this! You and Ed are a wealth of valuable insight and info on this amp.
I think this is a very interesting thread and discussion & I appreciate everyone's contributions. Cool stuff.
I don't plan on building this amp, but I was very intrigued by the design of it and loved the YouTube tone that Jim posted. My hearing is not very good already. I can not afford to play a really loud amp and lose what I have left. Maybe someday, I'll get a chance to build this for a friend or a good local guitarist & get a chance to try out this design. I'd love to have an amp like this if I could get that tone at about 15-20 watts, but that doesn't sound possibly.
I will post a layout for this by this wkend if not sooner.
Thanks, guys! I enjoy the interaction and thoughts! With respect, Tubenit
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diff-amp grid-leaks should be 270k? i'd use 470K. just because. :p
Oops, DL already said it. I thought I checked to make sure I wasn't repeating anyone, but I guess I need more sleep. :laugh:
Why not take it way on down? Maybe a pair of 6AQ5s? Call it Major Minor. :icon_biggrin:
Get it down to 7w. Then you could call it a "Minor Major 7". Perfect amp for your jazzy songs...
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something along the lines of what i'd build.
maybe the following as well:
a) up the values of the coupling and bypass caps on the ice-pick channel.
b) adding cathode fuses for each KT-88.
c) neg bias PS go/no-go mains lockout.
--pete
That's a nice looking print Pete!
Is there a problem with the way you have the FWB on the bias winding? :dontknow:
Looks like one of the AC legs is going to ground
Jeff, I definitely like his grid stopper on V2 pin 7
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Pete,
The top boost channel (your ice pick description!) is not bad at all. Those values would not work well in a normal 50 watt! I think it goes back to the overall design. The normal channel has a very full body response - if even a little boomy. I find the top boost very musical and manageable.
Jim
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Slightly OT, why did KOC referred to the differential amplifier as "paraphase", they aren't really the same thing, are they?
From TUT5, chapter 7, page 3;
"Since the UL connection reduces the effective gain or sensitivity of the tube, much more drive voltage is needed to get full output. Referring back to Mullard's own spec; in tetrode, -34V of bias on g1 with 67Vpp drive, versus -75V and 140Vpp in UL. To use the UL output stage will require something more than a Schmitt (LTPI) splitter.
The drive stage Marshall settled on was a paraphase stage. This is merely a differential amplifier that has differential drive all the time."
Brad :icon_biggrin:
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Slightly OT, why did KOC referred to the differential amplifier as "paraphase", they aren't really the same thing, are they?
From TUT5, chapter 7, page 3;
"Since the UL connection reduces the effective gain or sensitivity of the tube, much more drive voltage is needed to get full output. Referring back to Mullard's own spec; in tetrode, -34V of bias on g1 with 67Vpp drive, versus -75V and 140Vpp in UL. To use the UL output stage will require something more than a Schmitt splitter.
The drive stage Marshall settled on was a paraphase stage. This is merely a differential amplifier that has differential drive all the time.
Brad :icon_biggrin:
Another very informative post...
I gotta sell a couple amps and get me some of dem dare books :evil5:
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Any new OP UL tranny will work in this amp. Ed likes the Hammond, many Major owners have gone with the Heyboer replacement and have been really happy with no smoke issues. I think it would be very easy to replicate the original tone without blowing out the windows. Yes, speaker breakup and moving a lot of air contributes - as well as a tinge of KT88 distortion (the best!). But the full body response of the UL KT88's working with this unique preamp is awesome at any volume. You could run those tubes at 350v and have a great 60 watt amp with the OWM and PPIMV. Just because a car will do 150 mph, doesn't mean you have to go that fast. I've only found a few tube brands that work well in my amp. With that plate voltage and screens only .001v behind (with the original screen resistors), they get beat up pretty bad. Lower the B+ and just about anything out there will work. Ed has done a LOT of KT tube swapping with his builds, so I would defer to him on anything new. I'm still stuck on my =C=.
Hope this esplains it and debunks some myths. This is great to see! I have been beating the Major drum for years, it's good to see you guys running with it! :worthy1:
Jim, just a couple of corrections.
I prefer the UL OT from Triode. As a matter of fact on the last build (the best one yet) I simply used the whole set, PT, Choke and OT. The whole deal is $260 which may seem high until you get them. Lot of iron.
The Hammond feels tighter. In the amp I used the 1650N, which is 60 watt iron. It will get a little hot when cranking, but to me has a better feel than the Hammond 1650R which is really overkill for 2 tubes and the thing 10lbs. All things considered the A431S Dynaco to me worked best.
Now on the 12Au7 as the driver. Like I mentioned, the preamp is much different in the Route 66 and that is what I have used. I believe if I raise the voltage some in the preamp, I would not need much gain at the driver.
The Major is one of the few Popular amps I have never owned or spent much time with, but I am very familiar with the tone. I would think if you design from the prospective of reducing the ma on the PT and get voltage in the high for 2 tubes and copy the rest of the Major, it should sound very close.
I am not sure if lowering the voltage is a good idea, but I don't know for sure. The only comparison I have is between an amp out of a Leslie 147 I converted to run KT88 cathode bias. The difference is that it is not punchy. IMO the only reason to use KT88 is the punch. Sure the distortion is nice, but it is this punch I find in KT88's that I have not found in other tubes. To me this is the difference between 6550 and KT. The 6550 is really not a replacement for the tube as some say.
This thread caught my attention because I have been wanting to build a 2 tube Major myself, but I have been concerned if it can be done with 2 tubes. Like you said, it doesn't have to be turned up all the way all the time. I question it because a Marshall 4 tube EL34 IMO sounds better than 2 EL34.
Edit; Fixed quote, Willabe/Brad.
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Slightly OT, why did KOC referred to the differential amplifier as "paraphase", they aren't really the same thing, are they?
From TUT5, chapter 7, page 3;
"Since the UL connection reduces the effective gain or sensitivity of the tube, much more drive voltage is needed to get full output. Referring back to Mullard's own spec; in tetrode, -34V of bias on g1 with 67Vpp drive, versus -75V and 140Vpp in UL. To use the UL output stage will require something more than a Schmitt (LTPI) splitter.
The drive stage Marshall settled on was a paraphase stage. This is merely a differential amplifier that has differential drive all the time."
Brad :icon_biggrin:
Interesting background story for sure, alas, the use of "paraphase" to describe the differential amplifier used in the Major is an oversight... The paraphase or "see-saw" circuit has a distinctive feature, with one half of the differential pair getting its input from the output of the other half, as shown in the diagram below, whereas in the Major, each of the differential pair's inputs are driven from the previous cathodyne stage. :m20
(http://www.r-type.org/articles/art-097a.jpg)
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This thread caught my attention because I have been wanting to build a 2 tube Major myself, but I have been concerned if it can be done with 2 tubes. Like you said, it doesn't have to be turned up all the way all the time. I question it because a Marshall 4 tube EL34 IMO sounds better than 2 EL34.
And that could be the hitch in the giddy up right there.
From KOC's TUT3, chapter 7 (Plexi) page 5;
"A 100W model has 4 tubes contributing to the class-A region, and the transition to class-B is higher in power and slightly higher on the loudness scale. Some players feel they must have this articulation available, even though they can never hope to use 100W.
Other players find the sound of the 50W amp at reasonable-to-loud volumes is more "present". Although they do not know it, they are playing above the transition point to class-B operation. In this part of the transfer curve, the harmonics imparted to the signal by the output tubes is different than when the tubes are in class-A. We have a higher level of odd-order-harmonics which in small quantities contribute a sense of "attack', "crispness" or "fast response". Too many, of course, this will sound harsh."
The chapter has a build in it that Kevin calls the "5100" which is a 50w Marshall type amp that has 4xEL34's but only the power of a 50w amp. Pull 2xEL34 tubes and you have a 50w 2xEL34 Marshall clone, leave all 4xEL34 tubes in and you have the 'sound/feel' of a 100w Marshall but only at 50w because of the iron set.
IIRC, it was a very popular build over at his Power Scaling forum.
Brad :icon_biggrin:
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Interesting background story for sure, alas, the use of "paraphase" to describe the differential amplifier used in the Major is an oversight... The paraphase or "see-saw" circuit has a distinctive feature, with one half of the differential pair getting its input from the output of the other half, as shown in the diagram below, whereas in the Major, each of the differential pair's inputs are driven from the previous cathodyne stage. :m20
Kevin's a pretty sharp guy and I'd be very surprised that he would miss-name a simple circuit. He must have a good reason he referred to it as he did. :dontknow:
A further explanation is probably in 1 of his other TUT books somewhere but I'd have to go through 7 volumes and 100's of pages to find it.
Brad :laugh:
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Kevin's a pretty sharp guy and I'd be very surprised that he would miss-name a simple circuit. He must have a good reason he referred to it as he did. :dontknow:
A further explanation is probably in 1 of his other TUT books somewhere but I'd have to go through 7 volumes and 100's of pages to find it.
Brad :laugh:
KOC is really knowledgeable, that's why I seached through old books and papers to see where that reference came from, and I couldn't find any... Don't mind me, just geeking out a bit... :icon_biggrin:
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Kevin's a pretty sharp guy and I'd be very surprised that he would miss-name a simple circuit. He must have a good reason he referred to it as he did. :dontknow:
A further explanation is probably in 1 of his other TUT books somewhere but I'd have to go through 7 volumes and 100's of pages to find it.
Brad :laugh:
KOC is really knowledgeable, that's why I seached through old books and papers to see where that reference came from, and I couldn't find any... Don't mind me, just geeking out a bit... :icon_biggrin:
Maybe it's just in the wording....
It's not a paraphrase inverter that we're looking it....(because it's not the phase inverter)
But the driver section that it refers to 'could' be described as a paraphase amplifier?....maybe?
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Maybe it's just in the wording....
It's not a paraphrase inverter that we're looking it....(because it's not the phase inverter)
But the driver section that it refers to 'could' be described as a paraphase amplifier?....maybe?
Ahhhhh..... maybe.
Brad :icon_biggrin:
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Try to pull a fast one, eh?! :icon_biggrin: No, KOC call the driver stage "concertina" which is what it is. Here is what Brad posted:
KOC, TUT5, 7-6 , Marshall Major chapter;
"Note that placing the (MV) dual pot between the concertina and the paraphase (driver triodes) stages is no different than the single-section pot at the input of the concertina (in place of the grid leak R). This is because the concertina is not a gain stage and should not be considered as such.
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No, read my quote again, "between the concertina and the paraphase (driver triodes) stages", concertina 'feeds' the paraphase 'driver' stage'.
I left out the part where Kevin says the PI is a concertina to feed the paraphase.
I'm thinking SG's correct on this, it's a 'paraphase amplifier' not a 'paraphase PI'.
Brad :think1:
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Try to pull a fast one, eh?! :icon_biggrin: No, KOC call the driver stage "concertina" which is what it is. Here is what Brad posted:
KOC, TUT5, 7-6 , Marshall Major chapter;
"Note that placing the (MV) dual pot between the concertina and the paraphase (driver triodes) stages is no different than the single-section pot at the input of the concertina (in place of the grid leak R). This is because the concertina is not a gain stage and should not be considered as such.
No, KOC call the driver stage "concertina" which is what it is.
?
Maybe we're having a misunderstanding...
In this amp:
Phase inverter = concertina
Post phase inverter driver stage = paraphase (paraphase amplifier?)
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Don't mind me...
I just want to have a new acronym that I can use:
PPIPD
:l2:
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Maybe we're having a misunderstanding...
In this amp:
Phase inverter = concertina
Post phase inverter driver stage = paraphase (paraphase amplifier?)
You may be right, that he was simply using "paraphase" as a generic term to describe a differential amplifier, but that's rather unorthodox, as paraphase is usually associated with "phase splitter" - doing the duty of phase splitting and not just an "amplifier". See this (http://www.merriam-webster.com/dictionary/paraphase%20amplifier) definition for example.
PPIPD is a real PITA :laugh:
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as paraphase is usually associated with "phase splitter"
That's true in our small room of electronics. But when you open the door to the rest of the electronics industry, paraphase has a much broader definition. Still generally applies to the idea of two signals that are phase shifted by 180°.
As a side bar google "tube differential amplifier".
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Don't mind me...
I just want to have a new acronym that I can use:
PPIPD
:l2:
Got your PPIPD, PPMIV, MV, LTPI, PT, PA, OT, oddly enough we are still typing Choke which is guess is short for Inductor. What is PPPI? Maybe we can come up with enough where it looks like we are typing in code.
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Got your PPIPD, PPMIV, MV, LTPI, PT, PA, OT, oddly enough we are still typing Choke which is guess is short for Inductor. What is PPPI? Maybe we can come up with enough where it looks like we are typing in code.
That's "A OK" with me! 10/4 good buddy!
:icon_biggrin:
Tubenit
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Got your PPIPD, PPMIV, MV, LTPI, PT, PA, OT, oddly enough we are still typing Choke which is guess is short for Inductor. What is PPPI? Maybe we can come up with enough where it looks like we are typing in code.
That's "A OK" with me! 10/4 good buddy!
:icon_biggrin:
Tubenit
Breaker 19, Jeff you got your ears on? Be back gotta go 10/100, or maybe 10/200. Heres hoping. :laugh:
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This amp has turned into a :
'67, lite, OWM, TMB, CPI, PPIPD, PPIMV, CB (for tubenit), FB (for me), 2- KT88, UL OT @ 500+ into 4.2K
Edit: I left out 2 : SS + FWB
Sometimes, when I read DL's (and others) posts, I have to stop and think about what the abbreviations mean,,,,and I feel like a dummy :sad:
We should probably create a chart...
I needed one of these when I started texting with my kids :
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:l2:
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Sometimes, when I read DL's (and others) posts, I have to stop and think about what the abbreviations mean,,,,and I feel like a dummy :sad:
Join the club my friend. :laugh:
We should probably create a chart... I needed one of these when I started texting with my kids
Meh, texting, my wife does it with her kids and the other nurses at work. I got no use for it.
Wanna talk, call me on the phone!!!!!!! (Web site forum is different.)
And don't get me started on face book. :BangHead: :cussing:
Brad :l2:
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something along the lines of what i'd build.
maybe the following as well:
a) up the values of the coupling and bypass caps on the ice-pick channel.
b) adding cathode fuses for each KT-88.
c) neg bias PS go/no-go mains lockout.
--pete
That's a nice looking print Pete!
Is there a problem with the way you have the FWB on the bias winding? :dontknow:
Looks like one of the AC legs is going to ground
Jeff, I definitely like his grid stopper on V2 pin 7
fixed! thanks guys. i don't know why i make that mistake when drawing a bridge. i just do if over and over again! ugh! :-)
--pete
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the concertina is feeding a differential pair, sometimes called the long tail pair. IIRC this is one of the traits of the williamson design.
in this amp the tail is passive. audiofools like to add an active tail. they tend to make things far more complex than they need to be. that's just my opinion, not fact.
--pete
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Pete,
The top boost channel (your ice pick description!) is not bad at all. Those values would not work well in a normal 50 watt! I think it goes back to the overall design. The normal channel has a very full body response - if even a little boomy. I find the top boost very musical and manageable.
Jim
thanks, for the feedback jim. it is appreciated very much. this is an intriguing design.
do know of anyone who has tried the hammond 1650WA that i specified in my schema? sim shows PS will make about 550V B+ with the hammond 379WX. a well matched quad of =C= should be able to hold that back. i'd probably just use the quad of phillips branded GE 6550s i just acquired. i can't find anyone who stocks the heyboer marshall major 200W PT/OT sets. they must be custom order?
i plan on buying a couple of quad sets of the =C= before they dry up. after that, who knows what'll work...kind of feels like the 80's again; when US companies dumped tube mfg.
--pete
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Pete,
The top boost channel (your ice pick description!) is not bad at all. Those values would not work well in a normal 50 watt! I think it goes back to the overall design. The normal channel has a very full body response - if even a little boomy. I find the top boost very musical and manageable.
Jim
thanks, for the feedback jim. it is appreciated very much. this is an intriguing design.
do know of anyone who has tried the hammond 1650WA that i specified in my schema? sim shows PS will make about 550V B+ with the hammond 379WX. a well matched quad of =C= should be able to hold that back. i'd probably just use the quad of phillips branded GE 6550s i just acquired. i can't find anyone who stocks the heyboer marshall major 200W PT/OT sets. they must be custom order?
i plan on buying a couple of quad sets of the =C= before they dry up. after that, who knows what'll work...kind of feels like the 80's again; when US companies dumped tube mfg.
--pete
A 20lb OT and 28lb PT. WOW. No, I have not tried them. Sounds like fun, but I would need someone to help me get the things on my bench. :laugh:
Man you could build a 2 12 combo like a twin with 8 6L6 in it. Add a couple of JBL's and you would have one cool grab and go amp. :l2:
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Pete,
The top boost channel (your ice pick description!) is not bad at all. Those values would not work well in a normal 50 watt! I think it goes back to the overall design. The normal channel has a very full body response - if even a little boomy. I find the top boost very musical and manageable.
Jim
thanks, for the feedback jim. it is appreciated very much. this is an intriguing design.
do know of anyone who has tried the hammond 1650WA that i specified in my schema? sim shows PS will make about 550V B+ with the hammond 379WX. a well matched quad of =C= should be able to hold that back. i'd probably just use the quad of phillips branded GE 6550s i just acquired. i can't find anyone who stocks the heyboer marshall major 200W PT/OT sets. they must be custom order?
i plan on buying a couple of quad sets of the =C= before they dry up. after that, who knows what'll work...kind of feels like the 80's again; when US companies dumped tube mfg.
--pete
A 20lb OT and 28lb PT. WOW. No, I have not tried them. Sounds like fun, but I would need someone to help me get the things on my bench. :laugh:
Man you could build a 2 12 combo like a twin with 8 6L6 in it. Add a couple of JBL's and you would have one cool grab and go amp. :l2:
it would be of interest to know what reproduction iron weighs... ya 48Lb in transformer alone kind of makes me think about spinach and the gym...
--pete
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I could be wrong, but I don't think running a KT88 at 600v is necessary to reproduce what we are trying to achieve. Iron for a project like that is VERY high dollar. Run em at 350v and call it a day. We don't need the dB's or the wear and tear on the tubes and ears. I think the KT88 is one of the most beautiful sounding tubes when driven hard. If we starve them, we will get there sooner - but it should retain it's other characteristics I'm seeing at 600v. Cheaper iron and components. The KT88's are a big part of the overall mojo which is why I think the Park 75 sounds better than a Marshall 50 (same except for KT88's in place of the EL34's). However, the other half of the mojo is the preamp/phase inverter/driver interaction. I think this is very doable with some safe voltages and cheaper parts.
Jim
SG, you got this thing breadboarded yet!
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I could be wrong, but I don't think running a KT88 at 600v is necessary to reproduce what we are trying to achieve.
my thoughts are just the opposite but i do concur of the 600V B+. not with modern tubes. 500-550V is doable with modern tubes and i think that'll get us closer to the mojo of the major [is that a book title?]. new FLA - MOTM.
perhaps it would be frugal to build a 100W version, however, i'm of the opinion that the KT-88 pushed hard in UL is a significant part of the overall sound and that part of that "hits you in the chest" you describe is the probably acoustic wave of a 200W amp and there's no other way to replicate that. hot rodder's have an old saying; "there's no substitute for cubic inches". in this case, there's no substitute for wattage.
all this is just blather speak, so please flame away!
--pete
https://www.youtube.com/watch?v=Xc1PHk9FhIk (https://www.youtube.com/watch?v=Xc1PHk9FhIk)
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major minor - steve, i stole the name! ;-)
100W version. using the bias tap for the bias supply wasn't getting it done on the sim. added T2 - a 10VCT/120V xformer with FWB bias supply.
ok, i'll be quiet now.
---pete
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Jeff,
On your schematic of a 2- KT88 version, you can reduce the value of that 10 amp mains input fuse significantly (maybe half)
The final value will be based off of what B+ you wind up with, so maybe just leave the value blank and leave it up to the builder....?
If someone unknowingly builds it with a 10 amp fuse in there (just because your schematic has it on there), it won't provide the protection it was designed for....
...just a thought
:wink:
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SG, you got this thing breadboarded yet!
The good news is that my big board is clear.
The bad news is that I've got an amp that won't get off my bench, that is a must, for a guy who is waiting patiently.
I'm trading a sluckey TDR'ish for a PRS guitar :grin:
Sooooo, the suspense will have to continue......
I have been shopping for OT's because I think there might be something to the UL hookup..
I'm leaning towards the Hammond 1650N for a 2-KT build @ about 500V'ish (similar to Ed's)
DL, how do you like 4.3K @ 500V?
Anyone want to donate a couple used 88's to a good cause? :angel
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using the bias tap for the bias supply wasn't getting it done on the sim. added T2 - a 10VCT/120V xformer with FWB bias supply.
I'm thinking about using this PT for 2 tuber
The 60V bias winding with FWB should get me there....right?
http://www.classictone.net/40-18069.pdf (http://www.classictone.net/40-18069.pdf)
500mA HT should be enough for the 4 tube build....?
You could put one(or both) of the 15V windings in series with the bias winding to beef it up.....if necessary...?
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using the bias tap for the bias supply wasn't getting it done on the sim. added T2 - a 10VCT/120V xformer with FWB bias supply.
I'm thinking about using this PT for 2 tuber
The 60V bias winding with FWB should get me there....right?
http://www.classictone.net/40-18069.pdf (http://www.classictone.net/40-18069.pdf)
it'll work nicely.
500mA HT should be enough for the 4 tube build....?
probably. it'll be choking at max power. you'll need around 630mA at full power.
You could put one(or both) of the 15V windings in series with the bias winding to beef it up.....if necessary...?
one would be enough, likely not needed since you have a separate winding for the bias on the classictone PT - use a delon FW doubler if needed. bias will need to be about -75V at 550V B+.
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SG, you got this thing breadboarded yet!
The good news is that my big board is clear.
The bad news is that I've got an amp that won't get off my bench, that is a must, for a guy who is waiting patiently.
I'm trading a sluckey TDR'ish for a PRS guitar :grin:
Sooooo, the suspense will have to continue......
I have been shopping for OT's because I think there might be something to the UL hookup..
I'm leaning towards the Hammond 1650N for a 2-KT build @ about 500V'ish (similar to Ed's)
DL, how do you like 4.3K @ 500V?
that will work fine. anything from 4-5K for 2-tube or 1900-2200 for 4 tube, @ 500-550V. 2 tube OT will need to carry ~300mA/side. get the 1650NA not the 1650N - the non A suffix part has a convoluted secondary wiring scheme.
Anyone want to donate a couple used 88's to a good cause? :angel
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Cool..
THANKS DL!...I'll BB it first and see what's up...
At least I feel like we've demystified xfmr selection for anyone else who might be playing along
Down the line,,I'm thinking bout adding a tube loop, which will serve as my pre-PI master (yes Jim, I just said that :huh:)....no PPIMV
We'll see how it goes :dontknow:
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Thanks for the continued interest and info on this thread! I am working on a layout and will have that done by end of the wkend.
10A fuse issue noted. Thanks.
I personally like the idea of a two KT88 design idea with a UL OT and 400 or less volts on the tubes.
With respect, Tubenit
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I don't think it is a Paraphase.
It is a lower-level phase splitter (cathodyne/concertina) driving push-pull voltage amplifiers (no long-tail under). Well known from Williamson. For hi-fi usually you use lower-gain tubes for supersonic bandwidth (for intense NFB for hi-fi) and slap another gain stage before the cathodyne for enuff total gain and a place to put that NFB.
Also I don't see how Schmitt's name got on the long-tail pair. (There IS a Schmitt Trigger which uses long-tail connection, but that's different from an audio amplifier.)
I think Kevin is more of a good, smart, and enthusiastic technician than a painstaking historian. Go by the circuits, not by names that were invented (and often confused!) before he was born.
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drawing depicts PT and OT discussed thus far in this forum.
for the major-minor, i'll run with the dynaco A-431-S OT and the CT 40-18069
for the major-major, i'll run with the hammond 1650WA OT and the hammond 379WX PT
--pete
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V3 - 12au7?
http://el34world.com/Forum/index.php?topic=17530.0 (http://el34world.com/Forum/index.php?topic=17530.0)
Jim
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Hey Kiddies, look what I have. I was at Jeff Bakos Amp shop this morning and he gave me 300mg of schematics that have been confirmed and original.
Attached. We have a couple of values wrong. Screen R is 250 as sluckey suggested to me.
Also, I have a lot more and I am not sure how to get 300mg to Doug. FTP maybe? They are very nicely organized alphabetically with Fender and Gibson being in Separate files.
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That schematic has the same error on the PI and the missing center tap on the bias winding. It's no better than the first schematic in this thread.
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I don't think it is a Paraphase.
It is a lower-level phase splitter (cathodyne/concertina) driving push-pull voltage amplifiers (no long-tail under). Well known from Williamson. For hi-fi usually you use lower-gain tubes for supersonic bandwidth (for intense NFB for hi-fi) and slap another gain stage before the cathodyne for enuff total gain and a place to put that NFB.
For history of the Williamson, the MO Valve Co., as well the KT66 and KT88 see:
http://www.oestex.com/tubes/williamson.htm (http://www.oestex.com/tubes/williamson.htm)
As PRR points out, the PI and following driver circuit that follows is 100% Williamson (see schematics at linked site). I suspect that if you track down MO-Valve HIFI circuits from the mid-1960's, there is a MO-Valve HIFI circuit identical to the Major, starting at the PI and moving right including the UL OT.
The Major/MO-Valve story is very similar to the Sunn/Dynaco story that coincidently was happening at the same time in the US.
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That schematic has the same error on the PI and the missing center tap on the bias winding. It's no better than the first schematic in this thread.
I thought having the bias tap in the transformer description on the bottom left was a help. I am sorry, but I missed the error oin the PI. What is that error?
Nevermind. I see. I am using one of my old Dynaco ST-70's changing the voltages on KT=88 with a variac to see where the tubes sound best. Problem is I am sure the circuit is 90% of the amps tone and I am not very close. However I can report that a Ab763 pre with KT-88's sound really good. But this is close to Garcia, not Blackmore.
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Here are some other utoob vids for sonic reference. Riffguy, incredible player, has an awesome Marshall collection with a modified Major - no detail other than a master volume added. First clip I think he said preamp on 5 and master on 2. This seems to be enough to get the 30watt speakers to crunch.
Making noise with a Vintage Marshall (http://www.youtube.com/watch?v=w0GQTKHePzs#)
Jeff, this is for you. To prove how simply magical this amp is, it has transformed a Tele into something I can almost listen to.
SHUFFLIN' (http://www.youtube.com/watch?v=0BsopqoZyRw#ws)
And one more. Not a big fan of this (or the previous tele) because it has too much preamp crunch and does not let the rest of the amp work. I think the Michael R/T vid with the OWM and PPIMV sounds much truer to the amp opened up.
Mini Flying V pumped through a 200 watt Marshall (http://www.youtube.com/watch?v=H0KczjG2-uo#ws)
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That schematic has the same error on the PI and the missing center tap on the bias winding. It's no better than the first schematic in this thread.
I am understanding this to be referring to the copy of the "original" Marshall schematic and not the one I just posted?
V3 - 12au7?
Ah, got it! Thanks!
Note that I went with 1k/10w on the two KT88 OWM & PPIMV design per Jim's recommendation (especially since he actually owns a Major).
Does the UL on the OT drawing looking reasonably OK ??
Anyone see any errors on the layout matching the schematic?
With respect, Tubenit
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I could be wrong, but I don't think running a KT88 at 600v is necessary to reproduce what we are trying to achieve.
my thoughts are just the opposite but i do concur of the 600V B+. not with modern tubes. 500-550V is doable with modern tubes and i think that'll get us closer to the mojo of the major [is that a book title?]. new FLA - MOTM.
perhaps it would be frugal to build a 100W version, however, i'm of the opinion that the KT-88 pushed hard in UL is a significant part of the overall sound and that part of that "hits you in the chest" you describe is the probably acoustic wave of a 200W amp and there's no other way to replicate that. hot rodder's have an old saying; "there's no substitute for cubic inches". in this case, there's no substitute for wattage.
all this is just blather speak, so please flame away!
--pete
http://www.youtube.com/watch?v=Xc1PHk9FhIk (http://www.youtube.com/watch?v=Xc1PHk9FhIk)
DL, I would agree with you 100% ARRR,ARRRR (my best Tim the toolman Taylor written impersonation). HOWEVER, when I played out with this amp back in the 70's-early 80's the only time I was able to use all four cabinets was outside and in very large auditoriums. Otherwise I was toasting two paralleled Altair attenuators through one cabinet sometimes with one or two speakers hooked up because we were playing in 1000sq/ft bars with the owners yelling at us to turn down. The recordings I have posted recently all follow the same protocol: 1. Everyone but me must be out of the house - including the dogs. 2. The amp and cabinet are in an adjacent room with the door closed. 3. I don't believe any have been recorded with the volume above 4. 4. I have to wear headphones turned almost all the way up to hear the backing track while a play.
Do you see a problem here? This is like owning a vintage car that you spend more time working on than driving and spending lots of money on it because it's not really a sensible or reliable means of transportation, but you have it anyway because the engine or the styling is like no other. But dang does it sound awesome opened up.
So, my thoughts are we can recreate this mojo with the same parts - but have the result being a usable amp that someone could take to a gig and mic up, or use for practice without having the wife threaten to divorce you.
Does this mean I am getting REALLY old? :dontknow:
Jim
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I thought having the bias tap in the transformer description on the bottom left was a help.
No. The description is also wrong. There are THREE center taps on that PT. Look at the schematic I posted.
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Pete,
To use another automotive analogy: Small block = EL34 Big Block = KT88 Does not matter how fast you are going (volume), the torque is always on tap (KT88)! :icon_biggrin:
Jim
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my thoughts are we can recreate this mojo with the same parts - but have the result being a usable amp that someone could take to a gig and mic up, or use for practice without having the wife threaten to divorce you.
WOW!! Whoever you are that posted that, please return the true Ritchie200 to our forum. :icon_biggrin: :l2:
Oh yeah, and we knew it wasn't the real Jim when the Tele was plugged into the Major video was posted. Nice try, but we want Jim released and returned to the forum. He owes me a Shiner Bock once I get into St.Louis.
:m8 :m8
And no, we have a policy to not pay ransoms to kidnapped forum members. Sorry! :dontknow:
With respect, Tubenit
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That schematic has the same error on the PI and the missing center tap on the bias winding. It's no better than the first schematic in this thread.
I am understanding this to be referring to the copy of the "original" Marshall schematic and not the one I just posted?
I'm referring to the sch schematic you attached to your original post. You later removed that sch file.
The "most correct" original schematic first showed up in reply #3. It's the second link in that reply.
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Jim,
It is not really a matter of getting old. Before I built my amp room, I couldn't turn up a 15 watt to the sweet spot with anyone home. I know it is nowhere near the same as I have played a Major.
There is something to learn with this. It seems to me the Major has a clean, powerful power section. This has the ability to take whatever is in the preamp and reproduce it as transparent as possible with very little coloration. That is what the tube was designed for. This added to a UL OT, it has to be.
This is different than what a lot want, but it is rare to hear even 100 watt amps power tube distortion these days. Reason is clubs are smaller.
Back in the late 70's and early 80's we had mega clubs here in atlanta. MADD and tougher driving laws put an end to that as people were forced to drink closer to home. So welcome th "Cheers" you neighborhood pub, where you can play for tips.
And really, where could rock music go after Winger and Ratt?
What may be fairly cool is build the with 4, 6bm8 tubes for about 24 watts.
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Ed,
Yes, but.... The amp really shines when you start whipping those KT88's - as you heard in that California Jam video. Again, I think you could starve a KT88 and maybe get there? That's why I noted the difference between the regular Marshall 50 and the Park 75. Same amp different tubes - the Park sounds better.
KT88....did I mention KT88? Fellas, let's not stray from the path to nirvana.... :worthy1:KT88
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What may be fairly cool is build the with 4, 6bm8 tubes for about 24 watts
I think that is an interesting idea! The 6BM8 (two tube) amps I built were between 7-9 watts and I played one of those amps fairly regularly with a band that had a keyboards and loud drummer and it worked out when mic'd.
The 6BM8's actually have a decent bass tone for a small tube, IMO. I have used the 6BM8 triodes for an LTPI before but found I actually prefer using a 12A_7 for an LTPI with 6BM8's and only using the pentodes for the power amp and not use the triodes at all.
I'm also thinking that maybe a pair of cathode biased KT-66 tubes with the PPIMV might work?
with respect, Tubenit
the major minor jr.
--pete
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if i were to build one on the breadboard. please see attached schema. the discrete diode bridge is 8 uf4007.
would need to order the PT, the OT because i have a copy. likely will need to tweak the bias supply some.
--pete
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the major minor jr.
How 'bout Maj. PeeWee Marshall?
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If the objective to create something tolerable in sound level and keeping the performance of KT88s - without using KT88's then there's a whole host of power tubes at our disposal. But if having to use the KT88 as Jim suggests is absolutely necessary then using two is still too darn much power. The only option is to make a SE KT88 maybe with fixed biasing that "might" even come close to his jr giant or major minor wishes? But we're trying to run a big block V8 on only two cylinders and no matter what we decide there's just not going to be an equivalent to the original nor will it push the cones, etc. all the same. You all know this but please help me, what is the objective here? I know what I'd do or try but that wouldn't likely cut the mustard on Jim's hotdog? Maybe he has to have ketchup on his? :l2:
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the major minor jr.
How 'bout Maj. PeeWee Marshall?
that'll do! :-)
--pete
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Again, I think you could starve a KT88 and maybe get there?
OK, I am going to toss out an idea for discussion. I looked at Ed's voltage chart for the Major. I looked at my voltage chart for my Tweed
BluezMeister.
The preamp volts for my TBM are reasonably close to the preamp volts for the Major. The TBM PT is 300-0-300 and uses a GZ34 or 5V4 (depending on what I am in the mood for)
So, in light of that ......................... I think a PT that is 300-0-300 250 ma using a solid state rectifier would put about 420volts on the KT88's and then use a B+ rail of : Node A --- 1.5k --- Node B ---- 8.2k ----- Node C ------ 2.2k ------ Node D.
This should put about 420v on the KT88 plates and get around 235v on V1-6 (V1-b) and 190v on V1-1 (V1-a). (those are the Major's volts on the preamp plates)
So using this approach we get a lowered voltage on KT88's and have the preamp stuff stay somewhat similar to the original?
How do you guys feel about using cathode biasing? I have cathode biased 6L6's and if you use a pretty large cathode cap like 100uf to 220uf, it can get some pretty convincing fixed biased tones, IMO. Cathode biasing may help a little bit in reducing volume and allowing break up at a lower volume?
What do you guys think of the 300-0-300 PT to keep the voltage lower on the KT88's?? And what about the cathode biased idea?
I am thinking with a PPIMV and cathode biasing and maybe using a 40w Hammond OT that has ultra-linear wiring? I compared a 25w or 30w Hammond OT with a stock JCM900 50w OT and there was very little difference in size. Maybe we could capture most of the Major tone essence at a somewhat reasonable volume?
With respect, Tubenit
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Maybe we could capture most of the Major tone essence at a somewhat reasonable volume?
I don't like sounding contrarian but there's too many compromises therefore it's not the same thing and I think that's what Jim's talking about? Plus 420V would be your unloaded voltage, not w/ those 88s drawing current. The difference between fixed & cathode bias is a lot, there's even a difference between hot & cold fixed bias settings as you know in sound & feel. You'd still be able to make a sweet amp going forward with your ideas but I don't think it would pass the "major mustard" ultimately?! The best way to get there would just run the two 88's instead of four w/ ppimv and putting a volume after the tone stack keeping everything else about equal, IMHO.
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something I just found backing up Jimbo's claims on this beast from a puplication by Don Hunter
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I am thinking that "the" Major Marshall tone may be unobtainian at less then 80-100 watts? :dontknow:
Having said that, I am also thinking that some of the features of the Major like bottom end, crunch, pinch harmonics and sustain can still be gotten by compromising the original design into something else closer to 30-40 watts so it could be played at a club.
And who knows maybe messing with the design may come up with something comparable sweet or even better? (Keep in mind I've never actually cloned a manufactured amp so I am not a purist or cloner). Probably not many of us are playing large arenas and need 100-200w?
Looks like cathode biased at around 375v would yield around 40 watts!
http://www.triodeel.com/6550ap3.gif (http://www.triodeel.com/6550ap3.gif)
And this suggests cathode biased around 400v with ultra-linear would be around 30 watts
http://www.triodeel.com/kt88p3.gif (http://www.triodeel.com/kt88p3.gif)
I'd be more interested in a great sounding 30-40w Marshall amp that gives a reasonable nod to the Major's tone, then a Major that I never get a chance to play at all. Anyhow, that's may 2 cents of philosophy on this.
:icon_biggrin:
With respect, Tubenit
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I agree with your analysis T. There's really only one way for that to be had with those tubes unfortunately. I was thinking something as simple as 4 6V6s or 6aq5s, maybe even el84s but then the grids on those would maybe be a bit overly sensitive requiring another change from the original. I think the approach would be to keep as much the same as possible from the preamp through the pi and tailoring the PA to fit whatever PT's you decide upon. So, possibly minor change in values w/ pi through the pa sections only. Then voltages adjusted just for those as well. I think you'd end up with something close? I really like EL95/6DL5 which are like 3w each single ended for about the smallest pDiss tube you might consider. You might end up somewhere close to 15-18 watts with those. Anyway, using 9-pin sockets could allow you to try more various tubes over octal sockets...you know this already unless you'd want the standard two 5881s or similar? So are you in need of something 30 to 40 watts or 15 to 22?
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So are you in need of something 30 to 40 watts or 15 to 22?
No, but I'm thinking someone might definitely enjoy a smaller wattage version?
I'm not planning on building it any time soon. I've got the Tweed BluezMeister 14w -17w and the D'Mars ODS 23w and when I ponder about building another amp, I am not sure I can build anything else that I like as well as those? They sound really fantastic to me and they're pretty versatile.
I do think the Major project would be great fun though and a great sounding amp, so maybe someday I'll get around to it.
And I'd love to see someone else give it a go!
With respect, Tubenit
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what is the objective here?
I think it's a little different for each of us....
I have no doubt that DL will build a full blown version...be afraid,,,be very afraid :icon_biggrin:
For T (if I may),,,he is trying to come up with an "acceptable compromise" (hey there's another potential name---MAC (Major Acceptable Compromise),,,knowing that most people aren't building 100watt amps anymore.
The unfortunate part is that,,,however you work the numbers,,, you're still gonna wind up with a very loud amp. 60,70,80,90 watt amps are only going to be a few decibles away from each other.
We all know that there is only a small db difference between a 100 watt amp and a 50 watter, so for me the concept of a 2-KT88 build doesn't present a volume conundrum...I don't think i'll ever push it hard enough to get the full ride, and I don't think I'll have to, to be able to appreciate the sonic quality of this power stage arrangement.
BUT,,,after a few different attempts at trying to get a big beefy, thick, punchy tone out of some of the smaller variants (6V6, 6K6, EL84), I've found that they all eventually come up short.....no matter how much I like the tone, there is always something missing, and it's always in the bass response department.
The idea of a "golden tube" that carries the punch of a young Tyson is the most intriguing part of the story....I'm willing to trust Jim and Ed.
I feel like this specific tube represents the top of the mountain....and to never reach for the peak would be to never know that padre Jimbo was trying to lead us all to the sonic promised land. :m15.
Soldano was trying to sell us all on preamp drive into a clean power stage....he proved that to be a pretty darn good concept.
I see this project as taking that concept as far as it can go. (almost)
I'm hoping that I'll get some of the character of the KTs at lower volumes by limiting the input signal,,,and that will be a 'better' character than what you would get by trying to max out a lower power tube that never had the cojones to begin with.
MY T'ulator effects return pot will be my master.
P.S.
It's also pretty cool to see "the old guys" this interested in basically a 'metal' demo :wink: :headbang:
AND, it's great to see this schematic finally get fixed.
Maybe some day these damn kids will wake up and figure out that the tone that they hear in their headphones, can't be duplicated by a PC board,,,and the list of the best places to play your guitar doesn't include your bedroom.
Only then, will they come back looking for our accurate rendering of this work of art.
:d2:
You're welcome.
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Speaking of "I dont know who you are but bring back" ... SG!!! Well said young man! Thank you!
Jojo, single ended? Have I taught u nothing!!!
If you had some old gold lions you could really push them and get 120 watts out of a pair. You can also get 40 out of that same pair or maybe even 30 without losing sonic performance. Im sure Ed will concure that the KT88 is a special tube and I will say again that I believe it is intregal to the Majors magic. Heck if you bring it down low enough could you be in the wattage capability of power scaling for even more dB control? (I dont know enough about it to be dangerous...) Dont give up on this tube because you think it has to have 600v on the plates.
Jeff, I would sure like to see you build this. My offer still stands!
Jim
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Jojo
That article is yet another example of the Major misinformation on the web and in print. The Pig was completely diferent from the Major. The output section was not UL and very Marshall-esk in design. It had only three knobs and two inputs. It had active tone controls (bass and treble). They called it a Pig because of the huge cabinet with only about a 6" cutout for the knobs made it look like a pigs snout. It sounded completely diferent from a Major. Like I mentioned in an earlier post, only Ronson liked it and it was quickly put out to pasture.
Jim
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OK, here is my proposal ........................
OWM & PPIMV & cathode biased with 375 v on the plates. Based on my own Tweed BluezMeister B+ rail, I think I have made a reasonable guess on the dropping resistors for this idea. Should get pretty close to the right Major preamp plate volts?
I am understanding this to be 30 watts based on page 3 of this data sheet:
http://www.mif.pg.gda.pl/homepages/frank/sheets/086/k/KT88.pdf (http://www.mif.pg.gda.pl/homepages/frank/sheets/086/k/KT88.pdf)
Edcor has a 275-0-275 PT with 325ma that would work just fine and is reasonably priced:
https://www.edcorusa.com/xpwr004 (https://www.edcorusa.com/xpwr004)
With the 250uf (individual) cathode caps, I think it would emulate a reasonable fixed biased tone?
30 watts of KT88 tone!!! Thoughts!
Jim, weigh in on this idea, please! It's not purist Major 200w but perhaps a more useable & realistic amp that seeks to honor the KT88 Major tone?
With respect, Tubenit
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OK, here is my proposal ........................
That is very well thought out, and would appear to be the best working compromise...no matter what Jim says :undecided:
SG!!! Well said young man! Thank you!
:icon_biggrin:
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SG!!! Well said young man! Thank you!
:icon_biggrin:
This thread is having an affect on Jimbo like going to church, confession, or something??? :l2:
Okay my man - kt88's in a design such as tubenit's but w/out UL (if I'm reading you clearly?), w/ a vol after the tone stack (I think is necessary at least initially to control the total preamp vol/drive into the pi driver stage, and now VVR controlled output stage to corral the 88's even more?
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Okay my man - kt88's in a design such as tubenit's but w/out UL (if I'm reading you clearly?), w/ a vol after the tone stack (I think is necessary at least initially to control the total preamp vol/drive into the pi driver stage, and now VVR controlled output stage to corral the 88's even more?
I'm still thinking UL....(I was just gonna try the non UL OT cause I have one here,,,and still might just to compare the two)
I'm gonna try it a couple different ways once I make it to the BB,,,but I think t is onto something here
It doesn't appear to change the target primary K load much so i'm hoping to be able to get one OT and be able to have some consistent results with different voltages / bias situations....I'll want to see how much of an audible or feel difference tere is in cathode vs. fixed bias.
I'd really like to be able to try it both ways and give T some solid opinions about the differences to be heard.
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30 watts of KT88 tone!!! Thoughts!
With Rk of 470R, the KT88s are just cruising along and operating in near Class B, kinda defeats the purpose of using a large tube like this. Instead, I would bring down the B+ voltage down just a bit to suit the modern tubes, but pretty much leave everything else the same as the Major for a more faithful reproduction, there really isn't that not much difference between 30W vs. 50W SPL-wise, just me 2c.
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Setting aside Jim's odd eccentricities & dysfunctional obsession with strats & under appreciation of Teles, ...........................................
He actually owns a Major, so I think it's worth noting some of his "absolutes" with the Major. I think these should be included.
1) use of the 12AU7
2) UL is a factor
3) has to be KT88's
Some Hammond OT's have the option of UL or not UL. I am thinking one of the amp builds (some yrs ago) I did had a 30w 1650 that was about the same size as a JCM 900 50w OT. An OT with UL options would allow one to change away from UL if they didn't like it?
Hammond 1645 (30w) or 1650H (40w) could be options:
http://www.hammondmfg.com/1608.htm (http://www.hammondmfg.com/1608.htm)
And there is also this Edcor that could work with the Edcor PT:
https://www.edcorusa.com/cxpp30-ms-5k (https://www.edcorusa.com/cxpp30-ms-5k)
I thought about VVR, but prefer PPIMV ........... and I am not sure how about the VVR with a cathode biased version of KT88's? Maybe that would work long term just fine, but I don't know? Never had a problem with PPIMV.
With respect, Tubenit
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An OT with UL options would allow one to change away from UL if they didn't like it?
That's correct. Just cap off the UL leads. You'll have to supply B+ for the screens from a different B+ node, probably like most other amps.
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I thought about VVR, but prefer PPIMV ........... and I am not sure how about the VVR with a cathode biased version of KT88's? Maybe that would work long term just fine, but I don't know? Never had a problem with PPIMV.
Yep, would be less money & more simple for sure. Using or capping UL leads gives good option & comparison. UL seems like it would make for cleaner amp, not sure this would be needed w/ the headroom gained using 88s? (SG take note please). I agree w/ Jazbo in keeping as much of the preamp, driver, & pi areas as close as possible to the original. Where's Ed?
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So, my thoughts are we can recreate this mojo with the same parts - but have the result being a usable amp that someone could take to a gig and mic up, or use for practice without having the wife threaten to divorce you.
that's gonna be tough.
to get close i believe that we need to run a single pair upwards of 450-550V. the PT for a twin reverb will net around 450V B+ with a 4K load will yield about 70W in fixed bias in UL mode with around -60V to the grids. if we crank the load up to 5K we should be in 60W territory. not insanely loud but should be close. thoughts?
lastly, do you know what the preamp supply voltages are in the original?
--pete
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that's gonna be tough.
to get close i believe that we need to run a single pair upwards of 450-550V. the PT for a twin reverb will net around 450V B+ with a 4K load will yield about 70W in fixed bias in UL mode with around -60V to the grids. if we crank the load up to 5K we should be in 60W territory. not insanely loud but should be close. thoughts?
lastly, do you know what the preamp supply voltages are in the original?
--pete
+1
Preamp tube voltages from the Marshall voltage chart:
V1 = 235V, V2 = 300V, V3 = 310V.
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Correct V1 is 190v/235v. My Tweed BluezMeister with 275-0-275 is 188v on V1. That's why I suggest the B+ rail that I did.
As a side note, when I had VVR installed in amps and found a "sweet spot", I was always somewhat surprised at how low the voltages would be on plates and screens of the power tubes.
With respect, Tubenit
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that's gonna be tough.
to get close i believe that we need to run a single pair upwards of 450-550V. the PT for a twin reverb will net around 450V B+ with a 4K load will yield about 70W in fixed bias in UL mode with around -60V to the grids. if we crank the load up to 5K we should be in 60W territory. not insanely loud but should be close. thoughts?
lastly, do you know what the preamp supply voltages are in the original?
--pete
+1
Preamp tube voltages from the Marshall voltage chart:
V1 = 235V, V2 = 300V, V3 = 310V.
i believe that those underlined are the voltages plate and cathodes, screens etc. i was asking for the supply voltages. IOW, i'm asking for the voltages on TOP of the anode resistors? maybe i should have just said the "voltages of the power supply rails". :-) please don't be offended b/c i'm a dumb-ass.
my math + logic sucks... but here goes.
Ib of V1a = 1.75Vk/820Rk = 2.1mA
we have 190V indicated at Va. Vese of Ra + Va = supply rail voltage.
Vese of Ra= Ib * Ra = 2.1mA * 100K = 210Vese of Ra
so then 190V (from chart) + Vese of Ra = 210V + 190V; then supply rail ~400V.
Ib of V1b = 2.4V/2.7K = 889uA
we have 235V indicated at Va. Vese of Ra + Va = supply rail voltage.
Vese of Ra = Ib * Ra = 889uA * 100K = 88.9V
so then 235V (from chart) + Vese of Ra = 235V + 88.9V; then supply rail ~323V.
variance in mu between the sections, part tolerance, meter/measurement tolerances, etc., since there's a delta of ~77V in the supply rail calculations above.
now the V2 concertina:
chart shows VRk = 75V.
Ib=VRk/Rk = 75V/102.7K ~ 750uA.
chart shows Va @ 300V.
supply rail V is Vese of Ra + Va
Vese of Ra = Ib * Ra = 750uA * 100K = 75V
so then supply rail is Vese of Ra + Va, then 75V + 300V; supply rail ~375V.
for V3 - diff amp.
chart shows 15V VRk for 2 Triodes, sections a and b with a shared Rk.
so then Iba+b 15V/1.5K = 10mA so each triode is flowing 5mA
supply rail is Vese of Ra + Va. Vese of Ra = Ib * Ra = 5mA * 47K = 235V
so then Vese of Ra = 235V + Va = 310V; then supply rail ~545V
even with the variances of supply rail calculations of V1 compared with V2 concertina, we can assume the supply rails are probably upwards of around 400V. i was hoping jim could get us closer to the bulls-eye. the concertina has a AV of around .97 so calculations for supply rail should be closer to actual.
--pete
chart attached is what i was working off of.
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Jojo - WTH!?!??!?! What, you shred so hard you broke your stick?!?! I NEVER said anything about not using UL!!! I still think UL is a must. Yes, the tube is inherently clean and full, but I think the UL design is a big part of the package.
Pete and Jazbo, I realize we are wasting the power capabilities of the KT88 - it's like asking a Ferrari to drive in a parade. However in this case, we are looking for the tonal qualities of this tube, not the power. I like Jeff's 30watt idea. The Ferrari still looks good going slow! Again, I think we can replicate the qualities of the design without the wattage. If that means we can push these tubes into distortion at a reasonable volume, that is a fantastic win/win.
Pete, sorry I am the dumbass. Looking at the charts I do not see a problem running this tube at such a low plate. What am I missing?
Jim
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i was asking for the supply voltages. IOW, i'm asking for the voltages on TOP of the anode resistors? maybe i should have just said the "voltages of the power supply rails". :-) please don't be offended b/c i'm a dumb-ass.
I see now, you wanted the supply rail voltage, not the operating voltage of the tubes, anyway, we are looking at the same chart, so I think your calculations are spot on.
To Jim - As for the Ferrari analogy, I get what you are saying but sports/high performance cars are meant to be driven at the edge - they could tool around town, but it's not what they were designed for, since even a SMART would suffice.
Looking at the Major's design, I believe part of the sound comes from the headroom that the KT88 offers, i.e., it takes a lot of swing from the differential pair driver to clip its grid, so most of the time the output stage is running clean. If you reduce the B+ supply, two things happen, the bias voltage for the KT88s are lowered, so it takes less drive to clip it, resulting in reduced headroom, and if you do not make further adjustments to the rest of the circuit, the interplay between the various stage may skew the clipping/OD characterisitcs of the preamp and PI, which may still sound good, but perhaps no longer "Majorish". That's why I am still with Pete on keeping the voltages intact, if you really want to dial it down, then by all means, use the VVR and/or PPIMV.
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There has been some great discussion here! And I appreciate the thoughts, observations and math by everyone.
I trust Pete's math calculations to have 545v on the power rail to maintain the original voltages. And I think Jazbo8 has a reasonable argument that lowered voltages would compromise "the" Major tone.
I think a significant amount of my hearing loss came from playing a 50w MusicMan and a 33w Carvin amp. That is why I have a 14-17w & 23 watt amp now.
Even with those amps, I never have the volume knob past "5" and I have PLENTY of headroom left with 5881's. That's why both amps have overdrive channels that have great overdrive and very moderate volumes. I am not going to have an amp that has to be ear bleeding loud to get overdrive.
In fact, when I was weekly playing with a band (for 4 yrs until a couple of yrs ago), I used my Tweed BluezMeister with 6V6's 14 watts and a HoSo56 that had 6BM8's pushing maybe 9 watts. Yes, the amp was mic'd into the PA but honestly I had enough headroom even with a keyboard and a loud drummer.
Playing at home and playing at small venues, I am not worried at all that a 30w cathode biased version will not have enough headroom and be too distorted. I can not imagine not having enough headroom even playing in a small club with a 30w version?
IF you are wanting a 60-80w version of the "original" tone, then go with the higher 500v power rail. I don't think a PPIMV will control the volume enough for playing at home?
IF you are want an amp that is on the edge of the cranked KT88 tone and still has plenty of headroom for playing at home AND somewhat honors the Major tone without cloning it, then I will argue for the 30w cathode biased version.
Remember the version I am proposing has a switchable "one wire mod" to help achieve both a clean and an overdriven tone at lower volumes.
Again, I am NOT a cloner so I don't think in those terms. My thinking is maybe we can come up with something similar in tone to the Major but with a much more useable volume so someone could actually get to play it. And who knows, maybe it would totally sound incredible and create a tone that is even "better". What I mean by that, is this idea may sound "better" then the 200w Marshall at volume levels at home and in small clubs.
Anyhow, that is my thinking! Even with the PPIMV, a 60 watt version would never get played at my house. And if you went the VVR route then you've simply reduced the voltage on the power tubes and phase invertor which is what I am arguing for to begin with.
The original schematic uses a 25k resistor between nodes B and C and a 10k resistor between nodes C and D. Start with a lower voltage on the power tube plates and simply use smaller dropping resistors on the B+ rail to get voltages as close to original on V1 and V2. I think this will work out OK and sound great.
With respect, Tubenit
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I agree with everyone,,,,even Jim :sad:
This is the comment that I most associate my own thinking with:
Again, I am NOT a cloner so I don't think in those terms. My thinking is maybe we can come up with something similar in tone to the Major but with a much more useable volume so someone could actually get to play it. And who knows, maybe it would totally sound incredible and create a tone that is even "better". What I mean by that, is this idea may sound "better" then the 200w Marshall at volume levels at home and in small clubs.
And that's how I will approach it....the BB is a beautiful thing for that reason....no rules, and no layout necessary!
Only problem for me right now is that a pair of 88s and a UL OT are out of my reach, so I won't have any results anytime soon.
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To me, the simplest way to replicate the tone and feel of the amp that I like is to clone it with minor mods, which reduces the guess work involved. Since this whole thread was carried over from the Youtube clip thread, perhaps I am adhering too much to the original Major design, also I am not as creative as some of you guys here. :sad2:
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To me, the simplest way to replicate the tone and feel of the amp that I like is to clone it with minor mods, which reduces the guess work involved.
I agree with you. That definitely would be easier and come closer to making sure it is as close to the Major tone as one could get. Very appropriate response and thinking. My concern is the volume playing at home.
Let's guess that a two tube "original" version would capture 93% of "the" Major tone. That could be a fantastic choice for someone!
Let's guess that a two tube cathode biased 30 watt version would capture 62% of "the Major tone and then add 38% of another type of great tone. Between those two, I'd rather have the 30w version. Just a preference thing.
With respect, Tubenit
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So who's going to build one first? :icon_biggrin: I got quite a few projects in the pipeline (not all guitar amp related), so definitely not me... Anyway, I guess the concept of a mini Major has been around for awhile, see this (http://www.marshallforum.com/marshall-amps/14939-mini-major-project.html) for example, so your 30W version might just be taking the idea to a new direction afterall.
Audio Amp Co.'s RBMM:
(https://dl.dropboxusercontent.com/u/1326040/RBMM.png)
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I thought about VVR, but prefer PPIMV ........... and I am not sure how about the VVR with a cathode biased version of KT88's? Maybe that would work long term just fine, but I don't know? Never had a problem with PPIMV.
Yep, would be less money & more simple for sure. Using or capping UL leads gives good option & comparison. UL seems like it would make for cleaner amp, not sure this would be needed w/ the headroom gained using 88s? (SG take note please). I agree w/ Jazbo in keeping as much of the preamp, driver, & pi areas as close as possible to the original. Where's Ed?
Just watching my brother, just watching.
I already have a 2 tube KT88 and I cobbled together a very similar preamp. Running Valve Art KT-88 now for over a year at 569 v on the plates with NO problems at all. I ran some KT-120 and still have them. The KT-120 holds together better, but the Valve Art tubes I can get into distortion fairly easily.
Maybe it can be done in a lower wattage, but 80 watts sounds damn good. What is the difference in loudness between 30 watts and 80 watts? Not much except if you have a cabinet sitting on the floor and Hammer an E chord it will knock your feet out from under you. :l2:
I believe you can make an amp sound similar. Sort of the similarities a Deluxe as opposed to a Twin. I much prefer the Twin, but the Deluxe is nice.
If the intention is to get the power tubes distorting, it is impossible to make a 6L6 distort like a KT88 and not get loose on the bottom. We like that, well most of us. It is difficult to describe the difference.
Still, using the MV it is preamp distortion which is cool. I mean, that is what a tube overdrive is anyway.
Consider why the KT88 was designed. I may be wrong, but I believe it was designed as a way to get more wattage while still having characteristics of the KT66. Something I read, probably crap, but if power tube distortion is an absolute I do not see how to get it running the tube (KT88) with less voltage is going to provide this easily.
KT88 tubes are not 6550 and are easy to tell apart in a blind test if distorting, however the distortion is different. It is different than anything else so I cannot compare, but here goes. It makes your guitar feel like a powerful tool. the Tim Taylor is a great description.
I tried it with a SE amp I have as well. Could be a path to another good design, but the distortion is much less controlled. I hate to think this way, but I believe you are not going to get that badass tone from a wimpy amp. :icon_biggrin:
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Maybe it can be done in a lower wattage, but 80 watts sounds damn good. What is the difference in loudness between 30 watts and 80 watts?
I have no doubt the 80 watts sounds incredibly good! No argument there. Simple & honest question: Where and how often can you play 80 watts at the levels you like?
I certainly think there is a significant difference in volume between an 80w amp cranked and a 30w amp cranked.
And my best uneducated guess is that the PPIMV will control the volume to acceptable levels of volume at home on the 30 watt and that the same PPIMV won't control the volume enough on an 80 watt amp? Again, I acknowledge this is simply a guess? I could be dead wrong on this? I don't care for the PPIMV below that 3-4 range on the amps I've tried.
My understanding is the Dumble amps can get a pretty decent OD at close to bedroom volumes, BUT they have ALOT of preamp overdrive going on and not much power tube distortion taking place. .
Remember this idea we're talking about has a switchable one wire mod (OWM) and PPIMV. I think that combination with 30 watts will get the volume to a more reasonable level and still sound good? The OWM will allow some preamp overdrive to be there, IMO. So the OWM adds overdrive and the PPIMV lowers the gain to the power tubes so we don't have to push them so hard to get overdrive. Adding some preamp & lessening some power amp OD.
With respect, Tubenit
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Maybe it can be done in a lower wattage, but 80 watts sounds damn good. What is the difference in loudness between 30 watts and 80 watts?
I have no doubt the 80 watts sounds incredibly good! No argument there. Simple & honest question: Where and how often can you play 80 watts at the levels you like?
I certainly think there is a significant difference in volume between an 80w amp cranked and a 30w amp cranked.
And my best uneducated guess is that the PPIMV will control the volume to acceptable levels of volume at home on the 30 watt and that the same PPIMV won't control the volume enough on an 80 watt amp? Again, I acknowledge this is simply a guess? I could be dead wrong on this? I don't care for the PPIMV below that 3-4 range on the amps I've tried.
My understanding is the Dumble amps can get a pretty decent OD at close to bedroom volumes, BUT they have ALOT of preamp overdrive going on and not much power tube distortion taking place. .
Remember this idea we're talking about has a switchable one wire mod (OWM) and PPIMV. I think that combination with 30 watts will get the volume to a more reasonable level and still sound good? The OWM will allow some preamp overdrive to be there, IMO. So the OWM adds overdrive and the PPIMV lowers the gain to the power tubes so we don't have to push them so hard to get overdrive. Adding some preamp & lessening some power amp OD.
With respect, Tubenit
I can play at any volume I wish at anytime I want, but not outside my amp room. Since I do not play clubs anymore, I would guess I would use 100 or more watts maybe 10 times a year, however I did build one that gets used 4 to 6 nights a week.
I know what you mean, but I believe around the house you either have to be happy with preamp distortion via a MV or VVR or use a very small amp. I prefer master volume over VVR's, but each to his own. Even 15 watts sounding good is too loud for home. Push Pull tube amps in general are. For instance, the Delta speakers you are using are 400 watt speakers. Full range with a Xmas of 2.40mm.
Stay with me I know this is not a speaker discussion. My point is the speaker itself is designed not to color the sound or as little as possible, so on a 30 watt amp and that speaker you should be able to hear the amps tubes churning without speaker breakup. How loud is 30 clean watts? Ask Willabe about playing 15 watts in his garage and the neighbors complaining. 15 watts :dontknow:
The only amp I have that I can get power tube distortion with decent tone from is a sort of 5C1 build pushing a paper voice coil 15 watt where I have a nice marriage of speaker breakup combined with the tube distortion. I did have to add another gain stage prior to v1. I used a 5751. Even this amp is too loud for a lot of folks. The truth is unless you play, most people do not like the sound of an electric guitar screaming by itself.
So as Jojo said, there is give and take. Building an amp like this is expensive. Where is your sound coming from? PUPS like TV Jones with a dash of boost and a dirty channel ripping speakers breaking up all over with a sprinkle of power tube, but mainly preamp distortion. If it were this formula, I would not choose KT88's to do it.
Here is hoping it can be done. Even 66% there would be great. I just do not see anything that different in the preamp of the Major. Maybe the collective elements in the circuit make something like a special sauce, which is usually the case. That is why I chose the Route 66 preamp because I wanted easier distortion and was willing to not have that BEAUTIFUL Marshall Major clean tone which I feel is the greatest asset of the amp.
The old Ampeg flip-top B-15 sound great but on a 5 string cannot carry the low "B" cleanly. Solution, add more tubes or SS in most cases.
From all the goofing around I have done with the KT88 tubes, it is these lower harmonics that are a constant. I am sure some beneficial info is coming from this thread. I simply prefer the sound of speakers moving air and it is nice to have loads of volume when the drummer is killing me with the snare. Turn that baby towards him and ROCK!!
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Okay, for some additional sonic reference, I give you:
Made in Japan. The one wire mod had been done by Marshall (with light bulb "limiters" used in the preamp section on V1 to cut down on excessive feedback at high volume - not a tone changer). This is the Major showing it's stuff. From the sparkle of the chords at the beginning to the bomb blast at the beginning of the lead to the distorted, yet clear, yet distorted, yet clear lead runs. This (what I call) slashing distortion occurs when the KT88's are working hard. I think this is what Ed was trying to say about the unique nature of KT88 distortion and what makes me love this amp. How many amps give you that perfect drive on the chords yet wimp out on the lead without boosting? Or how many amps sound awesome when playing lead and then mush out into something non-musical deathmetalish with a power chord? To use another automotive/motorcycle analogy - when this amp is on pipe, it is a magical experience. Plus what you are hearing is a stock block strat straight in - not an easy feat.
Highway Star - Made in Japan [The Remastered Edition] (http://www.youtube.com/watch?v=gdzR4LzRwzQ#ws)
California Jam. This was two years later. Marshall's mods are still in place. Ritchie was looking for a little more front end drive. he found it with an Aiwa TP1011 reel to reel. There were only 50 examples made of this model and they fetch many thousands on Fleabay. Ritchie modified his to provide a slapback at the speed he wanted and found that turning up the preamp provided a perfect match for the front of the Major. He still has this unit and uses it in the studio and on stage. This is another magic moment as the amp is blazing with those KT88's working hard and that slashing distortion again - but with a little more top end (from the reel to reel). At the beginning Ritchie hits a chord and walks off to the front of the stage about 45 degrees away and maybe 50-60ft away from his cabinets. This is outside on an open stage and it is feeding back like crazy - that's how loud this thing is.
Deep Purple - Burn 1974 HD (Live in California) (http://www.youtube.com/watch?v=bMUJkauJ-mM#ws)
So why am I posting these? I absolutely love the Made in Japan tone - probably because I heard it live in 1972, its what drove me to spend every penny I had to buy one in 1973, and its the tone I've been able to recreate - at crazy volume. Like Ed said, it's like wielding a power tool or more appropriate - Thor's Hammer. The California Jam tone reminds me a lot of Michael's tone in the video I first posted that generated all this interest. That is why Ed made the comment about how can a Les Paul sound like Burn. Is it good, you betcha! Still better than any other amp (IMHO). However, if you notice, Michaels tone - while close - is not quite the same as the Cal Jam. THAT missing secret sauce are those KT88's working hard.
So, that is why I am pushing for that 30 watt version. Lower plate voltages will make it easier to get the KT88s "on pipe". If you can recreate Michaels efforts, you can always dial back the gain and treble and still get that MIJ tone that I love so much. Again, this is all my personal opinion and I'm sure yall have others for this amp. YMMV!
Jim
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regarding the notion of lowering the B+ voltage and hoping to get the same sound as the higher voltage Major, I'm reminded of the attempt that many have tried and failed to convert Sound City amps into Hiwatts. It seems tempting, there are those imposing great partridge transformers, a nearly identical layout, chassis, and build style, very very similar power section design and phase inverter section, and well, it seems the only difference is the preamp... So, gut the SC's preamp, install a Hiwatt preamp, and voila~!! right?
I once thought this too!! but the part of the magic of the hiwatts, and what significantly separates SC's from Hiwatts is the voltage on the plates. BIG PART!!!
The 6xEL34 Hiwatt DR200 has 650V on the plates, the 5xEL34 SC LB120 has 375V. No where even close! a LB120 with a hiwatt preamp != DR200. The same with all the others. the only one that might come close is the SC LB50 @ 420V and the DR506 @ 460V.
if you lower the voltage, reduce the tube count, etc... you might end up with a nice sounding amp, but I doubt it'd be a miny Major. build the real thing, send the family to see Frozen-II, lower the shades.., etc..
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if you lower the voltage, reduce the tube count, etc... you might end up with a nice sounding amp, but I doubt it'd be a miny Major. build the real thing, send the family to see Frozen-II, lower the shades.., etc..
HAHA! I do that already!
I guess what peaked my interest was that Michael R/T is playing his amp in what basically looks like a closet. I guarantee you that the master is on 1. SOOO, he was able to get incredibly close to the Cal Jam tone at an incredibly low volume with the OWM and PPIMV. My thoughts were that if we could get a power section that was controllable, we could have a REALLY cool thing. Will it sound exactly like the videos I just posted - no way to my ears. But I'd be willing to bet we have the folks here to push, pull, swap, and tweak to get it sounding pretty darn close, and I'd be willing to bet that only a very small handful of people could tell the diference. Yes, my pants flapping in the 625v on the plates dB breeze was golden and there is no substitute for big tubes working hard and speakers moving a lot of air, but that breeze also grabbed some of my hearing.
Speaking of Hiwatt (besides the many, many variations of circuits for the same amp), if you notice in the Cal Jam video, Glenn Hughes is playing through two 200watt DR201's (KT88 versions) on top of those huge reflex bins. Ritchie's amp tech told me that he could not turn them up past 6 or 7 because those open frame Partridge tranny's would feed back. As awesome as the stacks looked, he was not very loud at all. Keith Emerson had the same problem with his. Early design flaw? Another useless factoid rattling around in my head...
Jim
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> I can not imagine not having enough headroom even playing in a small club with a 30w
Then grab Dyna 35W iron. It is very fine quality. It has UL taps. Dyna worked two EL34 pretty hard, but 6550/KT88 can be used the same way (bit more G1 bias and drive). Dyna 35s are good hi-fi amps but they are also fine PARTY!! amps with a pleasant distortion.
Dyna had an all-purpose driver, which is fine, but I think for your purposes you may as well stay with the Major's driver.
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I guess what peaked my interest was that Michael R/T is playing his amp in what basically looks like a closet. I guarantee you that the master is on 1.
Here is MichaelR/T's settings used on the videos: " I plug my guitar into channel II then turn Channel I and Channel II volume up to 10, then keep the (PPIMV) Master Volume around 4 to control the overall volume. Than to add extra gain and crunch I use a 1/4 male jack only with no cable attached to it. I take this plug and stick it into channel 1 jack (high or low) and "bingo" it bring the amp right over the top in gain." from here (http://www.rig-talk.com/forum/viewtopic.php?f=3&t=146114#p1683220).
So with PPIMV on 4, the the output stage would be nowhere near clipping, what we hear is nearly all preamp distortion (pretty much square wave), so that begs the question, just how much do the KT88 and the UL OPT contribute to the tone? 5%? 10%? Who knows...
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I prefer this tone.
Child in time (Made in Japan) - Blackmore's solo (http://www.youtube.com/watch?v=kEc0LZFTSA8#ws)
Here is the Reel to Reel tone, but with killer vocals. Love this lineup.
Rainbow - Stargazer (http://www.youtube.com/watch?v=rVXy1OhaERY#ws)
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I prefer this tone.
Me too....
So much so that I skipped lunch all week and pulled the trigger on some toobs :icon_biggrin:
You guys will have to tell me if I made a mistake or not, because I got a little trigger happy with a NIB pair of Mesa Boogers for $50
And I have no point of reference to compare them to :dontknow:
At least they may have been matched/tested by someone with a Mesa T-shirt on....that's gotta be good for something right?
:happy1:
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SG
Well, the net says they are either Russian or Chinese - you are welcome for that info! :laugh: The net also says they are good solid toobs, but nothing to write home about tone wise, or they are really good, or they are just ok - you are welcome for that info too! They do say that Mesa does have a pretty rigorous testing procedure. And $50 a pair is a deeeeel! If you are going to use Jeff's lower plate voltage, even the crap will live a long life. The mesa's are running mid 500v so these have to be pretty decent.
Here is another example of my favorite things!
Jim
Lazy - Deep Purple [Made in Japan 1972] (Remastered Edition) (http://www.youtube.com/watch?v=tiWSrvWHQf0#)
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that was one of my favorite wake_n_bake albums...
--pete
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Pete,
You forgot the munch! I think this is the best live album ever. If you listen to it in it's entirety, you can certainly get a sense of how incredibly diverse, talented, and tight, the MKII version was. Just incredible.
Ok, not to duplicate, but I think this is important. The first Cal Jam Burn video I posted was from the ABC video feed probably pulled off the board. The show was simulcast on a local FM station who had placed several mics on stage. Some guy synced up the video with the radio station's audio feed and posted it. If you listen close you can tell a HUGE difference in Ritchie's Major tone as the radio stations mics actually sound much better than the compressed, flat sounding video feed. This is a MUCH better reference of the Major's tone at the time.
Jim
Deep Purple / Burn / 1974 California Jam (http://www.youtube.com/watch?v=8MLgxhqWLHo#)
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One more with some really good solo stuff.
Deep Purple / You Fool No One - Mule / 1974 California Jam (http://www.youtube.com/watch?v=8Bc3V9ceGKI#)
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At least they may have been matched/tested by someone with a Mesa T-shirt on....that's gotta be good for something right?
:happy1:
More than good for something... :icon_biggrin:
(http://www.meinlshop.de/images/product_images/popup_images/s/mesa-boogie-t-shirt-girlie-ringer-5515w-m-5515w-m_0.jpg)
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that was one of my favorite wake_n_bake albums...
--pete
So you no longer listen to Deep Purple during morning activities. :icon_biggrin:
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no sir i don't. i got burned out.
pun intended. :icon_biggrin:
--pete
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At least they may have been matched/tested by someone with a Mesa T-shirt on....that's gotta be good for something right?
:happy1:
More than good for something... :icon_biggrin:
(http://www.meinlshop.de/images/product_images/popup_images/s/mesa-boogie-t-shirt-girlie-ringer-5515w-m-5515w-m_0.jpg)
Questions: are they a matched pair, self biased, ultra linear, any negative feedback? :happy2:
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Hi guys,
I wanted to contribute my experience with a 2xKT88 Major build that I've had for the past two years. I was directed to this thread by a friend of mine who is thinking about building one too. After considering the RBMM route for a while I decided it was going to cost me too much so I commissioned it to the guy who showed the most enthusiasm about the project, Union Jack Amps in Seattle. I'm very happy with the quality of the build and the amp's sound. These are the specs I gave him FWIW:
- 2xKT88 (Gold Lions for now)
- 2xECC83 + 1xECC82
- UL MM OT
- Lead circuit
- PPIMV
- OWM (added later)
- Variable Negative Feedback.
After several sound tests I ditched all other forms of lowering the amp's volume in favour of the Rivera Rockcrusher and an isolation cab I made for less than $150. Nothing sounds better in this amp to my ears than pushing those KT88 to the max. PPIMV won't give you that. The OWM is too noisy and the distortion is too wild. I never use it. IMO this amp sounds at its best like Blackmore used to play it: With treble boosters (MKII) or the AIWA preamp (MKIII).
Here are two sound tests I recorded using the original Machine Head backing tracks and a Hornby Skewes booster that I built. I hope you guys like them:
http://youtu.be/RyeWVwsDVhQ?list=UU2MhqnWNx1yl5Qr3bLjdy0g (http://youtu.be/RyeWVwsDVhQ?list=UU2MhqnWNx1yl5Qr3bLjdy0g)
http://youtu.be/M6pljHMnHe0?list=UU2MhqnWNx1yl5Qr3bLjdy0g (http://youtu.be/M6pljHMnHe0?list=UU2MhqnWNx1yl5Qr3bLjdy0g)
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After several sound tests I ditched all other forms of lowering the amp's volume in favour of the Rivera Rockcrusher and an isolation cab I made for less than $150. Nothing sounds better in this amp to my ears than pushing those KT88 to the max. PPIMV won't give you that. The OWM is too noisy and the distortion is too wild. I never use it. IMO this amp sounds at its best like Blackmore used to play it: With treble boosters (MKII) or the AIWA preamp (MKIII).
Max - welcome to the forum! Thanks for the contributions, the tone sounded pretty spot on. I especially like the Lazy vid example and playing.
You also confirmed what I'd been saying about trying to make it differently yet expecting the same or even similar sound & performance. It just isn't the same. If one realizes this and is okay with it then great. But it's not reasonable otherwise.
For me in my Dumble & 18watt builds putting extra gain stages in didn't an amp make. They became one trick ponies. But if that's what someone wants is a bedroom or special recording amp full of gain, then fine. But, they don't make for practical performing amplifiers. All that gain just isn't practical or useable in a performance setting.
Just as Jim keeps insisting on the use of KT88s, doing something that diminishes and/or overshadows them reduces the amp into something else. And anything else then is just not the Marshall Major or even a Minor.
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Hey Max, welcome to the forum! It's nice to see another KT88 abuser holding the flag! Very nice chops!
I've seen the Union Jack 200 watt Major amps on fleabay. It looks like they do very nice work! That is pretty cool that they built one custom for you.
Per Ritchie's tech he ditched the HS live after Marshall did the OWM with the light bulb limiters around the Fireball album - although Ritchie still used the HS for recording, presumably at lower volumes. The MkIII was as you said adding the Aiwa push. Then his tech built a 12ax7 treble booster into his Major for the Rainbow days using the unused PA tube knockout. (See pic below)
Like you said, I am a huge fan of working these tubes hard and as I said many times in this thread, I think it is a large part of what makes this amp sound so fantastic and unique. However, as you probably know, it comes at a high dB cost. That was what was so great about Michaels video. I think he was able to capture some of that magic at a lower volume.
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max, thanks for the feedback and clips.
--pete
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Thank you so much guys, I'm glad you liked the tests. I'm surprised at how well it's holding up, I play it always at full volume with the treble booster and other than having to replace KT88 pairs every few months it doesn't even run too hot. I think I'm biasing the tubes at around 35mA or less.
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Hi guys, After mulling over the Holden Wasp schem things became strangely similar to the MAJOR. Because it had been modded and the original schematics were only traces of other models and a weird PI that had a tube between it and the power tubes.
When I finally was able to nut out the probable preamp, it then looked similar a Marshall pre, just some slight changes to component values that would not have altered the sound much.
The Ecaps need replacing so the PCBs need to be removed, this is not too difficult as there is only a few wires attached.
This got me thinking of other components that could be replaced to get some better MOJO as it has been said they are a little lacking in this department.
So finding that the circuit is very similar to the MAJOR it is now a guide for me to do some much needed tweaking.
I have not played it as there was some crackling happening and one of the power tube sockets was loose, also it has a fixed, fixed bias and the resistors had drifted a bit.
The tone stack was said to be a bit lifeless.
The PCB themselves are OK to look at, so to change the components will be easy, so if both channels of the MAJOR are a useable circuits I will change components to suit.
Again the PI and driver are on a PCB, this is different to the MAJOR with driver feeding the power tubes from the CATHODE :dontknow:
The 6550s I think are biased to 100w which I agree is tooo much watts for me. The PT and OT are huge,so its a bit of a waste to lower the output to 60-70 watts but this I think would run the 6550s a bit cooler.
To add a PPIMV would be great as well as a master vol (after TS) I did this on a JTM 60 and it worked very well.
OWM, looks to be a great feature and rather remove one channel, there is room for another preamp tube in the chassis. This would mean I may have to etch another PBC but that won't be a problem.
There is room on the front panel for a Master vol at the end of tone control/presence, PPIMV on the back and the OD between the volume and treble. This can be switched via a pull pot.
Angus liked them and now I can see why, so being not a exact copy I don't want it to be a"WANTA BE" but tweak it to be a better useable amp that "COULD BE" Thanks
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Good stuff!
Minor?
Jr?
Hey, what about ya start with SVT iron and build a Lt. Col.? :l2:
Sure, you'd have to stand about 10 miles a way to get the full on effect, but... :laugh:
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Timbo,
Man, thanks for sharing this! Your schematic looks great. IF you are OK with it, let's post the SCH schematic in the SCH Library of schematics under the Marshall Major thread. Feel free to add any comments about your design that you think would be useful.
http://el34world.com/Forum/index.php?topic=17556.0 (http://el34world.com/Forum/index.php?topic=17556.0)
Best regards, Tubenit
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You guys are good !!
You all basically figured out the circuit, here's a few picture I took of the board.
(http://i296.photobucket.com/albums/mm172/OdieMichaels/IMG_1250_zps72z2tiyr.jpg) (http://s296.photobucket.com/user/OdieMichaels/media/IMG_1250_zps72z2tiyr.jpg.html)
(http://i296.photobucket.com/albums/mm172/OdieMichaels/IMG_1245_zpsejrsgqgb.jpg) (http://s296.photobucket.com/user/OdieMichaels/media/IMG_1245_zpsejrsgqgb.jpg.html)
(http://i296.photobucket.com/albums/mm172/OdieMichaels/IMG_1237_zpsgo1zqdg4.jpg) (http://s296.photobucket.com/user/OdieMichaels/media/IMG_1237_zpsgo1zqdg4.jpg.html)
(http://i296.photobucket.com/albums/mm172/OdieMichaels/IMG_1239_zpseikdnhlx.jpg) (http://s296.photobucket.com/user/OdieMichaels/media/IMG_1239_zpseikdnhlx.jpg.html)
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Hi Guys. It's been a long time since I have even lurked. You guys are great. But I'm afraid I will catch the 'fever' as it is contagious.
In the proposed schematic: Major Marshall OWM & PPIMV. In the power rail, B+ segment, should there be a tie in the middle between the two 56K resistors and the two caps? If so, it is missing in the drawing.
Here is some lore as I understand it. When Richie started using the Major he was using a Gibson. After a conversation with Eric Clapton he gave the strat a try and never looked back. My point being that he found the amp first and changed everything else in his set up. So it must be something special to play through.
All amps are a compromise. I think the 30 watt version, with 2 KT88's and a lower B+, sounds like an ideal compromise. The problem has always been volume. If you look at the 1959 and the 1987 the major difference is two power tubes vs four power tubes. But the 1987 lacks that 'in your face' sound that the 1959 produces. A car anology would be small block vs big block. That is one of the trade offs selected. The other trade off is the lower voltage to the power tubes. A car anology would be a single carb vs dual carbs. So we know before one is built that it will not be the same, and how could it be at 30 watts vs 200? I am hopeful that it will capture the Major essence by matching the preamp at near original voltages and tapping the unique characteristics of the KT88 at lower voltages.
But if it doesn't do it for everyone on this board, it may require a higher watt version in the 60 to 80 watt range. My question is: if it has to have more output to get close enough, would it be better to go to four tubes at a lower voltage, or two tubes at a higher voltage? Four tubes would put the output at around 60 watts. The 1959 vs 1987 anology says more tubes at a lower voltage might come closer, but I am uncertain because both amps are running similar voltages into the power tubes. But we do know that the current flow to the OT is what is making the difference in the sound. A car anology would be: a big block with a single carb would deliver more torque off the line but may not reach top end as fast as a small block with dual carbs. Somehow, in my sorry little mind, I am equating more torque with the 'in your face' sound... cleaner low end punch due to a higher current flow. Or is it because with 2 tubes on each side of the push/pull the average flow is a more accurate or smoother reproduction of the original signal making it sound cleaner and punchier? Or is it because with two tubes on each side in parallel, the circuit impedance is halved yielding a cleaner reproduction? Is my car anology backwards or perhaps worthless for sorting this out? I know this is subjective, but I don't have enough build time to know from personal experience.
When it comes to volume, the standard application of an amplifier is to apply a small signal to a higher current flow in order to make the signal larger. Thus the standard power rail where each stage operates at a higher voltage than the stage before it. What would happen if a custom power rail was used such that it applied a higher voltage at B+ than it did at A+? The power tubes move a higher current by design but if the voltage is lower it would equate to a lower current at the OT without altering anything else in the original design. Would the power tube still operate correctly or fry the grids?
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Great analogy. I actually tried my Major with two tubes and it sounded different. Talking with Ritchie's amp tech I was extremely lucky I didn't let out the magic smoke when i did that. But again, talking to him I was extremely lucky doing all the things I did to this amp over the years to get that tone at a lower volume. Yes Ritchie started out with the Gibson running through a hornbey skewes treble booster (half of the Zonk Machine). Then the strat. Then the factory master volume that was finally on pipe by machine head. Ritchie was in the factory tweaking for almost a year.
I don't know which way to go for tube quantity because we have made some concessions to the design anyway. I can tell you the Park 75 was an awesome sounding amp with the kt88s!
Jim
Ps good to see you back!
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My opinion is the appropriate higher voltage on two tubes will definitely make them sing properly and also give them the proper headroom and break-up characteristics you're looking for to get that in your face / torque going. Less power on the power tubes makes them "softer" and the grids more sensitive to being hit so they give it up much easier (why I say softer) with the same amount of signal. The only sure way to find this out is lower your power tubes' B+ artificially using your temporary favorite method of choice. But also know that it will have an affect on your OT's reflected impedance too. Not like it should do any damage of any kind - just that it will cause a performance difference here too once lowered to a certain point. Your primary impedance should lessen as voltage lowers so you could be better off simply plugging your 8ohm speaker into your 16ohm setting/output jack to get the magic back?
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CORRECTION:After looking at the guts photos provided by Michael R/T (thanks!), I see a problem with the circuit as drawn. On the V2 triode after the tone stack the 1M resistor ties across the triode tail to ground between the 2.7k resistor and the 100k. It does not just go directly to the .047 cap to V3. You can see this connection to the right of the last orange cap to the right in the photos. That last orange cap on the right is the .02 cap from the treble center wiper (you can see the pink wire connecting the cap to the pot), which is the input to the V2 triode. Someone else brought this up earlier, was it Pete? There was some discussion as to why that triode tail had a 2.7k and a 100k in series to ground. This is why. The old schematics did not have this connection drawn in, (seems like some showed this as a jump-over instead of a connection point) but the pictures tell all. EDIT: Never mind... I see that this has been corrected since I downloaded the schematic.
EDIT: I also see that he has a wire jumpering the output from the first channel into the second channel (large white wire from the volume out on the pot to the input of the next channel). This is similar to the one wire mod except you retain the clean output from the first channel. With the OWM as drawn you only have the output from the second channel going through. This may actually be a better approach. The input to the second channel would also see two 68K resistors in parallel to ground from the channel's input jacks. This would keep the signal from the first channel from overloading the second channel too much and get a better overdrive from the second channel. Which channel is the bright channel, Volume I (second from the jacks) or Volume II (right next to the jacks)? It looks to me that he is plugging into the normal channel (II) and using the bright channel (I) for overdrive with the one wire mod. If so, that is the opposite of the new circuit as drawn. Or do I have my bright and normal channels reversed?
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I'm putting the pre amp section in cascade (series)
Gain factor is multiplied when in series instead of in parallel (as it is normally know, stock).
I plug my guitar into channel II then turn Channel I and Channel II volume to 10, then keep the Master Volume (PPIMV) low to control the overall volume.
I get a good amount of gain and crunch this way. Now to add extra gain and crunch I use a 1/4 male jack only with no cable attached to it.....
I take this plug and stick it into channel 1 jack (high or low) to get even more of a blast in gain. :-)
https://www.youtube.com/watch?v=_ZBWayUpmpc (https://www.youtube.com/watch?v=_ZBWayUpmpc)
https://www.youtube.com/watch?v=tQp52C10Wvs (https://www.youtube.com/watch?v=tQp52C10Wvs)
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Michael,
With the assumption that the components on the turret board follow in order in the preamp section, then Channel II is the normal channel. That is the one you are plugging in to. That channel output is cascaded into the treble channel (Channel I) for the cranking overdrive. This is the opposite order of channels from the new circuit schematic with the one wire mod built in.
It makes sense that the components would follow in order to avoid confusion and errors during assembly. Starting from the end of the chassis, the first input jacks are Channel II, the first components on the turret board are Channel II and it goes to the first triode (pins 1,2,3) of V1, this is the normal channel. The second input jacks are Channel I and the second group of components on the turret board are Channel I and it goes to the second triode (pins 6,7,8) on V1, this is the treble channel. Based on this logic the preamp circuits need to be swapped in the new design to achieve a sound similar to yours.
The input jacks in the marshalls have shorting contacts in them. When nothing is plugged in the input is shorted to ground through the chassis. This keeps the channel input quiet. When you insert a plug it lifts that contact. So when nothing is plugged into channel I with the one wire mod the channel input sees the signal through a 68K resistor to ground. This will lower the input signal slightly. When you plug in the dummy plug the input now sees the 1M resistor to ground letting all of the input signal reach the tube.
The other difference is that your one wire mod takes the signal directly from the volume wiper and inserts it directly into the next channel tube, bypassing the 68K resistor. In the new circuit the signal is tapped after the 470K mixing resistor following the volume control. This will reduce the signal and cause some loss of treble compared to yours. This may not be a significant point, but it is a difference.
Another thing I noticed is the preamp in the Major is really hot. For example:The voltage at pin 1 of V1 is 190v. In the 1959 it is 150v, and in the 1987 it is 100v. This is a heck of a difference in how hard the preamp is being pushed before the tone stack. No doubt this is a contributing factor in its sound.
Question: Does it really make no difference whether you insert the dummy plug into the low or high jack on channel I? The reason I ask is that the typical wiring representation of the marshall input jacks show a different circuit and only plugging into the high signal input will enable the 1M resistor to ground. Inserting a dummy plug into the other jack should make little difference.
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Alice,
If I am not mistaken, Michael's is a 1978 Bass model so no treble channel. The schematic that was drawn up referenced a Lead model.
Jim
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I checked a bass schematic. It's a Marshall Major but its designation is 1978. The tails to ground for both channels bridge together and go to a single pair of 820R/250uf. The output cap is .02 for channel II and .002 for channel I same as the lead model. The only difference between channels is the output cap, with channel I being brighter. The remainder of the circuit is identical to the lead. I guess it would be OK to leave things as they are. If it doesn't sound the same it would be a simple mod to match the bass circuit. At least with the design as is, you still have the lead channel I with the OWM turned off.
I was just trying to be sure it was right. You can't do things differently and expect the same result. If you are trying to get Michael's sound, this design has differences in the preamp. But that isn't the core objective of this design.
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I checked a bass schematic. It's a Marshall Major but its designation is 1978. The tails to ground for both channels bridge together and go to a single pair of 820R/250uf. The output cap is .02 for channel II and .002 for channel I same as the lead model. The only difference between channels is the output cap, with channel I being brighter. The remainder of the circuit is identical to the lead. I guess it would be OK to leave things as they are. If it doesn't sound the same it would be a simple mod to match the bass circuit. At least with the design as is, you still have the lead channel I with the OWM turned off.
I was just trying to be sure it was right. You can't do things differently and expect the same result. If you are trying to get Michael's sound, this design has differences in the preamp. But that isn't the core objective of this design.
Some additional lore... I have heard examples of the OWM on a Major lead version with the lead channel (channel 1) into channel 2....AND visa versa... Some sound good but different, others sounded like mushy blatty crap. The lead channel on the lead version has a "top boost" type circuit and it is VERY hot. Ritchie's amps before the Marshall OWM were Lead versions. His amps after the OWM were all Bass amps - but with some treble added. This is when he spent time at the factory blasting the poor women and tweaking the mod. The details of this mod are lost to the Marshall employees who performed the work and his amp tech who removed it all, and who is not talking. His amp tech did a few mods to make the amp more stable but took it back to it's original design, made sure they had the custom wound OP replacement trannies, then added his built in treble booster for the Rainbow years and beyond. Ritchie's amp tech is who figured out for Marshall why the Majors were blowing up on an alarming basis. Marshall did not have a clue as it was designed by GEC, and GEC could not figure it out either. He was fixing Ritchie's amps every few days and he used to work for McIntosh so he had a pretty solid background!
Jim
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Here is a mod. Take a SPDT switch and connect pin 8 of V1 to the middle contact. Connect the 2.7k/.68uf to one side, this is the 1967 model. Connect the other contact to pin 3 of V1, this is the 1978 model. The lead amp has two 500pf caps that make channel 1 brighter by jumping the treble over the channel volume control and channel mixing resistor, but other than that they are the same. Now you can switch between the models.
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As you can see, there are some differences between the old plexi version and the one from 1973 that I have (besides being a lead version). These are some old pics that I took when I first got it. Notice the old doorknob resistors. Also notice the additional double insulation on the B+ runs to try and reduce the 1800v flyback arcing. Also pointing at what needs to be on 8+ to reach nirvana..... :m15
Jim
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current and corrected schematics in .SCH format can be found in the link below:
http://el34world.com/Forum/index.php?topic=17556.0 (http://el34world.com/Forum/index.php?topic=17556.0)
thanks jazbo8 for the errata. :-)
PDF version attached to this message.
Major_Major is 200 Watt Fixed Bias
Major_Minor is 100 Watt Fixed Bias
Major_Minor_III is 50 Watt Cathode Bias.
--pete
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FusionBear (who posts on TAG and the GearPage) is building a "Major Minor":
http://www.thegearpage.net/board/index.php?threads/the-marshall-major-and-a-tribute-mini-build.1750906/ (http://www.thegearpage.net/board/index.php?threads/the-marshall-major-and-a-tribute-mini-build.1750906/)
I've seen his previous builds and videos and they are pretty impressive. It will be interesting to follow this thread and see what he comes up with? He also is a great player.
Just thought you guys might want to know. I think he is using a "mirror image" of a layout pretty similar to what we have come up with for this project.
With respect, Tubenit
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Just saw your post with the link. Wow! That is a beautiful build! Looking forward to the sound clips!
Jim
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! No longer available (http://www.youtube.com/watch?v=aBADx0TlrCI#)
Well, FusionBear got the Major Minor built! Sounds pretty good to me.
The thread is here on the Gear Page:
http://www.thegearpage.net/board/index.php?threads/the-marshall-major-and-a-tribute-mini-build.1750906/page-4 (http://www.thegearpage.net/board/index.php?threads/the-marshall-major-and-a-tribute-mini-build.1750906/page-4)
It's fixed bias with 50k pot I opted for a PT that is 390-0-390 @ 300mA OT is 120 watt @ 4.3k primary Ultra linear
With respect, Tubenit
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Listened to it with headphones and it kind-of has that full bodied KT88 UL ballsy sound. However, I think he has gone too far away from the Major tone. He did say he was looking for, and tweaking for, the Van Halen 1 tone so he has admitted that was his goal. There is also that high end squealish edge that I'm not real keen on....and that was with a humbucker. The Major on pipe has a nice smooth ringing high end, not unpleasant. I guess what I don't understand is why? He could have built a 50 or 100 watt EL34 plexi style amp to nail the Van Halen tone, so why go through all the trouble with a Major design and then move away from it? The Major has such a unique sound, I don't know, I'm kind of disappointed. But hey, that was a beautiful build and if that's what he wanted, more power to him.
Jim
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If anybody decides to build a low watt (30-40 watts) cathode biased major... please give us feedback ASAP. THX joe
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B
If anybody decides to build a low watt (30-40 watts) cathode biased major... please give us feedback ASAP. THX joe
Building one now.I don't know if it is exactly what you are looking for as i won't be using an ultralinear output transformer.
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Sounds good....I probably wouldn't either. Please keep us posted. thx, joe
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quote i received June 1, 2017 from heyboer for marshall major iron - in case you're interested...
On the PT , HTS-5725 Original wind 0-110-120-200-225-245 primary with M-6 core steel for 50/60 Hz laydown mount 1 3/4 EI X 2 1/2 " stack
1 pc $265
2 pcs $250
HTS-5725-1 is a dual 120v primary. hook parallel for 120 , series for 240 is M-50 core steel for 60 Hz laydown , same as above
1pc $225
2pc $210
HTS-5402 200 watt OT original wind , has 2 primary sections and 5 secondary sections. these are hooked series or parallel to get different speaker loads
M-6 grain oriented core steel. Stand up mount ,1 3/4 EI X 2 1/2 " stack
1pc $250
2pc $235
--pete
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Pete,
Are you building?
Jim :icon_biggrin:
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Pete,
Are you building?
Jim :icon_biggrin:
possibly: if the hayboer OT offering isn't a copy of the flawed OT.
--pete
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The original used a single layer of very thin masking tape between windings. I think the mylar will work just a little bit better! I do know a few owners who used Heyborer for repairs and never had a problem. Also know a few who used it on new builds. Never heard a complaint. Different preamp? Noooooooo!!!!! :sad2:
Jim :icon_biggrin:
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Different preamp? Noooooooo!!!!! :sad2:
Jim :icon_biggrin:
i guess i shouldn't be telling you that the player who wants the different preamp will be playing a tele through it too... :icon_biggrin:
oh, wait, just did! doh! :BangHead:
--pete
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I don't know you......
Jim :offtheair:
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I don't know you......
Jim :offtheair:
yes, yes you do... i'm the forum idiot that won't follow convention, :icon_biggrin:
mine will be the major amp in all it's glory, the other will be a spin of it with an added spring reverb.
see, all is not lost. have faith in this wiley texas hacker... :occasion14:
--pete
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i'm the forum idiot that won't follow convention
+1
You can buy convention of the shelf, creativity and craftsmanship comes special order :icon_biggrin:
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! No longer available (http://www.youtube.com/watch?v=aBADx0TlrCI#)
Well, FusionBear got the Major Minor built! Sounds pretty good to me.
The thread is here on the Gear Page:
http://www.thegearpage.net/board/index.php?threads/the-marshall-major-and-a-tribute-mini-build.1750906/page-4 (http://www.thegearpage.net/board/index.php?threads/the-marshall-major-and-a-tribute-mini-build.1750906/page-4)
It's fixed bias with 50k pot I opted for a PT that is 390-0-390 @ 300mA OT is 120 watt @ 4.3k primary Ultra linear
With respect, Tubenit
@Tubenit Is there a layout for the major MINOR III ? The TAG links are no longer available ☹️
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I am not aware of one specifically. However, reply #4 on this thread is a layout for a Marshall Major and it is editable. You might consider reworking it looking at the Major Minor III which also has a schematic on that same thread.
http://el34world.com/Forum/index.php?topic=17556.0
The other thing to consider IF a previous layout has disappeared is using the "Wayback Machine" internet search?
With respect, Tubenit
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No no, all of the forum's links work, but unfortunately I am on my phone for a few days now and cannot open .sch files obviously. I'll check the 100w version of the layout if you say it's there, and give a try to turn it into the 50w minor iii
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A while back I drew up a Major schematic by looking at the gut shots from four different Major's. One thing I was unable to de-tangle was the large number of wires coming out of the OT and going to those two little exterior circuit boards. Anybody got any insight into that?
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That's what Dawk called the "Christmas tree" - not sure why? It is just a connection between the OPT and the selector switch (button). I actually think it allowed the "girls" who assembled the amp to make those connections without flipping the amp. Ritchie's amps were wired direct 8ohms, bypassing the "tree". He was not a fan of the silly pull out ohm selector button.
Jim
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That's what Dawk called the "Christmas tree" - not sure why? It is just a connection between the OPT and the selector switch (button). I actually think it allowed the "girls" who assembled the amp to make those connections without flipping the amp.
I've counted no fewer than nine leads going to the Christmas tree. This reminds me of Hammond's 1600 series where secondary coils are connected externally to get the various impedances.
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Actually there are 13 connections! Dawk said Ken Brawn told him the women could make (4) 50 watt or (2) 100 watt in the time it would take to build one Major. Only ~1200 were built (per internut lore...) but I was told less than 1000 of the Major. There was the Pig (less than 50) and the "200" (less than 30). With the low volume (so to speak!) of production for the Major, no fancy assembly jigs were ever built. The women needed help flipping the chassis over after the tranny's were installed (~80 lbs.). I think the Christmas tree was a cheap workaround to speed production.
Jim
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or older sowter transformers with the 4 x 1Ω windings.
--pete
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Oh its a single circuit board with a circuit board "cap" to cover the exposed soldered connections. If the gold expanded metal vent screen gets pushed down it can lay on top of this. Don't ask me how I know....
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Actually there are 13 connections!
Nine coming from the OT and four going to the impedance selector for a total of 13?
Thanks for the picture. I'll add it to my collection.
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I am not aware of one specifically. However, reply #4 on this thread is a layout for a Marshall Major and it is editable. You might consider reworking it looking at the Major Minor III which also has a schematic on that same thread.
http://el34world.com/Forum/index.php?topic=17556.0
The other thing to consider IF a previous layout has disappeared is using the "Wayback Machine" internet search?
With respect, Tubenit
Are all caps rated @ 600v, except for the 500v filters? I may try my luck with the minor iii :m20
Resistors 1/2w ?
And also.. is the minor iii above 50w or something?
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If the Major Minor III is the one Pete (Dummyload) drew up, I don't think he was running those voltages. I don't have the sch program on this computer so I cant look at it. If I remember he had figured about 50 watts for that version? Maybe he can chime in. He and Ed have built numerous KT88 projects. Don't be afraid to ask questions. We beat this amp up pretty good in this thread, that was really neat getting everyone's input. However, I don't think anyone ever built one! (except for someone on another forum who ripped off Tubenit's design and called it his own...) So, you can be the hero of this 5 year old thread!
Jim
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http://el34world.com/Forum/index.php?topic=17548.150
EDIT (reply 187)
I don't have the sch program on this computer
the 3rd file down is PDF, but I know, after two, things get a little fuzzy :icon_biggrin:
IMHO there are 3 too many input jacks :laugh:
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If the Major Minor III is the one Pete (Dummyload) drew up, I don't think he was running those voltages. I don't have the sch program on this computer so I cant look at it. If I remember he had figured about 50 watts for that version? Maybe he can chime in. He and Ed have built numerous KT88 projects. Don't be afraid to ask questions. We beat this amp up pretty good in this thread, that was really neat getting everyone's input. However, I don't think anyone ever built one! (except for someone on another forum who ripped off Tubenit's design and called it his own...) So, you can be the hero of this 5 year old thread!
Jim
Oh yes.. I AM building this! By the way, that other guy from the ampgarage forum built the 100w, not the mini iii which is indeed 50w cathode bias. I'm on my phone the past few days and cannot open sch files either. The pdf doesn't state resistors' wattage (apart from the obvious 1kw's) or cap voltage..
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If it's mine
ALL plate R's are 1w, all other R's (beside important big PA ones) are 1/2w
all coupling caps are 400-600vdc
all PS caps with + sign need to be bigger than the vdc they deal with
all odd caps in-circuit with + signs can be guessed at pretty easy
bigger is better :icon_biggrin:
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EDIT (reply 187)
I didn't get very far with reply #187, but I scrolled on down to reply #194 by Dummyload. Here he talks about a Heyboer replacement OT for a Major with five secondary sections. I can see nine leads coming out of the secondary side of an original Major OT and there could easily be a tenth that I can't see. Or it may have an internal connection so that it has five sections but only nine wires.
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bigger is better :icon_biggrin:
... that's what she said! ... and I agree xD
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with reply #187
:laugh:
it's actually #184 where the pdf is, but I'm dyslexic so the "4" got replaced by the "7"
from the thread title :think1:
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IMHO there are 3 too many input jacks :laugh:
My dear baaay, THAAAT is wot is knawn as trrradition!
Jim :icon_biggrin:
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That's what Dawk called the "Christmas tree" - not sure why? It is just a connection between the OPT and the selector switch (button). I actually think it allowed the "girls" who assembled the amp to make those connections without flipping the amp.
I've counted no fewer than nine leads going to the Christmas tree. This reminds me of Hammond's 1600 series where secondary coils are connected externally to get the various impedances.
based on the heyboer major clone transformer information i posted in 2017 (reply #192 (http://el34world.com/Forum/index.php?topic=17548.msg234365#msg234365)), the OT is stated to have 5 secondaries & two primary sections - so one would assume there would be AT LEAST 10 wires to the "x-mas tree".
--pete
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it's actually #184 where the pdf is, but I'm dyslexic so the "4" got replaced by the "7"
Maybe not. I said reply #194 and now it's reply #192. Of course, I could be dyslexic, also. Reply #160 is still reply #160.
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Ok, dont laugh.... too hard....
I've been here for what....15? 20? years? On this board I have posted over 3000 (mostly useless) times. On these long threads I see people referencing reply #200 or posting #100 and I'm thinking, who the hell has time to count these posts!!!! Get a life man!!!!
sigh....
I just NOW noticed the reply count... :help:
Oh jeez, I just need to dig the hole now, fall in, and wait for the inevitable.
Jim :sad2:
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Ha! Talking about dyslexia! I've mentioned about having a hard time turning layouts into schematics and vice versa!!! Takes me x4 times longer than the average person! But if as you said the major minor and the minor iii schematics are 101% correct and accurate, it's way more than worth the time dedicating on a layout and complete build!
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one of the fun things in the Navy was the "telephone game", by the time the phrase came back around I was married to my Mom :cussing:
I just seem Minor III pdf n went with it n messed up :think1:
SMG
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Re: Marshall Major 1967
« Reply #184 on: January 08, 2015, 04:50:12 pm »
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current and corrected schematics in .SCH format can be found in the link below:
http://el34world.com/Forum/index.php?topic=17556.0
thanks jazbo8 for the errata. :-)
PDF version attached to this message.
Major_Major is 200 Watt Fixed Bias
Major_Minor is 100 Watt Fixed Bias
Major_Minor_III is 50 Watt Cathode Bias.
--pete
* Major_Major_Schema.pdf (58.68 kB - downloaded 201 times.)
* Major_Minor_Schema.pdf (56.15 kB - downloaded 242 times.)
* Major_Minor_III_Schema.pdf (52.2 kB - downloaded 240 times.)
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> dyslexia! ...hard time turning layouts into schematics and vice versa!!! Takes me x4 times longer than the average person!
The "average person", my neighbor, your neighbor, could never do that. Jimmi next door is a good mechanic but can't draw the fuel gauge of a Hudson (2 wires!). So you are already in the 1%.