Marshall Major 1967

[Ed_Chambley]

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. 

[sluckey]

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.

[terminalgs]

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

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.

[Ed_Chambley]

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.

[Ritchie200]

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

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'

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

[tubenit]

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

[Ritchie200]

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

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?

Jim

[sluckey]

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.

[Ritchie200]

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)!

Jim

[tubenit]

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. 

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.

 

And no, we have a policy to not pay ransoms to kidnapped forum members.  Sorry!   

With respect,  Tubenit

[sluckey]

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.

[Ed_Chambley]

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.

[Ritchie200]

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.... KT88

[DummyLoad]

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

[DummyLoad]

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

[sluckey]

the major minor jr.

How 'bout Maj. PeeWee Marshall?

[jojokeo]

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? 

[DummyLoad]

the major minor jr.

How 'bout Maj. PeeWee Marshall?

that'll do! :-) 


--pete

[tubenit]

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

[jojokeo]

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.

[jojokeo]

something I just found backing up Jimbo's claims on this beast from a puplication by Don Hunter

[tubenit]

I am thinking that "the" Major Marshall tone may be unobtainian at less then 80-100 watts?   

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

And this suggests cathode biased around 400v with ultra-linear would be around 30 watts
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.
 

With respect, Tubenit

[jojokeo]

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?

[tubenit]

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 

[SILVERGUN]

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
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.  .

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     
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.
 
You're welcome.

[Ritchie200]

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

[Ritchie200]

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

[tubenit]

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

Edcor has a 275-0-275 PT with 325ma that would work just fine and is reasonably priced:
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

[SILVERGUN]

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   
 

SG!!!  Well said young man!  Thank you!

[jojokeo]

SG!!!  Well said young man!  Thank you!

This thread is having an affect on Jimbo like going to church, confession, or something??? 
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?

[SILVERGUN]

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.

[jazbo8]

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.

[tubenit]

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

And there is also this Edcor that could work with the Edcor PT:
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

[sluckey]

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.

[jojokeo]

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?

[DummyLoad]

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

[jazbo8]

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.

[tubenit]

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

[DummyLoad]

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.

[Ritchie200]

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

[jazbo8]

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.

[tubenit]

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

[SILVERGUN]

I agree with everyone,,,,even Jim   

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.

[jazbo8]

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.  

[tubenit]

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

[jazbo8]

So who's going to build one first?   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 for example, so your 30W version might just be taking the idea to a new direction afterall.


Audio Amp Co.'s RBMM:

[Ed_Chambley]

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.


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.

[tubenit]

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 

[Ed_Chambley]

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


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!!

[Ritchie200]

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]

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)

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