Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: tubenit on July 27, 2012, 06:02:07 am
-
Been thinking about another amp idea ............. & drew this up based on some different things I've tried that "might" work together as a great amp.
Sort of a Marshall-ish clean into sort of a Dumblish OD ......... add an active FX loop (which also works as another OD boost at some level) into a D-style LTPI. I used this FX loop in the reverb/FX unit that I built some time ago.
I'm wondering if using the recovery on the FX loop will work well as a Master Volume. I'm thinking it might?
Just thought I'd share the idea. CHECK for errors!
With respect, Tubenit
-
Hey Tubenit, Looks to be another great amp. As for the active FX, it looks similar to the boogie FX and as you can see there is three switches. In the bunch of schems in Dougs library for boogie, there was a cheat sheet that gave the sequence for the LDRs but it did not include the FX loop.I can't think what the idea is behind the three switches but i sure that the jacks can be switched out to turn the FX into a slight boost similar to your drawing. Good luck. :icon_biggrin:
-
Looks promising Tubenit.
-
OK, I built this today! Nice amp. Very harmonically rich clean and OD tone.
Downside, it lost some blooming and quite a bit of the "vowel" tone that the TOS 2CF had.
Having said that, the harmonics with the tone stack following the CF are really the nicest I've been able to come up with for any amp I've built. The amp has a really super sweet musical tone. I do like this amp for chording more. Whether on clean or OD, the individual notes really shine thru. I think playing really fast lead riffs would cut thru quite well with this amp.
I think it sounds more Marshallish on the clean & with the OD on .......... it is sort of a blend of the Marshallish and Dumblish tone.
The amp has almost about the same sustain as the TOS 2CF, but the notes don't swell and bloom the same for some reason?
The midboost on this version creates a MUCH more dramatic tone change then the TOS 2CF midboost did. The volume is more increased and the overdrive is definitely overdriven a bunch more. Not sure why?
Because of how clean/clear the notes are ............ I think this could be a good choice for a lower wattage "Eric Johnson-ish" tone? And if you can play riffs super clean and super fast, I think the amp would meet that need also. It is very articulate in that regard.
IF you prefer the Larry Carlton and Robben Ford tone (at low volumes), then the TOS 2CF would be a better choice. I think the TOS 2Cf is a better blues amp also.
Just thought I'd share the results!
With respect, Tubenit
-
Cool,
Man that was fast Tubenit, I like how go from thought to, ok here it is.
Bill
-
OK, I opened the amp back up and worked on tweaking it some more. Nothing was needed for the clean channel. It's really super nice with great harmonics using the Marshallish topology with the cathode follower tone stack.
I tried ALOT of different tweaks on the OD channel to add some warmth and blooming back in. Using alligator clipped wires and small caps I tried lots of stuff and did NOT use hardly any of them. Most attempts added grit or even oscillation.
BUT I did find two things that worked fantastic. 1) removed the network of resistors and caps between the DPDT relay and the trim pot. That opened the amp up and made it more touch sensitive and increased the gain somewhat. 2) Changed the 1uf on the 5879 cathode to 1.68uf that hit a really nice sweet spot for the gain. Very smooth and rich with harmonics.
IF prior to the mods, the TOS 2CF was a 9.5 on my "blooming feature" scale where the notes sort of open up and bloom as they sustain, then I am now at a "8.5-9" on the blooming with these mods. And I got back almost all the vowel tone now (which I like).
What has also remained is the harmonics are much richer with this amp then the TOS 2CF. It's just really musically sweet in the tone.
So it's a trade off, this has better harmonics ......... better clean tone and is more versatile. I can get really close even to the chimey HoSo56 amp tone by dialing the tone and volume pots just right. BUT it still has the Dumblish OD tone when I need it.
With respect, Tubenit
-
Observation about the gain stage cathode caps prior to the cathode follower. The cathode caps on that stage seem to really make a BIG difference in finding a sweet tone, IMO. For example, this amp uses a 1.68uf on both the clean and OD cathode cap (gain stage prior to CF).
I find 1uf too thin. I find 2.2uf to have too much grind and not enough sweetness. I tried a 2uf also, but it lost some sweetness compared to the 1.68uf for some reason?
In other words, this seems to be a very sensitive area for component values. Very small changes make some significant differences in tone, IMO.
With respect, Tubenit
-
Very nice, T!
I have a redundant amp that would be fairly easy to convert.
I haven't built anything in quite a while,so I think this would be an easy way to get back in the swing!
Thanks for you work & sharing!
G
-
This is proving to be a really sweet amp! The pot controls are definitely more sensitive and responsive. This is especially true for the tone stack. I can mid scoop it or add a significant amount of mids into the tone. Both bass and treble really dramatically change the tones. I can get almost a Marshallish harmonics and crunch but that is a cleaner tone that I more normally think of for a Twin Reverb. (I realize that is a terrible analogy, but it's kind of hard to describe)
The most interesting aspect of this amp is that I can dial the OD controls to keep the amp relatively clean but the OD stuff adds lots of harmonics and increases the sustain even though the tone is still clean and clear. In other words, (I can dial the OD controls where) it goes from clean to clean with more harmonics and sustain without much of an overdriven tone.
At the same time, if I crank the mids up & engage the midboost, then I can get the blooming effect and more of the vowel tone. However, this is not as smooth of an OD vowel tone as the TOS was. It has a little more grind to it.
I think it might work to keep the OD in the circuit all the time and use the midboost for the lead. I think I'd almost like to have a relay switch that engages the mid boost and increases the mid pot setting at the same time & dropping some higher frequencies to boot. I may ponder that and see if I can draw up an idea to make that happen?
I don't know if I like this amp as well as the TOS, but it sure seems to have a unique tone to it. I definitely think the way this is voiced would cut thru a band mix quite well?
The amp takes pedals remarkably well also. More later ...................
with respect, Tubenit
-
You aren't wasting any time on this one & I'm liking the way this one seems to be shaping up T. It has attributes that I'd like to have the way things are going right now, and I'm liking the pentode location too. What tube are you using/liking in the pi stage, 12aT or aU?
-
So far, I have only tried a 12AX7 in the LTPI, but I plan to try a 12AT7. To be honest, I have been surprised that the clean tone is so clean using a 12AX7 instead of a 12AT7.
I like the clean (no changes needed, IMO). I like the OD set on cleanish tone with harmonics and sustain. I need to work on the vowel/blooming tone to get it smoother. I've written down 6 different ideas to try & will report the results back probably this coming wkend.
I mentioned it in an earlier post, but another surprise with the amp is how well it articulates the notes playing quickly. Just like a compression pedal seems to allow more definition of notes in fast riffs ......... this does the same but without the compressed feel.
With respect, Tubenit
-
Again, all very nice to see and hear back on with your results. Your efforts are much appreciated and anticipated as always. You have a good sense of things to try and a good way of interpreting what you're feeling and hearing and putting it into descriptions.
I don't think you'll have too much difference btwn the ax & at in the pi but there will be some ofcourse.
Lately I'm very much into qualities regarding sustain, note definition, harmoics, and sweet musicallity of tone and transparency which accompanies these characteristics. Then a little hair mixed into the notes blending a bit of pentode magic in there sounds real good if wanted.
If I may make a suggestion? I've built several amps biasing multiple stages at the same time btwn values typcially associated with Fender & Marshall. Fender's definitely give more overall gain, vol, & low end with everything else being the same. As you've seen in your sweet spot w/ the cathode/bypass caps - maybe try using more of Fender's in a few places and see if this may help open things up in a few areas too? I'm really curious what effect it may have - hopefully for the better in helping you get where you're trying to go?
Almost forgot - try taking a B1K pot wired across that 680r and instead use a slightly higher cap, maybe to 2uF - 5uF from wiper to ground. Then you'll have a variable gain/variable bypass cap going. I always like do this on my pentodes. You'll find different settings for different volumes making it very practical.
-
try taking a B1K pot wired across that 680r and instead use a slightly higher cap, maybe to 2uF - 5uF from wiper to ground. Then you'll have a variable gain/variable bypass cap going. I always like do this on my pentodes
IF I am understanding you, this is a variation similar to what KOC did on his Soma 18w amp with his "treble pot" which actually increased gain as well as adjusted treble. Not a bad idea. I may try that. I used this same idea on my very 1st amp design the Carolina Blues Special yrs ago.
With respect, Tubenit
-
I find it works really well and that whatever pentode (EF86, 5879, 6AK5, etc.) I use it on, the amp benefits from it depending on overall volume, gain, and your mood of the day. You version is basically the same as how I draw it up below.
-
OK, I had a few hrs to work on the amp this morning. Initial impression now after about 30 min of playing is I have it realllllly close to what I am wanting. I need to take some time and play it with the digital delay pedal in the passive FX loop. I find the digital delay will expose any high end hash or grind that I don't like.
Once again, I have found the right smoothing cap combination to increase blooming & not dampen it. I am still of the opinion that at times oscillation can stifle the notes sustain and blooming & that removing the oscillation with the right smoothing cap can increase the sustain and blooming.
I have been successful at continuing to improve the sustain and blooming. Still now quite as good as the original TOS or TOS 2CF but pretty close to it (maybe 93+% there). This definitely has much better harmonics, much better note definition and articulation & is waaayy better for playing fast cleanly done riffs. Closer to Mark Knopler or Eric Johnson style "tone" than someone like Gary Moore or Robin Trower or even Robben Ford.
I am really liking playing this amp! Very fun to play.
I will give a further "test" sometime in the next few days and repost my final thoughts.
With respect, Tubenit
I found the 68k in the tone stack to NOT be the ideal combination even though I was happy with it ......... UNTIL I tried the more Marshally 34k resistor there. Tightened up the bass notes in a good way. I also removed some paralleled coupling caps in the OD gain stages and added more smoothing caps & some of the architechture (back into the circuit) that goes into the trim pot.
I also tried jojokeo's suggestion of using more towards Fender values on cathode caps. I know I don't care for 22uf cathode caps, but I did try larger values. So, I tried 10uf on V1a and really liked it alot on the clean but not as much when the OD was engaged. I tried 6.8uf on the V2a (1st OD gain stage) & again it sounded excellent but I prefered the somewhat "softer & smoother" OD of the 4.4uf cathode cap.
-
T, just to confirm, are you finding certain cap values being associated with more/less subtle oscillations affecting the sustain which would mean these are frequency dependant? If so, I'm curious which one(s) seem to be affecting this and being the most sensitive to the issue? Thanks for trying the other values - helps to confirm or validate a few things.
-
are you finding certain cap values being associated with more/less subtle oscillations affecting the sustain which would mean these are frequency dependant?
Yes, that is my conclusion.
Kind of hard to describe, but it would be like the notes in the very high end have kind of a "hash" (using Geezer's term). It's almost like it has some harmonics that are a slight tad off key or something on certain notes. I am also thinking the upper mid's can have oscillation at times also? Maybe Geezer can voice his observations about that also?
So whenever this type of subtle oscillation is stopped, it audible seems to turn the note into a purer more musical sustain that is smoother.
When I first started building & quasi designing amps, I tried the traditional "snubbing caps" across the LTPI plates and also from plate to cathode on power tubes. Both of those dramatically muffled the tone like a blanket over a speaker. I still view those specific approachs as tone killers, IMO.
I think that negative experience left me (for a long time) viewing smoothing caps as a deterrant to good tone that should only be used as a last resort "bandaid" to a unresolvable problem. Now on the D-inspired amps, I view it as a positive tool that is intregal to shape the tone that I am looking for. Done right, it seems to open up the amp making it more musical, more articulate and with smoother sustain and tone. Anyway, that's my opinion.
With respect, Tubenit
-
I think you're experiencing "normal" shelving effects from the partially bypassing techniques determined by cap values used? So it seems you're right on with your thinking based on your findings and testing. With layout, lead dress, and other things out of the equation, the solution might just be corrected possibly being the way a single stage is being bypassed? Could be another way for using the "variable bypassing cap" as suggested earlier as a troubleshooting aide? Wire up one or two and simply clip them in after removing the originals. You can also see these affects in Merlin's biasing program and sub values of various components to see the affects there too which could help with the process. I don't know if you've used this before or not?
I agee with your last paragraphs and have re-assessed my prior neg tone ideas regarding smoothing or snubbing caps if done carefully. I originally resisted those ideas and techniques as you may remember some of the comments made in the past? I guess it just took me a little longer to warm up to things? :)
The schematic does have a lot of not only plate load caps but also plate to cathode caps, is it necessary to use both at the same time? I also see bright caps on large value gain/vol controls and also many voltage dividers mixed in. Have you thought about using split load resistors instead to help lessen the need voltage dividers and then bright caps on some of those? Also maybe try lowering vol/gain pot values to 100k, 250k, or even 500k, then the bright caps wouldn't be needed? This would also place more of a load on prior stage thereby reducing gain to help eliminate the need for voltage dividers here also. This alone could easily eliminate that gain-induced high end hash?
Lastly, are the osciallations coming only when the OD channel is in use?
Just throwing something our there to maybe also try? I had an amp that had an oscillation issue on a MV control when it had a bright cap on it, and went away w/out it but the amp NEEDED it since it wasn't ran wide open very often. The osciallation was most noticeable on a setting of "7 to 8". I ended up using a 47k in series w/ a 470p and this got rid of it and restored the brightness that was needed. Crazy but worked.
-
Lots to ponder there! Thanks for your thoughts.
Yes, prior to the last tweaks, it was only on the OD that I was really concerned about.
Just to clarify, I am not perceiving any loss of tone or frequencies or sustain , etc...... with these caps. In fact, even the higher frequencies seem to still be there but simply withOUT the hash. It just makes a richer and more musical tone. I don't hear it muting or lessening any tone that I am wanting to be there.
I have tried lowering some of the gain pots and have actually done so already. The clean volume is now 500k (from 1M). The OD trim is 50k (from 250k). However, when I tried lowering the Mstr Vol, OD level or OD drive ............ it took away from what I was wanting.
Regarding using both plate and plate to cathode caps........... I originally was using larger value caps across plates only, but found if I split those up that I could get by with somewhat lesser values and have a more articulate tone. For example: a .001 across a plate resistor would be swapped out and instead I could use a 390p (plate to cathode) & then maybe a 250p or 390p across that plate resistor and get a clearer tone.
The enhance cap across the LTPI plate resistor has been a HUGE player in smoothing the amp. It also helped allow lower cap values further up in the preamp and OD. I am finding in these higher gain amps (TBM, TOS, SoLow Watt) that the enhance cap is really important to the tone being smooth. Again, I can not hear any loss of high frequencies but simply a smoother high.
Some of the use of the mulitple caps on the OD is partially due to the 5879 tube which is fat but very chimey, IMO. I like smooth more than chime. Just a personal preference. I think without the 5879 that fewer smoothing caps would be needed such as with a 12A_7 tube alone for the OD.
The next thing I am going to try is lowering the 220k into the trim, maybe lowering the 150k into the drive and 150k into the level (all in the OD section). I am thinking that probably only lowering the 220k into the trim will get me what I am wanting which is to increase the blooming effect if possible.
Anyhow, I hope these ramblings and thinking may be useful to others as they tweak and design their own amps?
with respect, Tubenit
-
Observation about the gain stage cathode caps prior to the cathode follower. The cathode caps on that stage seem to really make a BIG difference in finding a sweet tone, IMO. For example, this amp uses a 1.68uf on both the clean and OD cathode cap (gain stage prior to CF).
I find 1uf too thin. I find 2.2uf to have too much grind and not enough sweetness. I tried a 2uf also, but it lost some sweetness compared to the 1.68uf for some reason?
In other words, this seems to be a very sensitive area for component values. Very small changes make some significant differences in tone, IMO.
With respect, Tubenit
I think it's the corner frequency interacting with the resonance of the speaker (~80-120Hz)... What speaker(s) are you using? Does anyone else have some good hypothesis why such small change in the bypass cap could have such dramatic effect? Does this happen with the other 'OD amps as well?
Jaz
-
Same dynamic whether using a Cannabis Rex or Red, White & Blues 12" speaker. No differences with speaker combination.
With the OD engaged, I am now getting the sweetest most musical tone that I've gotten from any amp design I've tried. I do get some of the blooming still with guitar vol on "8" and the amp clean channel vol on "6.5".
However, it is still not blooming as much as the TOS or TOS 2CF. Gonna work on the resistor value going into the trim OD pot and will repost what happens.
Neither my playing or amp sounds like Larry Carlton. Having said that, the amp does have a sweet musical tone like I hear from his guitar/amp when he was with FourPlay. It's a clearer/cleaner OD tone that is very musical.
With respect, Tubenit
-
Great to hear the feedback T & that you seem close. For some these steps are painstakingly dreadful and frustrating, but for others - esepecially you, this is where all the fun and rewards are derived. Yes? ;)
I like the thinking in splitting the difference btwn the plate load and plate-cathode caps and maintaining the tone. I haven't tried the ltpi smoothing cap and have my Tweed-ish amp that needs it to be tried on. When I go from parallel to cascading V1, it could use more of the smoothness you're describing. I don't play it in that mode as much as I'd like because of this and a tweed amp should have a smoother drive to it anyway. Too bad the tweed chassis is so dang small and cumbersome to do much of these things, but I'll find a way to make room it's not to bad to add a cap or two or three...lol.
BTW, yes some of the pot changes will lower your gain and in places you may not actually want. It's just another way to manipulate gain, response, and bandwidth of a stage.
-
What is the transistor and diode for?
-
Do a search on the Mosfet Cathode follower
with respect Tubenit
-
HOORAY !!!!!!!!!!
Amp OD channel sounds FANTASTIC !!!!! Still got the clean harmonically rich OD tones AND now have more of the "blooming effect" and vowel tone. I can even get the blooming tone without the mid switch on & with the clean volume only on "5".
Incredibly sweet musical tones from this. I still need to try it with the digital delay (because that will show up any "hash" in the higher frequencies).
Having said that (short of the delay test), this appears to be a HUGE success for me getting a tone on both the clean and OD that I loved. Typically, I favor one more than the other ........ but both of these are really a sweet musical tone.
I tried about 6 different more tweaks and undid all of them but two (which are indicated in red). Changing the resistor going into the OD drive from 100k lowering it to 47k adds some great ZZ Topish grind complete with that sqwack (sp?) tone that they get. However, it loses a dab of sweetness so I left it at 100k.
The amp now has the "wow" factor that I've been tweaking to try to get. I'll post the revised layout later today or tomorrow. I'll also post some sound clips demo-ing the tone hopefully in the next wk or two.
I'd still give the nod to the original TOS for blues. BUT this is a sweeter more musical tone and is far more versatile in tones that you can dial it.
I am using a 12AY7 in V1 for the clean. And a 5751 in the V2 position.
with respect, Tubenit
EDIT: schematic and layout reposted on the 3rd page
-
Sweet! Actually, the changes you've made aren't all that much from the original design build in your first post to the last one. Three preamp tubes, a mosfet, and three power section tubes (w/out the send/return). Are you using anything special for the iron? I may already have everything I need to get going on this one, it's just a matter of time & when now.
-
Excellent news! Updated schematic saved.
I have a nice, large blank chassis here, so I think I'll just start from fresh with a new build rather than re-work the old amp. But that will have to wait for the Fall (too much grass to mow & other work to do right now).
Thanks for all your work on this T!
G
-
OK, I posted the layout with the schematic. IF there is a discrepency ............ go with the schematic which is correct.
A couple of thoughts ............................
1) I think someone could use a 100k trim pot instead of the 50k pot with 59k resistor going into it?
2) I think a really cool mod to go from a sweet musical harmonic tone to a Billy G crunch, grind and squawk tone would be to have a
paralleled 100k resistor on a spdt switch to switch from 100k to 50k resistance into the OD drive pot
OR
3) Maybe use a 100k pot hooked up as a variable resistor to drive pot. That way you could dial in between harmonics and
grind/crunch/squawk. This would be sort of like the original TOS "fat" switch that is a tone shaper.
I am looking forward to hearing someone's review of this amp. I am very stoked about the tone I am getting!
I should have mentioned that I have a 100uf/100v cathode cap hooked up to a spdt on the 5881's cathodes. I can alternate between 20uf which has a softer more compressed vowel tone to a tighter bass tone with this switch. It's on the back panel of the amp.
With respect, Tubenit
Schematic and layout on the 3rd page
-
IF I were building this from scratch again ...........................
I'd be tempted to add a dumblish-ator on board and use the recovery pot on the front panel as a Master Volume. The Send and Return pots would be on the back panel.
I keep staring at my chassis and how it's laid out trying to figure out if I can squeeze this in somehow?? Unfortunately, I'd have to probably build an entire new board.
With respect, Tubenit
EDIT: Geezer, here is the idea (SCH) that I pm'd you about regarding a D'Mars preamp & OD with FX on board. You could use 16mm Alpha mini-pots for the FX controls .......OR mount the send and return on the back panel and use the Recovery on the front panel as a Master Volume.
-
I was wondering if you might try one more thing??? I've always preferred using the 470r / 10k pi value set-up when driving 6L6s/5881s for a better driving signal to the power tubes. Or have you tried these before and settled with the values of what you're using now?
-
Which power supply node feeds the 5879?
-
Which power supply node feeds the 5879?
Sorry about that. Got left off the schematic but is on the layout. Node D
I was wondering if you might try one more thing??? I've always preferred using the 470r / 10k pi value set-up when driving 6L6s/5881s for a better driving signal to the power tubes. Or have you tried these before and settled with the values of what you're using now?
Haven't tried it. Just adopted the Dumblish values & the amp sounds really good to me with that.
with respect, Tubenit
-
Tried the amp with the digital delay and an hr plus playing til my fingers (not just finger tips) hurt! :icon_biggrin:
This amp (IMO), has an amazingly beautiful musical tone that is so clear and articulate. I am VERY VERY pleased with how this turned out. I am kinda afraid/hesitant to try anything else in the way of a tweak. I don't know what else I could possibly do to get a better tone other then to actually learn how to play my guitar.
The clean is truly clean and rich sounding. Very resonant tone. The cleanish "OD tone" is very harmonically rich and musical. I get some slight blooming even on the cleanish OD now. It just has a very nice clear tone & you could switch from lead to rhythm and still hear every note about as well as if you were actually on the clean channel.
When I switch the midswitch on .............. the notes will blossom reasonably well and sort of open up when you sustain them.
The amp plays note very clearly even when playing faster riffs. I especially like this feature even though I am not much of a fast player like Geezer would be.
The amp is the most sensitive to changing the tone from when you pick lightly or really dig in. Lots of tone available from the playing style & the amp lets it come thru. (In contrast, I've played some amps that however you played the amp sounded pretty much the same).
To give you more of an idea on the blooming and harmonics ............ these are the settings I've been playing on this afternoon & please note that nothing is "cranked" and I am still getting the sustain and sweetness.
Volume 5.5
Treble 4.5
Bass 7 (bass tone is very clear and not muddy or gritty at all)
Mid 4
Clean Master volume 9.5 ( I don't think the amp really needs a master volume on the clean unless one is really wanting to play quietly)
Trim 6.5
OD drive 4
OD level 3.5
PPIMV 6.5
With those settings, all I am doing is changing the guitar volume, guitar pickup or flipping the mid switch. That's it!!!
:thumbsup: :thumbsup: :thumbsup:
Again, sweetest most musical amp tone I've gotten out of any amp.
I am happy happy happy! With respect, Tubenit
-
I wish it was a lower wattage amp. :cry:
-
I wish it was a lower wattage amp
I can't tell if you're kidding or not? :dontknow:
It's cathode biased with 5881's and it's only 23 watts.
At home, I play it at a volume not much different than the Princeton Reverb I had. I can get it close to Deluxe Reverb volume.
With respect, Tubenit
-
T - I'm assuming you're doing all the tweaking w/out the effects loop engaged? How much does the send/return circuit affect things when in use? What I mean is that if it's engaged, you can get extra gain going on there too affecting either channel right?
-
I'm assuming you're doing all the tweaking w/out the effects loop engaged?
It currently just has a passive effects loop. I tweak it without anything in the loop, .......... then try it with digital delay & tweak again if needed. The only thing I typically use in the passive loop is usually a MXR analog delay. I use the Boss digital delay to listen for high end hash.
I am thinking about if I can install an active effects loop mostly to use the recovery pot as a master volume. Not sure I have the room?
with respect, Tubenit
-
I think that I asked you this, about one of your previous builds (TOS, I think). But, are you using the MOSFET just for the economics of not having to add another tube? Or, lack of real estate to add the extra tube? I'm mostly curious as to the sound comparison, MOSFET vs. tube.
Either way, great build. You are very articulate with your descriptions of how each change makes a difference in sounds. Real pleasure to read about your build(s).
Jack
-
I wish it was a lower wattage amp
I can't tell if you're kidding or not? :dontknow:
It's cathode biased with 5881's and it's only 23 watts.
At home, I play it at a volume not much different than the Princeton Reverb I had. I can get it close to Deluxe Reverb volume.
With respect, Tubenit
I guess I didn't look at the schematic long enough. I missed the cathode bias. Might be a good build for me then.
-
...are you using the MOSFET just for the economics of not having to add another tube? Or, lack of real estate to add the extra tube? I'm mostly curious as to the sound comparison, MOSFET vs. tube.
I'm sure tubenit can answer this more completely than I can, as it is his build, but Keen has a great article (http://www.geofex.com/Article_Folders/mosfet_folly/mosfetfolly.htm) in which he describes some positions where MOSFETs might be preferable. In the cathode follower section, he says, "the MOSFET will still be linear when the preceeding plate has bottomed out; a typical 12AX7 triode section just can't "saturate" in normal operation to much less than 50V. When the driver tube is saturated, the MOSFET follower is still happily linear." If linear is what you want in that position, a MOSFET is a great way to get it.
-
I'm sure tubenit can answer this more completely than I can, as it is his build, but Keen has a great article (http://www.geofex.com/Article_Folders/mosfet_folly/mosfetfolly.htm) in which he describes some positions where MOSFETs might be preferable. In the cathode follower section, he says, "the MOSFET will still be linear when the preceeding plate has bottomed out; a typical 12AX7 triode section just can't "saturate" in normal operation to much less than 50V. When the driver tube is saturated, the MOSFET follower is still happily linear." If linear is what you want in that position, a MOSFET is a great way to get it.
Thanks for the link! Got it bookmarked.
Jack
-
It would probably help if I knew what a cathode follower was. Gots to gets me one of dose books....
-
It would probably help if I knew what a cathode follower was. Gots to gets me one of dose books....
Google is your friend.
But basically, a cathode follower is a tube circuit that has it's signal input on the grid and it's signal output is taken from the cathode. The voltage gain is always less than 1 ( typically .8 to .9), but it is capable of driving a relatively low impedance heavy load (as compared to a plate driven load) such as as TMB tonestack or a 100 foot 75Ωz video cable. The output signal is always in phase with the input signal, IE, no phase inversion. It's a mostly uninteresting circuit that can add some very interesting tones to a guitar amp.
-
It would probably help if I knew what a cathode follower was. Gots to gets me one of dose books....
Here's more info, when I posed a question last year about it:
http://www.el34world.com/Forum/index.php?topic=12213.0 (http://www.el34world.com/Forum/index.php?topic=12213.0)
Jack
-
Hi Tubenit,
I updated my 40 watt TOS 2 CF with TAD 6L6WGC to this D'Mars Overdrive Special, WOW!!! The clean channel is so beautiful sounding, I liked the TOS 2 CF clean channel, this amp has even better sounding clear, clean channel. I made one change to the tone stack, I took the jumper off between the bass and mid pots and grounded the bass pot. This gave me a better range on the bass control.
This amp sound really good with single coil or humbucker guitars on the clean channel!! The humbucker guitars have a much more overdriven sound on the overdrive channel than the single coil guitars do. Theo I really like the single coil overdrive sound better IMO.
"(1)I think someone could use a 100k trim pot instead of the 50k pot with 59k resistor going into it?"
I put the smaller resistor before the 50K trim pot, on the overdrive channel and played the amp that way for a day or so. This change softened the overdrive sound, compared to the TOS 2 CF, IMO. I than took out the resistor and 50K pot and installed just a 100KL pot. This change gave me a wider range of the input going into the overdrive channel than before. With this control alone, you can have soft to heavy overdrive.
"(2) I think a really cool mod to go from a sweet musical harmonic tone to a Billy G crunch, grind and squawk tone would be to have a paralleled 100k resistor on a spdt switch to switch from 100k to 50k resistance into the OD drive pot."
I took the 100K resistor, between the first overdrive tube and the OD drive pot and put it on a switch. I tried several resistors parallel on the switch, a 33K and a 50K with the 100K. I ended up with the 100K on one leg of the switch and nothing on the other leg. This is like a boost in overdrive going from 100K to no 100K resistor. They're was not as much of a boost, in the overdrive with the 33K or the 50K resistors. I am pretty happy with the overdrive sound at this stage.
I tried one more change just to see what it would do. I changed the 250k pot to a 100KL on the OD drive control, this gave me less range in that control, but the overdrive sound is now fuller sounding IMO.
I noticed one thing the OD drive control can only go to about 6 before I get a squealing sound, it also did this with the 250K pot. This could be the 5879 tube, is bad or just the way the design works, I don't know.
This amps overdrive can now go from soft to pretty heavy overdrive, with lots of any amount of overdrive in between. This overdrive is more natural sounding than the TOS 2CF IMO.
Thanks Tubenit for all your hard work and tweaks that you have done, to make this a fantastic sounding amp!!!!!!
William_G
-
Any chance you can post a schematic of the changes??? Maybe use one of the editable SCH ones I posted and change it to what you're doing.
I am VERY interested in visually seeing the changes.
The clean channel is so beautiful sounding, I liked the TOS 2 CF clean channel, this amp has even better sounding clean and clear channel.
THANKS of course for sharing the results! I am glad you like the cleaner clean channel. I think it really does sound musically sweeter.
With respect, Tubenit
-
Any chance you can post a schematic of the changes??? Maybe use one of the editable SCH ones I posted and change it to what you're doing.
I am VERY interested in visually seeing the changes.
Yes, please show a drawing of the mods you made. I'm in the process of drawing up my version & would be interested in what you've done.
Thanks to both of you.......
G
-
Any chance you can post a schematic of the changes??? Maybe use one of the editable SCH ones I posted and change it to what you're doing.
I am VERY interested in visually seeing the changes.
Yes, please show a drawing of the mods you made. I'm in the process of drawing up my version & would be interested in what you've done.
Thanks to both of you.......
G
Geezer and Tubenit, Here is a gif of the changes I made to the D'Mars amp. The master Volume was put in before any of the new changes. I built the TOS with VVR the first build than updated to LaMar and than to the Master Volume. I prefer the MV over the other two.
William_G
-
I think the 100k trim pot is a good idea. I would've paralleled a 100k resistor or 68k resistor with the 100k to the drive pot. OR you could switch in series two 56k resistors. The tone stack change might be a good one to do?
Not sure about the change in the Mstr Vol after both the clean and OD, but I think the D'Lite 22 used something similar to that?
THANK you for the information and schematic! I sure appreciate your sharing. I will probably change my trim to a 100k.
With respect, Tubenit
-
Would be really interested in seeing gut shot pics if you are so inclined!
-
I started work on my version of the DuMars today. It's going to be the preamp (only) built into a Valve Jr headcab & chassis.
I always start with the faceplate, so I can use it as a drill guide & be sure everything I want is going fit into the available space.
Here's a pic of the completed faceplate.
(http://img.photobucket.com/albums/v325/jallenshaw/DuMars%20OverDrive%20II/FPDfrontDuMarsIIfinalfaceplatewithdrillguide.jpg)
The pots will have to be 16mm and the knobs will be 1/2" in order to fit everything into the VJr chassis.
I will be using a 3-button footswitch (w/LED's) to control Clean/OD1, OD2, MidBoost
OD1 & 2 are just parallel controls/presets for the OverDrive, switched by relays.
There will also be a "Clean Level" control (a Master Volume that is directly BEFORE the OD relay, and is bypassed when OD is selected....only active when the Clean channel is active)
Everything else will be EXACTLY as Tubenit has in his amp. (including any mods that may arise as I slowly progress thru my build)
G
-
. add an active FX loop (which also works as another OD boost at some level)
Where did the name come from?
Will your FX loop work with a 12AT7? Will it drop right in to an AB763?
-
OD1 & 2 are just parallel controls/presets for the OverDrive, switched by relays.
I think that is a GREAT idea! Especially, since the OD has both such a sweet clean OD and the vowel/blooming tone also. I think you will like that feature ALOT.
Where did the name come from?
D'Mars OD Special (Dumblish OD Special & Marshallish topologies)
Will your FX loop work with a 12AT7? Will it drop right in to an AB763?
It's not my FX loop design, it is used often with Dumble clones. I don't see why it won't work with a 12AT7? I've used a 12AY7, 12AV7 & 12AU7 with it .......... trying various gain levels.
Drop right in???? Not exactly sure what you mean by that? Will it work with a AB763? I think so & don't see why not? Will it be an easy add on? Well, the AB763 is a complicated build already.
With respect, Tubenit
-
Here is the schematic for my version (preamp only)....I still have to work up the layout.
Check me for any errors
The OD pot values are different (doubled) because of the parallel controls.
Also, I will have to diddle with the B+ string to get the voltages needed, but I'll deal with that "live"/after construction.
G
-
Here is the schematic for my version (preamp only)....I still have to work up the layout.
Check me for any errors
The OD pot values are different (doubled) because of the parallel controls.
Also, I will have to diddle with the B+ string to get the voltages needed, but I'll deal with that "live"/after construction.
G
Could you place a DPDT relay before and after (half before and half after) each section so rather than have the drive see both pots it only saw one at a time? WOuld that cause pops? Perhaps the entire OD section could be duplicated (with another tube) and you could just switch between OD sections? Too many parts?
-
Yes, it's done that way to reduce parts count & redundancy.
If you look at the OD Master section, I DID have to use a relay section at the front/entrance, as to be able to have 2x separate tone controls.
G
-
Geezer,
That looks good to me. As an FYI, I am changing my trim pot to 100k. It will have a 22k going into it. Previously there was a 59k into a 50k trim going to 4.7k ground.
With respect, Tubenit
-
Geezer,
As an FYI, I am changing my trim pot to 100k. It will have a 22k going into it. Previously there was a 59k into a 50k trim going to 4.7k ground.
With respect, Tubenit
Let me know how/if you like the 100k after you've installed it.
G
-
OK, it's done and I've had a chance to play it. No oscillation issues at all with the increase. It still has the sweet musical tone & it did allow some more blooming and sustain to take place. Don't know if the 22k was necessary, but I like it so it's going to stay in.
Not necessary, but definitely a useful mod, IMO. What made me consider this is that when I measured the ("favorite") 50k pot settings, I realized I was towards the ceiling so I thought the 100k might allow even more blooming if wanted.
IF you had dual pots for the trim switching, you could do a 50k and a 100k. Just a thought.
With respect, Tubenit
-
IF you had dual pots for the trim switching, you could do a 50k and a 100k. Just a thought.
A good thought! That's the type of thing I hope to do with the "blue" OD (OD1) and the "red" OD channel (Hotter OD2)
Thx, G
-
If you want OD2 to always be hotter, could you put a resistor under the Gain and Drive pots? IOW between the pots and ground. Reverse for OD1 - put a resistor "above" Gain 1 and Drive 1 pots. Depending on resistor values, there would still be overlap in possible levels but you would have different ranges for the two "channels".
Just a late thought,
Chip
-
Hey Chip, Thanks for the idea.....not late at all, as this project will take me weeks to get parts together & work on as I have time.
I will try these ideas on the fly after I have the amp up & running, as needed.
Thx again, G
-
I always love when you guys get together and talk about a build the exchange of idea's is very good. There are always differant angles thrown in that I would never have thought of .
Its such a good learning environment.
Thanks guys Bill :nice1: :happy1: :happy1: :wav:
-
Geezer I really like your dual volume and tone control for the OD channel you can get that 3 channel feel clean, crunch and lead out of it.
Tubnit I have always liked how you have changed tubes throughout this type of amp to get differant gain levels.
I now have a serious stash of tubes to get the perfect combination for each amp, it really does make a big differance.
Bill
-
This sound clip was done rather quickly (about an hr with setting up, recording and mixing it) & the playing is not that great and I was not familiar with the backing track?
This is the new D'Mars OD special amp. I started off on just clean withOUT the mid boost on. Then switched to the OD with midboost switch on. The ONLY thing I did different was flip the DPDT from clean to OD. Nothing else on the guitar or amp was change at all.
http://www.soundclick.com/player/single_player.cfm?songid=11824794&q=hi&newref=1 (http://www.soundclick.com/player/single_player.cfm?songid=11824794&q=hi&newref=1)
For illustration purposes, ......... if 0 is clean and "10" is the OD fully cranked ................ the OD here is around 7. I purposely somewhat cranked the OD to illustrate the range of contrast that the amp can have.
There is a sweet spot that sounds alot like the "clean" channel except with more harmonics, sustain and blooming to it where the notes sort of open up. On that same scale the OD sweet spot would be maybe "3.5 to 4". So this OD tone is cranked beyond that and not as "sweet".
On this clip, the trim is around 7, the drive is around 5 and the level is slightly less than 3. The OD sweet spot is more with the trim around 3-4, the drive around 4 and the level around 7. The PPIMV was around 5.5 (for recording) and I prefer it at "7" or more for the best tone. The tone seems to open up more with the PPIMV dialed 7 or higher.
Hopefully, this will show some of the diversity of the amp. No pedals were used. I added some EQ, very slight compression and some delay in the mix.
With respect, Tubenit
-
I liked it Tubnit it had a real nice clean with a good OD when you kicked it in .
Bill
-
Here's the "Final" schematic & layout I'll be working with.
Will be ordering parts this week & hopefully starting in earnest this weekend or next week.
G
-
Looks excellent! No layout attached.
I think with your relay switching and dual pot controls, that this will be an amazing amp with just about every tonal sound that I would ever want. Very very cool.
Great idea with dual pot controls! I am confidant that will be a winner!
On the clean channel volume after V1a, I think any cap from 300p - 500p will work according to your taste. I was tempted to use a 390p which I also thought sounded very good.
With respect, Tubenit
-
Another possible option, if your B+ voltage to the preamp is high and needs to be dropped anyway: voltage regulator. This will drop the voltage & in the process squish AC wiggle in the B+ supply to the preamp. Might be useful for less noise when the hi gain circuit is switched in.
-
Looks excellent! No layout attached.
The editable layout is on "sheet two" of the schematic attachment
G
-
http://www.soundclick.com/player/single_player.cfm?songid=11824794&q=hi&newref=1 (http://www.soundclick.com/player/single_player.cfm?songid=11824794&q=hi&newref=1)
Sounds really good. A little panning in there toward the end. Be cool to hear some chords/ rhythm playing.
-
On the irf 820 your using for the cathode follower. what type of 12 volt zener are you using 1 watt a certain type I still have problems figuring out zeners .
Thanks Bill
-
what type of 12 volt zener are you using 1 watt a certain type I still have problems figuring out zeners .
I honestly don't remember? I think that might have been addressed in the original TOS2CF thread, but I am not sure?
With respect, Tubenit
-
Any 12v Zener (0.5w or larger) is all that's needed.....it only comes into play as protection for the mosfet if something goes haywire. You could probably use any voltage from 10v to 15v & get the same protection(?)
http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/1N4742A/?qs=sGAEpiMZZMstCHp3EWKGl8HsDsCfnj2su%2f%2fN%2fRFKLus%3d (http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/1N4742A/?qs=sGAEpiMZZMstCHp3EWKGl8HsDsCfnj2su%2f%2fN%2fRFKLus%3d)
Rat Shack might even have something you could use (if you're not already placing a Mouser or Newark order)
G
-
I had a mouser order I needed to place any way.
Thanks Bill
-
Guys,
Any interest in me drawing up a Hoffman style layout board for this D'Mars Overdrive Special ??? I spoke to Doug about it and my impression is that he is open to stocking the boards IF there is a reasonable amount of interest.
Please give me some feedback on this idea. If there are even a few interested, I would be happy to draw up the layout.
With respect, Tubenit
-
At some point I'd certainly want to build it. Right now we are getting ready to remodel the kitchen, which will keep me busy for the next year I'm sure. Plus, my skills are not quite up to all those switches and relays just yet :icon_biggrin: But I'm sure if I'm interested there would be lots of others wanting to give it a try as well.
Just a side note to other "sort of" newbies like myself, I've learned that it is far better to start with simple and work your way up to bells and whistles. At least for myself - I'm pretty sure other guys have picked up the finer points much easier and faster than I have.
-
You guys continue to amaze me with your fantastic sounding designs! I love the clean sounds and overdrive and the way in which you demstrate the touch sensitivity Jeff - VERY tasty.
I've got a heap of 6AU6 pentodes, do you think that would work as a sub for the pentode you guys used? I didn't have much luck with those (5879 if memory serves me). Every one of them went microphonic on me.
Thanks - Craig
-
I've got a heap of 6AU6 pentodes, do you think that would work as a sub for the pentode you guys used
The 5879 sounds better to me , ............. having said that yes the 6AU6 would work fine, I think? When I had a dual 5879 & 6AU6 V1 combination (on a previous amp similar to the HoSo56), I compared each by removing the other. They were not all that far apart in my opinon. I think one of Geezer's HoSo56's may have that combination? Also what worked was the 5654 but read the specs because the maximum voltage is more limited. It was a good sounding tube to me.
I would not hestitate building it with the 6AU6 if you prefer that.
With respect, Tubenit
-
Would this work with ust regular 12AX7s? Would you just need more tube sections?
-
I like the sound of a 6ak5 and wonder if it would be less prone to microphonics and take more abuse in general than any of the "regular" pentodes since it's a high altitude/ high g-force/ high vibration resistant aviation tube??? I have only used it in smaller powered chassis-only amps.
-
I like the sound of a 6ak5 and wonder if it would be less prone to microphonics and take more abuse in general than any of the "regular" pentodes since it's a high altitude/ high g-force/ high vibration resistant aviation tube??? I have only used it in smaller powered chassis-only amps.
6AK5 is same as 5654 (which is the military version). I use them (5654) as V1 in some of my amps....fantastic tube & NEVER had one go microphonic.
G
-
:laugh: oops, I shoud've remembered that but it's been a year since I last looked at one of the data sheets I have. I even bought some of the 5654s too.
-
Can someone please look over this Hoffman style layout board to see if it matches the schematic correctly. I think it does, but I want to make sure before Doug makes some boards.
Once you've reviewed it, just post it's OK or whatever correction may be needed. THANKS!
With respect, Tubenit
-
In just a quick initial look: why a dedicated terminal strip just for the protection diode on the mosfet when it could be easily soldered directly? On the other hand, if you do install the terminal strip and have an open lug then you may as well use is it, such as for the 33k grid resistor soldered closely to the input's tube socket and helping with the connections for the shielding wiring also.
just my layout $.02 worth. Thanks for taking the time to put it together like that for everyone.
-
In just a quick initial look: why a dedicated terminal strip just for the protection diode on the mosfet when it could be easily soldered directly? On the other hand, if you do install the terminal strip and have an open lug then you may as well use is it, such as for the 33k grid resistor soldered closely to the input's tube socket and helping with the connections for the shielding wiring also.
just my layout $.02 worth. Thanks for taking the time to put it together like that for everyone.
I have a question on this in general, not regarding this amp in particular. Is there a benefit to mounting the 1Meg and 33K right at the tube, and using shielded cable from the jack to that point? If yes, would you also want the input jack to be ground isolated from the chassis? This would essentially be like extending the guitar cable all the way to the tube, right? Is there something gained by doing that as opposed to the way Fender did it back in the 60s?
-
If the run is very short then not much if anything is gained by shielding but the longer the run, then yes shielding is always best for low level high impedance signals. This is the most sensitive area that gets amplified the most and anything on the signal here gets amplified on down the chain. The 1M's placement is not important nor which end you ground on one of the side's of the shield's connection.
-
Can someone please look over this Hoffman style layout board to see if it matches the schematic correctly. I think it does, but I want to make sure before Doug makes some boards.
If I get time today, I will try and match up the layout to the schematic
-
If I get time today, I will try and match up the layout to the schematic
If that works out with your schedule, that'd be great! Thanks for offering.
With respect, Tubenit
-
OK, I had a brief break in my schedule and compared the schematic to the layout again (using a highlighter this time).
I am not finding any errors in the layout design meaning that the drilled turret board should match the schematic just fine.
I did find a few small errors in mismatched component values which I corrected. The slope resistor on the layout says 33k and the schematic says 34k (paralleled 68k's). Just use a 33k there.
Once Doug or someone else gives this a final review, I'll give Doug a thumbs up to make layout boards for anyone that wants one.
I think the plates & coupling caps of the LTPI could be drawn differently and perhaps save space ...........BUT I thought someone might not want to use the PPIMV master volume? So this way, the layout board will work well for either.
I think I am getting the best amp tone of any amp I've built from this one. Very fun amp to play.
With respect, Tubenit
-
I was working on it at the same time as you
I did not see your diagrams above so maybe some of the items I have noted have been fixed
All my notes are in red on the two diagrams in my post
print both diagrams out and lay them side by side to match up red areas
Some values I changed because they are more common or may be typos?
Example: people ask me if I stock a .02 cause they don't think a .022 is the same
5uf to 4.7uf - v1a
.02 to .022
.002 to .0022
34k to 33k - by mosfet
.0042 to .0047 - v2b
251p to 250p - v4
4.4uf to 4.7uf - v2a
.00125 to .001 - v2
notes on power supply caps - other values that can be used
20/450v caps - 22/500v or 20/500v
40/450v cap - 1 x 40/500v or 2 x 22/500v or 2 x 20/500v in parallel
16/450v cap - 16/475
10/450v cap - 10/500v
explaination on some of the red areas below:
several pots need to be labeled linear or audio - see red areas
some values on schematic don't match layout like volume pot - 500ka pot or 1ma?
120p cap missing on master vol on layout
I added labels - X and B and tube labels V1, V2, etc on layout
phase inverter layout showing 100k - schematic shows 82k
layout showing 220k resistors at lug columns 29 and 30 - not on schematic
columns 29 and 31 on layout show going to input grids on power tubes - schematic shows they should come from pot wipers on mv dual PPIMV pot?
master vol mising 120p on layout
trim pot is showing 4.7k to ground on layout but missing from schematic
330k resistor on column 30 on layout goes to power supply rail on schematic - goes to column 20 v2b pin on layout
power supply 250 ohm should probably be a 10 watt
power tube cathode cap - 22uf 50v is more common than 20uf/100v?
150k on v2b shows pin 2 on layout but pin 1 on schematic
390p missing between pin 3 and 8 on tube socket of V2 - 5879
let me know if I have all that correct or I am looking at it wrong
I can spruce up the lug layout once everything is corrected
I would add a couple lugs and get rid of the terminal strip near the mosfet
Schematic and layout reposted on 3rd page.
-
THANKS !!!!!!!
Some corrections that you've noted were done in the repost. BUT I will look over your comments and make additional ones that are still needed.
Some values I changed because they are more common or may be typos?
Example: people ask me if I stock a .02 cause they don't think a .022 is the same
5uf to 4.7uf - v1a
.02 to .022
.002 to .0022
34k to 33k - by mosfet
.0042 to .0047 - v2b
251p to 250p - v4
4.4uf to 4.7uf - v2a
Yeah, I agree with changing those. Some of the odd values like the .00125 were the results of experiments and paralleling caps. In this case it was a .001 & a 250p. Same thing with the 4.4uf. I paralleled two 2.2ufs where a 4.7uf would be just fine there. The 34k slope resistor was another experiment of paralleling two 68k's where a 33k would work perfectly.
I like the idea of adding two turrets for the zener/mosfet stuff. That's a better idea.
I'll have to go over the rest of the comments after work today.
I appreciate your help! Overall, it's looking like the actual board is laid out OK with the additions of the zener/mosfet turrets.
With respect, Tubenit
-
actually, maybe don't need two more lugs, depends on how the mosfet is mounted
probably can just jumper the diode across the two mosfet lugs?
a few lugs may be changed like the 220k and 330k resistors noted on the layout
I'll wait for you to go over it all and then I can have a look at the turret layout
-
I took your .sch layout from reply #89 and reworked a few things
I attached the .sch and .gif files
The image file has these areas in red
I didn't try and make the .sch layout real pretty, just moved things around quickly
whole mosfet area was redone.
Hard to tell what rows all those parts go on without doing a paper template layout with the real parts to see if they fit
The 220 ohm and 33k resistors can just jumper in the air to the lugs
330k was moved
added 120p and 390p caps
a few values changed like .02 to .022, 251p to 250p, etc
eliminated columns 4, 29 and 30
dual gang pot goes to input grids on power tubes. I may have G1 and G2 reversed
-
actually, maybe don't need two more lugs, depends on how the mosfet is mounted
probably can just jumper the diode across the two mosfet lugs?
The closer the diode is to the mosfet the better for it's stability, it can make a difference, as per KOC.
Brad :icon_biggrin:
-
OK, I made some more changes from Doug's. I added the values for the pots except the dual gang because I don't rememeber what that is?
I changed some cap values to the ones Doug carries where it would not make any significant difference, IMO.
Some of the paralleled ones like 1.68uf (1uf & .68uf) can be changed to 2.2uf.
The .00125 is one that I would keep. Parallel a .001 with a 250p. I think you could substitute anything between 250p - 500p on the volume pot.
The 330k resistor hook up on Doug's needed to be changed back to be correct with the 5879 tube. Doug's wiring wouldn't have worked (I don't think?)
I still lean towards punching holes for the rows 29 & 30 so people can eliminate the PPIMV IF they want to. Whoever buys the board could decide whether to install turrets in those holes or not?
I will take one more look at it later tonight for any further corrections that are needed. AND I will match the schematic now to the layout & repost it.
'
THANKS for your hard work on this Doug! With respect, Tubenit
-
Joe,
I only do it the way I know works and that is how it is done on all my layout diagrams. I don't know anything about how all those other guys do things. Some of them are way too anal for me personally.
The closer the diode is to the mosfet the better for it's stability, it can make a difference, as per KOC
The way I drew it is that the diode is right next to the mosfet. see the image down below
The 330k resistor hook up on Doug's needed to be changed back to be correct with the 5879 tube. Doug's wiring wouldn't have worked (I don't think?)
I still lean towards punching holes for the rows 29 & 30 so people can eliminate the PPIMV IF they want to. Whoever buys the board could decide whether to install turrets in those holes or not?
Yeah, I looked again at the 330K section again and I had it wrong. It needs to go to input grid 7 which is what I missed.
I was not sure what the 220K resistors were for, but that makes sense if you are trying to make it so you can have the PPIMV or not. Better to have some extra lugs than not.
This is how I would do the 330K section instaed of having the 330k jumping lugs at an angle
-
OK, I think we're good at this point!
Doug, thank you for all your help on this! I like how you did that 330k wiring & changed to that. Makes more sense.
I'd use Doug's 022848 OT (35w) or 018343 OT (40w). You can use his Bassman PT 022798 with a 5V4 rectifier for about 420V on the 6L6/5881 plates. (You can then also switch out to a 5Y3GT if you want to use 6V6's.)
I'd simply increase the B+ dropping resistor to maybe 10k - 22k between nodes B & C. You['ll have to experiment. Main thing is to simply match up the preamp, OD and LTPI voltages. (volts posted in this SCH thread: http://www.el34world.com/Forum/index.php?topic=10776.msg134943#msg134943 (http://www.el34world.com/Forum/index.php?topic=10776.msg134943#msg134943))
I honestly don't think having higher volts on the power tubes will change the tone significantly. The tone is far more in the preamp and OD sections on these D-inspired amps, IMO. You can use 250R/10w to 330R/10w on the power tube's cathodes.
Where you see values of .00125 just parallel a .001 & 250p. 1.68uf just use a 1uf & .68uf. You can use a 100p & 120p for 220p or just use a 250p. You get the idea here, hopefully.
I will go in later (today or tomorrow) and "punch out" the layout board with Doug's layout board design program.
I think this amp is worth building. Best most versatile amp tone I've gotten of any of the designs I've tried.
With respect, Tubenit
EDIT: schematic and layout reposted on 3rd page.
-
I listen to alot of Larry Carlton playing with FourPlay where he uses a less overdriven tone that is fairly smooth. I really like his tone that he brings to FourPlay.
So I wanted to demo that this amp has a very CLEAR overdrive tone. And that it has versatile tone.
The clear OD almost sounds like the clean channel but it's warmer, has more sustain and better harmonics. The clean channel is more percussive, IMO.
Clear overdrive tone with light picking 0- 1:17
Clear overdrive with heavier picking 1:18 -----
Clean channel only 1:30-------
Fat OD 2:05 (note some blooming around 2:09)
Fat OD with delay boosted 2:32
return to Clear OD til end 2:54
http://soundclick.com/share.cfm?id=11842172 (http://soundclick.com/share.cfm?id=11842172)
I am really enjoying the tone that I am getting with this amp!
With respect, Tubenit
-
:smiley:
-
You can use 250R/10w to 330R/10w on the power tube's cathodes.
tubenit, I've seen 250r, 330r, 360r all used/shown on various schems & layouts - which exactly are you using w/ the 5881s?
-
tubenit, I've seen 250r, 330r, 360r all used/shown on various schems & layouts - which exactly are you using w/ the 5881s?
Jeff, Got your most recent schematic and layout. I'll go over them.
As Joe pointed out, the schematic shows a 360 ohm and the layout shows a 250 ohm.
Just mentioning it because both should match to avoid confusion.
Going to match up the two right now
I'll be back
-
I am actually using a 360R, but I have used a 250R also and don't hear much of a difference. Since Doug carries a 250R, I'd just go with that. Measure volts and current and make sure there within what you want (which I would anticipate being fine).
The 360R idea was simply a hanging on left over approach from the first build design I attempted and like.
Again, the preamp and OD and LTPI volts are the critical focal points with this type of D-inspired amp, IMO. I have run one preamp/OD into other amp's LTPI and power amps & still gotten "the sound".
With respect, Tubenit
-
Jeff,
I will change your schematic and layout so that they match the 250ohm
I'll post them back here when done.
Don't update your copies, use mine so that we both have the same changes
i'll be back
-
Larry Carlton playing with FourPlay
love that band...
Earl Klugh Swamp Jazz (http://www.youtube.com/watch?v=6Le8VR8MpfU#)
nice clip tubenit. definitely have some carlton influence happening in that clip.
--DL
-
Jeff,
The schematic and the layout that are attached should now match
Use these two to make future changes so we are all on the same page.
A few notes
The 330K section was still not right. I matched what the schematic showed. Double check it, it should be right now.
I changed the 1.2k and 1uf section around (at the tail end of the ground buss)
The 250P across the 82k plate resistor had a resistor body. I changed it to a capacitor body.
The volume pot is now a 500ka pot on the layout
Pots on the layout were updated to audio and linear to match schematic, but you had better double check them to see if they are correct.
.02's are now .022's
.002's are now .0022's
220p's are 250p
I added wires to E1 and E2
power tube cathode is now a 250 ohm 10w
power supply 250 ohm is now 10 watt
let me know if everything is ok
-
The 330K section was still not right. I matched what the schematic showed. Double check it, it should be right now.
It looks right now! (you're right, it previously wasn't drawn correctly)
I changed the 1.2k and 1uf section around (at the tail end of the ground buss)
That looks waaayy better to me. Good job.
If you're good with it, let's call it a wrap.
Thanks!!! With respect, Tubenit
-
Tubenit -
Between the two clips you have done a great job demonstrating the versatility of this amp - WOW :occasion14:. Thanks so much for all you do and share with all of us!! :worthy1: You are a fantastic resource for anyone wanting to build a guitar amp!!!
Is this latest clip with the single 10" ragin cajin speaker? Thanks again!!
-
The 330K section was still not right. I matched what the schematic showed. Double check it, it should be right now.
It looks right now! (you're right, it previously wasn't drawn correctly)
I changed the 1.2k and 1uf section around (at the tail end of the ground buss)
That looks waaayy better to me. Good job.
If you're good with it, let's call it a wrap.
Thanks!!! With respect, Tubenit
I need to print out a paper template to make sure the spacing is right on all the parts.
Then I will know the exact lug hole placement
I'll print out a template and check the lug layout and then get back with you
-
Doug, thanks again for the help! I know you're very busy and I realize you've put quite a bit of time on this.
Is this latest clip with the single 10" ragin cajin speaker? Thanks again!!
Emminence Cannabis Rex on this one. I like the Red, White and Blues also. Having said that, I think there are a number of speakers that would well with this amp, IMO
With respect, Tubenit
-
I just have to wire up the pots and relays, then mine will be up and running. Can't wait to get this thing going.
If my "preamp only" works out, I will probably build a full amp using the Hoffman layout.
Thanks for all the work on this!
G
-
then mine will be up and running. Can't wait to get this thing going.
:happy1: :happy1:
I can't wait either !!
IF at all possible, and you've got time, please post a sound clip when you're done tweaking everything. I'd love to actually have some actually good guitar work showing what this design is able to do. I think this amp is waayy better than my playing can show.
With respect, Tubenit
-
Jeff,
I looked at your 330k section, it's the same thing as what I have, just different.
I have already drawn up the lug layout in my CAD program, but I can change it.
The CAD program then creates the lug drilling file for the CNC machine
Here's an image file of what that board layout looks like
Check it out and see if it looks ok
I moved the 250 ohm 10 watt cathode resistor down to the last set of lugs and skipped one column
The 10 watt needs some breathing room from the cathode cap so the cap does not overheat.
-
Looks excellent! Great job!
I'm supportive of that being the final version. I think the board is laid out well and will be very tweakable if someone is wanting to do that.
I'll write up a Bill of Materials in the next day or so & post it along with the revised schematic and layout in the SCH files and then post on this thread that I have done so.
THANKS! With respect, Tubenit
-
I'll send you a board with lugs so you can build it and see if everything is as it should be.
Let me know if I can go ahead and cut a board
I'll install the lugs
-
Sounds great! If I can get a board from you, I'll get it built!
Thanks, Tubenit
-
I've attached a capacitor "guide" to show what caps that I would use where.
I'd used Orange Drop in the clean channel. Use Mallory 150's everywhere else except the .1 where I'd used Xicon for size convenience.
with respect, Tubenit
-
I updated my CAD drawing for your cap colors
I stock a dual gang 250kl pot. Is that what you are using?
On your BOM, I think the .68 caps are supposed to be 1.68uf
If you want, you can update your layout digram to match my CAd
I moved the 330k and .1 lugs up to the top row
see Pic below
-
I stock a dual gang 250kl pot
The PPIMV would be best being a 250ka.
Regarding the 1.68uf
I know it sounds kinda goofy.......... but I paralleled one of your 1uf with a .68uf. I can imagine that it sounds picky; BUT for some reason, a 1uf sounded too thin and a 2.2uf was a little more "something" than what I wanted and the 1.68uf sounded spot on. Others can either use a 1uf or 2.2uf and try it for themselves.
EDIT: updated schematic and layout to reflect the 250ka PPIMV
With respect, Tubenit
-
I redid the mosfet section because the lug spacing would not have been right for a TO-220 body mosfet
The leg spacing is 5mm to the two outside legs and so I made that the spacing on the turret board lugs
The zener diode sits right next to the mosfet
Here's an update of how my CAD drawing looks and a bit of board with some test holes drilled
-
Wow! That looks fabulous! Very cool.
Thanks! Tubenit
-
Going over the schematic and comparing to the parts list
These items differ from the parts list
1/2 of PPIMV still shows as 250kl on schematic
220r 3 watt shows as 1 watt on schematic and layout
68r should be a 680r
The quantities on the left are what I actually found and are different from the parts list quantites
2 - 1.5K 3 watt
2 - 100 ohm
1 - 820 ohm
1 - 6.8k
1 - 27k
2 - 68k
2 - 82k
3 - 1m
1 - 4.7m
3 - 1uf
-
These items differ from the parts list
1/2 of PPIMV still shows as 250kl on schematic
220r 3 watt shows as 1 watt on schematic and layout
68r should be a 680r
The quantities on the left are what I actually found and are different from the parts list quantites
2 - 1.5K 3 watt
2 - 100 ohm
1 - 820 ohm
1 - 6.8k
1 - 27k
2 - 68k
2 - 82k
3 - 1m
1 - 4.7m
3 - 1uf
Thanks for helping and having a great eye for detail. Should all be corrected. New Bill of Materials attached.
Reference SCH information here :
http://www.el34world.com/Forum/index.php?topic=14302.0 (http://www.el34world.com/Forum/index.php?topic=14302.0)
Tubenit
-
Thanks for helping and having a great eye for detail
That be one of my specialties :icon_biggrin:
I like ironing out details like the mosfet/zener lug section. The parts fit the lugs perfectly
BTW, how hot does the mosfet get?
Does it need to be heatsinked?
-
BTW, how hot does the mosfet get?
Does it need to be heatsinked?
Does not need to be heatsinked from what I understand. I did this on two amps with no issues not being heat sinked.
With respect, Tubenit
-
Got thrown a "curve" today.......hooked up the relays & there wasn't enough current to run the 4x of them (plus the 4x tubes) so I had to install a dedicated 6.3v trannie (which I just happened to have on the shelf!)
Got the relays working, just have a few wires left to solder from the pots to the relays & tubes. Probably have it up & running by Saturday fer shur..... :guitar1
-
Got thrown a "curve" today.......hooked up the relays & there wasn't enough current to run the 4x of them (plus the 4x tubes) so I had to install a dedicated 6.3v trannie (which I just happened to have on the shelf!)
Just curious about the rating on your main trannies heater winding?
Must be pretty low?
-
Valve jr PT that originally ran a single 12ax7 & EL84, now running 4x tubes, one of them a 600 ma recto
-
Ah, ok, that makes sense
-
Ok Jeff,
Your D'Mars board is done and is going out with your parts today
I am still not happy with the 1.2k to 1uf section below the phase inverter lugs
The 1uf body is too large to span the lug gap.
It may be better just to go from the 1.2k right down to the ground buss lugs at an angle.
You can see how that goes when you load the board.
The wire that goes from the drain on the mosfet is under the board, which makes more sense
I am changing that on my CAD drawing to a dotted line and a note that it goes under the board.
I added the two main ground wires
I included 4 screws, nuts and standoffs
Here's a shot of your board and my cad program layout
-
After building the board and lacing up the lugs, I updated my CAD drawing with these two changes
Dotted line for under the board wire that goes from mosfet drain to the power supply rail
1uf body seems to be a better fit by mounting it at an angle from the 1.2k to the ground buss lug shown in my screen shot.
-
EL34,
THANKS! That board looks fantastic! Very cool. :worthy1:
Looking forward to populating the board. I'll definitely do my best work & post some good pictures when done.
Again, I truly appreciate the generousity of your time and effort helping all of us out on the forum. I know you're busy and that you put some significant time in on this.
This is going to make it much easier for others who are interested to do this build. Schematic (editable), layout, parts, Bill of Materials and a Hoffman style board is a good foundation to work from.
I'm looking forward to hearing reviews by others who build this on how they like this amp and what tweaks/mods they might add to theirs.
With respect, Tubenit
-
I added my CAD program layout to the post up above
-
Doug, if you're ready, I'd love to get one of those boards...I need some other parts, so just let me know how I can add it in my shopping cart.
Thanks again for all of your hard work.....you guys have made this idiot proof.
-
I would like to wait and see if it requires any changes
Once Jeff builds it we will know.
You can't really tell if a lug layout is perfect until the board has been poulated
-
Ok, no problem, and no rush....I'm excited to get going, but you guys are saving me about 72 hours of triple checking all of this stuff....It's really the part of the project that makes me craziest and just takes ME way too long...I worked on my last layout for 2 weeks and my wife thought I was nuts....maybe she's right.
Jeff, thanks so much for all of your work and the sound clips that tie it all together....priceless
-
BTW, the boards don't come with the lugs installed and laced together like in the picture shown above.
They will be a drilled board like the ones you see on this page
http://www.hoffmanamps.com/MyStore/catalog/parts12.htm (http://www.hoffmanamps.com/MyStore/catalog/parts12.htm)
You have to install the lugs, lace the lugs and drill the four mounting holes.
-
I knew I should've put that in there...I was gonna say," I am aware that the board will come bare"...but, as usual, you are very clear in your description :thumbsup:
I am assuming that when it's ready for sale, it will appear on the boards page in the store.........in the meantime, I'm gathering some backing tracks in preparation :icon_biggrin:
-
I'll post back when they are added to the catalog pages
-
Just got the mail & the layout board is in it! Yeah!
Guys, I placed the parts order yesterday morning! How is that from prompt service!! Hands down, Doug's got all of them beat.
This board looks fantastic to me. I have somewhat of a busy wkend ahead, but I'll start on it this wkend and do my best work on neatness. Probably will post pics next wkend hopefully of the completed board.
EL34, the lug lacing looks incredible. Remarkably neat and organized job. Very impressive.
THANKS & with respect, Tubenit
-
I am the fastest ship in the shipping business.
Stole that line from UPS, but it is true.
Have fun with your new build
-
He laces boards by day. And steals down from the mountains by cover of night to put little jewels in our mailboxes.
-
No, I lace one board by day and drink beer by night while the slave elves do all the hard work.
"Back to work you lazy little grub eaters"
-
No, I lace one board by day and drink beer by night while the slave elves do all the hard work.
"Back to work you lazy little grub eaters"
:l2:
Watch out that the little buggers don't go on strike for gold and silver instead of grubs, just like Santas little guys did.
Brad :l3:
-
The elves must polish my Gold and Silver stack in the sub terranian vaults
-
The elves must polish my Gold and Silver stack in the sub terranian vaults.
:l3:
-
You know I'm gonna come see you one day. And we'll bash some elves and drink some beers. And hopefully swap some tunes. :wink:
-
Man you guys are mean!
Brad :l2:
-
A big THANKS to EL34 for making this board!!
It is laid out quite well & was very easy to wire up. He got the spacing "spot on" for the components.
Board is 10" x 3 &1/8".
The board in the picture is not quite finished and needs a mosfet, different B+ resistors, .033 post LTPI coupling caps and 220R/1w resistor going into the mosfet. (while I don't have the mosfet installed, EL34 posted a pic in an earlier post showing that the spacing he used works well with the mosfet)
However, it does show how well the components fit. About a 2.5 hr wiring for me. I installed the components into the turrets and then came back and soldered them in short order. I made a component bending jig out of wood to help facilitate ease of bending the components to fit the spacing. Only took about 5 minutes to make the wood jigs.
With this predrilled Hoffman D'Mars layout board, the schematic and layout drawing ......... making this amp should be reasonably easy.
As an FYI, I don't have a drill press, but the boards I've built have been easy to install turrets using his staking instructions
(search "tools" and Hoffman Library of Information http://www.el34world.com/Forum/index.php?topic=9800.0 (http://www.el34world.com/Forum/index.php?topic=9800.0)).
I will repost again after I get the remaining parts and finish the board.
Ordered the board parts Thurs am, got the board and parts Fri, got it populated in a few hrs on Sat ............... how's that :icon_biggrin:
With respect, Tubenit
-
Alrighty......mine is up & running! :guitar1
Worked perfectly from the 1st startup, and sounds fantastic! I haven't even started "tube rolling" yet, just stuck a 12AY7/5751/5879 in there & she took off!
The tone of the clean has a Fender sparkle at lower gain settings, & gets a nice Marshally grunt as you turn up the gain. The MidBoost used with the clean channel gives a convincing pentode-like tone.
The OD is indeed the "clearest" I've gotten yet, and a wide range of tones is available with different control settings.
Build it just as Tubenit says, with all his values & voltages. I had made some changes to the "Red" channel of my OD section (changed some limiting resistor values) but reverted to match the original values, which is what I used on the "Blue" OD channel, which sounds perfect. So both of my OD channels are now "stock" and give any variation of OD tone I want at the click of a foot-switch.
I am attaching an updated schem & layout. Use this as a reference ONLY IF you want to do the multi-channel OD switching like I have done. If that's what you want, then refer to the pots & relay wiring to see how that was done. Use the Hoffman board for the best possible layout & just add the switching mods. Otherwise, adhere strickly to the Hoffman schem & layout that is posted.
I'm off to try some different tube combinations to see if any improvement (to my tastes) can be had.......
G
-
Cool beans
Two builds going on at the same time
Jeff, You add your parts to the board first and then wire up last?
I wire up the board in the chassis and add the parts last.
Just curious if you find it difficult to wrap wires around the lugs with the parts in the way?
-
The tone of the clean has a Fender sparkle at lower gain settings, & gets a nice Marshally grunt as you turn up the gain. The MidBoost used with the clean channel gives a convincing pentode-like tone.
The OD is indeed the "clearest" I've gotten yet, and a wide range of tones is available with different control settings
Hooray !!!!!! :thumbsup: :thumbsup: Man, I am excited that it got that clear OD tone for you! Mega cool!
Jeff, You add your parts to the board first and then wire up last?
I wire up the board in the chassis and add the parts last.
Just curious if you find it difficult to wrap wires around the lugs with the parts in the way?
Doug, you rascal !!!!! :l2: :l2: I started laughing when I read that.
Sometime waayyyy back, I saw a populated layout board that you had done and figured you populated the board first and then wired it into the amp. So, I got the idea from you!
:dontknow: :icon_biggrin:
Anyhow, yeah that works fine and it's not been a problem wrapping wires around the lugs that way. I just use small needle nose pliars. No issue there.
Geezer, I know you're a busy man .............. BUT I'd love to hear soundclips from you when it's convenient for you. It's been a long time since I've had the pleasure of hearing your magnificent playing. No rush, but I hope you'll share something at some point.
With respect, Tubenit
-
Sometime waayyyy back, I saw a populated layout board that you had done and figured you populated the board first
I am not sure where or when that was?
Anywho, just for the record, I always install the board in the amp, do all the wiring and then add the parts last.
Just my method, whatever works for you is good.
-
I am not sure where or when that was?
You have really got me chuckling with this one .............
Always refer to the current Hoffman Library of Information! :l2: :l2:
It's a marvelous source of information. These pics are where I got the idea that you populated the boards first. :grin:
With respect, Tubenit :icon_biggrin: :icon_biggrin:
-
I'll have to try & remember how to do sound clips....it's been a long time! :think1:
I noticed that I had a LOT of gain on tap on the OD controls with the 5751 in V2, so I tried another 12AY7 (same as V1) & it gave me a great tone & alot more "headroom" on the OD controls. So far, I think the AY is gonna stay! So I'm running 12AY7's in both V1 & V2.
The amp sounds especially nice with the Telecaster.....chimey on the cleans & Robben Ford-like tones in MidBoosted OD mode! SWEEET!
With the MidBoost on the footswitch, I have 6x levels of Clean to OverDrive by just stomping on the pedal.
Going back to the shop to play some more!
Thx for the great design!
G
-
These pics are where I got the idea that you populated the boards first
Ah ok,
I can see how that would be misleading.
Those are the Hoffman board kits that I sold maybe 15 years ago and so I took pictures with the parts on them so people could see what they looked like when loaded. They arrived like that to the customer, but that's not how I installed them.
I never installed them with the parts on the board since it was so much easier to install the board without any parts.
But I found out that many people find it hard to do without looking at a part on the board for reference.
Hard to say after all these years if I have any instructions on how I actually installed the boards at my shop
Another plus to installing the board wires first is that you can clean up all the solder flux spots before you add the parts.
This makes the boards look really nice without tons of flux spots.
The flux seems to pop and spray everywhere as it heats up.
Again, this is just something I have in my brain because it's how I used to do it.
Probably the best info are the build pictures on the library page of some of my projects which show step by step how I build things.
Like the Revibe
http://www.el34world.com/projects/images/Img_6805.jpg (http://www.el34world.com/projects/images/Img_6805.jpg)
-
I was thinking this could be a possible easy OD switching idea. I have mentioned that there is this very clear OD tone & by changing the trim and level OD pots that you can dial in a FAT OD tone.
My chassis simply doesn't have room for any more pots. Geezer dual pot controls for the OD is ideal, IMO. However, since that is not currently an option with this chassis, .......... it occured to me that I could the following:
place a resister between the trim pot and ground & then parallel a resistor across the level pot. Let's say that the trim at "3" with level at "6-7" is a great clear OD tone and the fat OD tone involves the trim at "7" and the level at "3-4". NOTE: this means switching from clean OD to FAT OD withOUT boosting the volume. Just a different tone. I can boost the trim from "3" to "7" with a resistor between pot and ground.
And I can reduce the level from "7" to "3.5" by paralleling a resistor across the pot terminals.
This could be done with relay switching. So, the amp could have the following foot switch operated relays:
clean to OD
mid boost
clear OD to FAT OD (keeping those two volumes the same)
Haven't worked out the values yet, but I can experiment and report back. Doing this does NOT change anything on the D'Mars Hoffman board. The board would still work perfectly with this mod.
With respect, Tubenit
-
OK, I had a chance to try playing the amp for over an hr to see IF the idea of a relay switching those resistors will work. And the answer is yes! I marked where the trim and level pots need to be dialed to get the clear OD or FAT OD at the same volume.
I am really loving this amp & feel like this is the best tone that I've gotten. I'll offer these observations of the amp.
I am rarely changing the setting on the clean volume, clean tone controls or clean master volume. Those are pretty much "set and forget" for me.
Clean volume is set at about "6.5" about 95% of time and only occasionally boosted to "7.5" which does allow more blooming. The clean master volume could actually be removed for my purposes, but perhaps playing at quiet bedroom volumes could be useful.
I set the clean tone controls to what I like. Then adjust the OD tone control to how I want the tone on the OD to sound. I set and forget those. Any further tone changes will be the 5-way switch on my guitar or guitar tone control.
I am finding it the easiest to change the volume using the PPIMV or the recovery pot on the active FX (D-lator). or the guitar volume.
IF the FX is hooked up, then I use the FX recovery pot on it 90% of the time to control the volume of the amp & hardly touch the PPIMV. However, the PPIMV is still useful without the FX and to reduce volume to recording levels.
The clear OD does sound comparably clear as the clean channel but with greater sustain. The FAT has a more pushed/overdriven and less clear tone.
Even with the clean volume only on "6.5", I can get almost endless sustain & bloom on any note from 8 ft away from the amp IF my guitar is "9" and the PPIMV is above "8". There is an increase in blooming if the clean volume is up to "7.5", but I don't think it is as musically sweet, IMO. This is with the FX box set at Send/6, Return/6 and Recovery/6 or higher.
The FX box set at Send/5, Return/5 & Recovery/6 is pretty much the same volume as the amp withOUT the FX engaged in the loop.
The midboost on the amp is VERY functional and dramatically changes the tone. AND I like the tone both with the midboost on .......... OR off. The midboost plays a major roled in the blooming feature. Very very little blooming with the midboost off. I can get some blooming with the clean channel and midboost on some notes but apprently not on all of them.
All of this is with the V1 being 12AY7 and the V2 being 5751. Obviously with 12AX7's the gain could be significantly increased but with the loss of musical "sweetness", IMO.
It is possible to match the volume levels between the clean channel, clear OD and FAT OD tones.
More later...................... With respect, Tubenit
-
Is that with the turret board or are you dialing in your first build?
-
Is that with the turret board or are you dialing in your first build?
This is dialing in the first build. However, I would expect similar if not identical results with the turret board.
(It should be noted that this original D'Mars OD Special was built with your turret and your board material.)
With respect, Tubenit
-
OK, here's my final version (schematic attached)
FANTASTIC amp! I only made a few small changes to suit my taste....
Lowered the bright cap on the Clean Gain fron 470p to 270p to better suit my guitars. Ideally, a multi switch would be good for selection of different bright caps for different guitars.
Biggest thing I did was change from a "MidBoost" (.002 cap replacing the picofarad cap in the tonestack, to boost the mids) to a "PAB" (pre-amp boost or "raw" control) accomplished by lifting the mid pot slightly from ground to give a more subtle mid-boost.. This gave me a cleaner/clearer boost (again, to my ears & with my guitars....just a personal preference)
Everything else is exactly as Tubenit had as the "stock" values.
I am going to build the full-on amp this winter, including the tube buffered effects loop, using a nice 80's set of 100w iron I have, running 4x6L6/5881 cathode biased for ~50w
THANKS to Tubenit & Doug for all the work on this......having the pre-laid out & drilled board will be a HUGE help when I do the full amp build!
Geezer
-
Cool, sounds like it's another great design by Jeff
I would like to see a pic of all the realys and how you have them laid out if possible.
-
Cool, sounds like it's another great design by Jeff
I would like to see a pic of all the relays and how you have them laid out if possible.
I cheat.... :icon_biggrin:
I use the Weber 4x relay board....very compact.
(https://taweber.powweb.com/store/chansw-4bd.jpg)
-
Haaa, no I meant as they sit in the amp itself.
I should have more specific.
I always like to see how long the signal wires are and where the relays sit in the actual circuit chain.
-
Geezer -
As I understand it - you built a preamp. Is that right? If so - what power amp setups have you run your preamp with at this point? thx.
-
Tubenit's & Geezer's realizations are always Killer
this has also the contribute of Doug
what can we wish more ?
:bravo1:
K
-
Geezer -
As I understand it - you built a preamp. Is that right? If so - what power amp setups have you run your preamp with at this point? thx.
I'm running it into a 4x 6AQ5 (NOS Tung Sol's) power amp. So basically the same a 4x6V6 cathode biased.
-
Any chance you can post a schematic of the changes??? Maybe use one of the editable SCH ones I posted and change it to what you're doing.
I am VERY interested in visually seeing the changes.
The clean channel is so beautiful sounding, I liked the TOS 2 CF clean channel, this amp has even better sounding clean and clear channel.
THANKS of course for sharing the results! I am glad you like the cleaner clean channel. I think it really does sound musically sweeter.
With respect, Tubenit
First, congrats on yet another great design. I am way behind on my builds - I'm not even done with the original TOS yet, and you guys are already onto TOS CF, D'Mar OS... :worthy1: But I noticed that the designs' topology stayed pretty much the same with some tube rolling and various tonestack, OD gain level tweaks. So my questions are - 1) is the 5789 primarily responsible for setting the tone for OD, 2) does whichever tube in V1 set the tone for the clean and 3) which version is the most suitable for classic rock/blues?
Thanks,
Jaz
-
Q1 yes, the V1 sets the clean tone
Q2 yes, the 5879 is largely responsible for coloring the OD tone
Q3 I think either amp is great for rock or blues. The D'Mars is closer to Eric Johnson clear tones. The TOS is a great blues amp but
can not match the clean tones of the D'Mars. But the TOS maybe has a fatter OD tone.
IF I was trying to play a ZZ Top blues heavily driven blues tone, I'd pick the TOS.
Probably would pick the TOS for Gary Moore tones or Robin Trower tones also.
IF I was trying to imitate Eric Johnson or the clear OD blues tones of Joe Bonamassa, then I'd lean toward the D'Mars. IF I was
wanting the clear OD tone of Larry Carlton playing with FourPlay, then I'd definitely use the D'Mars.
That's probably the best I can describe it, unfortunately. :dontknow:
Hope that helps! With respect, Tubenit
-
It definitely helps, it seems the TOS might be more suitable for me.
Thanks,
Jaz
-
Doug, you asked Geezer about relays placement
I hope you think it will be possible to you to add relays sockets (using your turret style) to the layout of the board as to have the versatile dual control version designed by Geezer
could you do such a thing ? :icon_biggrin:
(http://www.el34world.com/projects/images/DSCN1798B_small.JPG)
I know, this will be a further effort, but I'm sure many people will be glad to you !
K
-
I have not studied the signal chain to see where realys would be located.
Still have not seen Geezer picture of where his are located
-
With my chassis layout, I have the relay board mounted on the chassis top/bottom similar to how I mount the layout boards.
The relays are between the layout board and the front panel & pots. The relay I am using is somewhat off center and to the side somewhat.
I currently only have one relay but I am going to change that to 3 relays for clean/OD, mid boost and clear OD/ FAT OD.
I attached Geezer's layout also, but I am not certain exactly where the physical location of the relay board is? I am guessing it is similar to what I use and between layout board and pots.
Hope that helps. With respect, Tubenit
-
Your relay location makes much more sense than having it on the turret board.
Having relays on the board takes up lots of space and means a longer board.
Then, some people don't want relays and so now what, have two different board designs?
Also, I like the idea of 3 relays in a row instead of how the weber board is laid out.
A layout end to end like this would take up much less space and would be a better fit into most chassis, IMO
-
Q1 yes, the V1 sets the clean tone
Q2 yes, the 5879 is largely responsible for coloring the OD tone
Q3 I think either amp is great for rock or blues. The D'Mars is closer to Eric Johnson clear tones. The TOS is a great blues amp but
can not match the clean tones of the D'Mars. But the TOS maybe has a fatter OD tone.
IF I was trying to play a ZZ Top blues heavily driven blues tone, I'd pick the TOS.
Probably would pick the TOS for Gary Moore tones or Robin Trower tones also.
IF I was trying to imitate Eric Johnson or the clear OD blues tones of Joe Bonamassa, then I'd lean toward the D'Mars. IF I was
wanting the clear OD tone of Larry Carlton playing with FourPlay, then I'd definitely use the D'Mars.
That's probably the best I can describe it, unfortunately. :dontknow:
Hope that helps! With respect, Tubenit
Thank you very much for the description, this is very helpful.
Now I guess I have to build both ...
BTW: how important do you think is the IRF820 for the tone? I am thinking of simply omitting it since I have built a two stage preamp close to a plexi w/o a cathode follower, and that is a fine sounding amp indeed.
Cheers Stephan
-
how important do you think is the IRF820 for the tone?
That is a very good question! I am confidant that the cathode follower then the tone stack is VERY key to the tone.
I am uncertain about the IRF820 mosfet specifically? My guess is that the mosfet may possible create a more high fidelity tone than a CF triode, but I have no way of knowing that? I am thinking the "high fidelity tone" may be useful in simply recreating a previous tone signal without coloring it much? I do like the clean tone on this amp very much.
Hopefully someone who actually knows can comment on this?
With respect, Tubenit
-
Thanks for replay
I was thinking to a board with relays on it a la Larry, I really like his constructions http://www.larryamps.de/ (http://www.larryamps.de/)
(http://www.larry-amplification.de/cms1/sites/default/files/styles/large/public/BP%20Guts%203%20240209.jpg)
instead you were thinking to a separated board with the relays on line .............. a la Larry :icon_biggrin: :icon_biggrin:
(http://www.larry-amplification.de/cms1/sites/default/files/styles/large/public/RockWizard_37.jpg)
Two different solutions, both very elegant :grin:
Can we hope for the layout of a small dedicated (turret or eyelet) add on Relays Board ?
K
-
Yes, that skinny little board in the bottom picture is more what I was thinking of.
-
On the attached schematic, I am thinking that one would need a 4700uf cap for each relay? Is that correct?
And the LED light would not be needed IF the footswitch already had one correct? The LED is simply to show that it's on?
Can someone confirm that those particular relays are relatively quiet with no hum?
With respect, Tubenit
-
The 4700uf/16v cap in my relay diagrams is for the relay power supply.
You can share that power supply with more than one relay
That drawing I posted for two relays and one switch on one of your other post shows how that would work.
-
Can someone confirm that those particular relays are relatively quiet with no hum?
to which relay do you refer ?
I think that shielded relays are more safe than plastic case relays
but in my previous post you can see that a guru like Larry uses both type
so I assume that also relays like those posted by Doug are fine
Omron is a well known brand and many manufacturers use their products
(http://www.el34world.com/Forum/index.php?action=dlattach;topic=14201.0;attach=31735;image)
K
-
On the attached schematic, I am thinking that one would need a 4700uf cap for each relay? Is that correct?
No, that is in the relay power supply filter cap.
You can supply several relays with that power supply, so you just add more relays to the + and - leaving that power supply.
See my attached diagram below from your other post about multiple relays
You build the relay power supply and then supply the relay coils with power from the power supply
Each relay coil has a switch that switches the power to the coil on or one switch can switch on several relay coils.
And this page shows a few different ways to build that relay power supply based on what type of power tranny you have
http://www.el34world.com/projects/relay_switch.htm (http://www.el34world.com/projects/relay_switch.htm)
And the LED light would not be needed IF the footswitch already had one correct? The LED is simply to show that it's on
yes, the led is only there to indicate that the relay has been switched on.
You can delete the led and the 180 ohm resistor if you don't need them
Can someone confirm that those particular relays are relatively quiet with no hum?
Well yes, that's exactly why I stock those relays. They are Omron low signal switching relays
-
On the attached schematic, I am thinking that one would need a 4700uf cap for each relay?
That cap is for filtering out the ripple from the PSU. As long as the PSU can supply the needed voltage and current you can add as many relays as you need.
Brad :icon_biggrin:
-
The signal switching relays I sell only draw 40ma for the coil so there's lots of power in that power supply
-
THANKS for the info and responses regarding the relays! I am going to work on drawing up a relay turret board and will post it sometime in the next few days.
Following Geezer's innovative lead regarding dual OD pots .........................
I have VERY limited chassis space, but I figured if I remove the clean MV (which I seldom use), then put the OD drive on top of the chassis (set up more like a trimmer), & then put 2 Trim pots and 2 OD level pots on the front ............. I can make this work.
This idea will work fine with the Hoffman style board. No issues with that at all.
IF I have time, I'll try to redraw the Hoffman layout to reflect this idea.
With respect, Tubenit
-
Yes, that skinny little board in the bottom picture is more what I was thinking of.
I need a board like this too. I bet a lot of folks do. A long version we can cut the number of relays we need from would be cool.
-
And this page shows a few different ways to build that relay power supply based on what type of power tranny you have
http://www.el34world.com/projects/relay_switch.htm (http://www.el34world.com/projects/relay_switch.htm)
Is it possible to do this with the unused 5V(?) tap on the PT that would have normally been used for a rectifier tube? If you use the 6.3V heater tap does that mess with the heaters? IOW do you have to use a separate transformer (and find a place to put it)?
-
Is it possible to do this with the unused 5V(?) tap on the PT that would have normally been used for a rectifier tube?
Sure, there are type of Omron relays that has 3v - 4.5v - 5v ..... till 48v
see datasheet here
http://docs-europe.electrocomponents.com/webdocs/00b6/0900766b800b6042.pdf (http://docs-europe.electrocomponents.com/webdocs/00b6/0900766b800b6042.pdf)
K
-
Building on Doug's previous work generously posted in the Library of Information, I drew this up.
Can someone PLEASE look over the Relay Layout Board and confirm this is drawn up correctly and is consistent with Hoffman's schematic ?
Once this is confirmed as correct, I'll try to draw up another board with multiple relay switching and a 5pin DIN plug.
With respect, Tubenit
-
I changed some things
You don't need two 4700uf caps
I think I did that on the stout because I was chasing a hum problem and so I made a two stage power supply with a resitor between the two caps
Turned out the relay was too close to the fuse holder on the Stout and it was not the relay power supply
The common on the relay is one connection point and either the normally closed or normally opened is the other
In your drawing 6 and 11 are the normally closed connections
9 and 8 are the normally open connections
-
That circuit will be fine for one relay, but may not work as expected with 2 or more relays.
Consider this...
1. Doug's relay wants 40ma @ 5VDC. (It will work at less voltage and current but may not reliably operate)
2. 6.3VAC and a bridge will produce 8.9VDC unloaded. (Let's call it 9V to make the math easier)
So, we need to drop 4 volts across the resistor. Using a 100Ω resistor will do this nicely and will allow 40ma to flow (I = 4V\100Ω = 40ma). Thats perfect for one relay coil.
Now add a second relay. Each relay wants 40ma for a total of 80ma. This 80ma must flow thru that 100Ω resistor. The resistor will now drop 8 volts (.08ma X 100Ω = 8V) That only leaves 1V for the relays.
Add a third relay and the relays now want a combined total of 120ma. The resistor will try to drop 12 volts, but we only have 9 volts on tap. So, current will have to drop and this will probably drop well below the point to energize three relays.
The answer is to use a resistor that can automatically adjust it's resistance to compensate for different relay current requirements. That sounds like a series voltage regulator. A three terminal 5 volt regulator is the perfect solution and only costs $2 at RadioShack.
This is how I'd do it... Remove the 100Ω resistor and the bottom 4700µF cap. Install a 7805 regulator, input connects to the positive of the cap, common (or reference) connects to the negative side of the cap, and the output becomes your +5VDC that connects to the relay coil. And now you don't have to be concerned with how many relays you try to energize simultaneously. (Within reason of course. That $2 7805 regulator is good for one amp, or 25 each 40ma relays, so don't exceed that. :wink: )
-
Sluckey,
THANKS as always for the reply! Any chance you can edit this schematic to give me an idea visually of what you're suggesting?
Is this the voltage regulator?
http://www.radioshack.com/product/index.jsp?productId=2062599 (http://www.radioshack.com/product/index.jsp?productId=2062599)
Doug,
OK, good without the extra 4700uf, I can make it smaller. I added back (into the layout) the 150R resistor to drop the voltage. But with Sluckey's method maybe that's not needed?
Can someone put a pair of eyes on this and see if we're getting closer?
With respect, Tubenit
-
+ 1 for what Sluckey told
an LM7805 is a simple/low-cost implementation
there are 7805 rated for 1A and other for 1.5A, a lot of paralleled relays
K
p.s.: here datasheet with spec and schematics
http://docs-europe.electrocomponents.com/webdocs/0d25/0900766b80d25b92.pdf (http://docs-europe.electrocomponents.com/webdocs/0d25/0900766b80d25b92.pdf)
-
Yes, that's the regulator. Doug carries it's cousin, the 7812, but that's for +12V. Here's the schematic for what I'm talking about...
-
You guys can hash out a multi relay power supply
Mine was only powering one relay in my amps
I have 7805's also, but I don't thnk I added them to the catalog
Using the 7805 is a much better idea
Don't forget that the 6.3 volt source is different on some trannies
You have no center tap using two 100 ohms
center tap to ground
champ style with one leg going to chassis
-
Tubenit just add a 100nf cap at the output of the regulator (the closest to the regulator you can) as to prevent oscillations
about relay connection don't you think it will be better to duplicate the turret of the contacts as to have an easier way of connection (one turret for the relay pin the other for the connection wire) ?
Ciao
Franco
-
This is how I'd do it... Remove the 100Ω resistor and the bottom 4700µF cap.
You forgot to take out the 180R. Your now using the 5v reg. inplace of it.
Tubenit just add a 100nf cap at the output of the regulator (the closest to the regulator you can) as to prevent oscillations.
Yep. You can go a lot bigger, KOC in TUT1 has a 2,200uF/10v on the input and 470uF/10v on the output. In another TUT book he has 1,000uF in both positions. And depending on how far away the input filter cap is from the reg. you my need to add a 2'nd small 1 directly to the input, again to prevent oscillations.
From page 23, figure 10 of the spec. sheet that K posted the link to;
2. CI is required if regulator is located an appreciable distance from power supply filter.
3. CO improves stability and transient response.
CI=0.33uF, CO=0.1uF. IIRC, distance is 2" or was it 4" at the max from the main/last B+ filter cap in the reg. PSU?
Brad :icon_biggrin:
Edit; K's link for reg. spec sheet;
http://docs-europe.electrocomponents.com/webdocs/0d25/0900766b80d25b92.pdf (http://docs-europe.electrocomponents.com/webdocs/0d25/0900766b80d25b92.pdf)
-
You forgot to take out the 180R.
What he said.
Don't forget that the 6.3 volt source is different on some trannies
Yes. Be careful here. If your filament winding has a CT connected to chassis, DO NOT CONNECT THE NEGATIVE SIDE OF THIS RELAY POWER SUPPLY TO CHASSIS! Doing so will poop the bridge or PT, maybe even both. Better to be safe and float this relay PS. There is no reason to connect the negative side to chassis. That means to also isolate any chassis connectors used to connect to a FS.
-
about relay connection don't you think it will be better to duplicate the turret of the contacts as to have an easier way of connection (one turret for the relay pin the other for the connection wire) ?
Doug uses (and sells) a socket for the relay so I don't think that will be a problem?
Brad :icon_biggrin:
-
May be I don't explained well what I mean
Quote from Doug
(1) I have added 4 lugs around the relay socket lugs so that I have better points to solder external wires to. Wires that lead to tube sockets, pots, etc are soldered to these extra lugs. It's much easier and better this way, it can be very difficult to solder to the lugs under the relay socket. Note that these extra lugs are jumpered under the board with short pieces of buss wire.
(http://www.el34world.com/projects/images/DSCN1796_small.JPG)
from this page
http://www.el34world.com/projects/relay_switch2.htm (http://www.el34world.com/projects/relay_switch2.htm)
Hope now you can understand what I was meaning
K
-
Anyone have experiance using a 6v DC wallwart for relay power supply?
-
May be I don't explained well what I mean
Quote from Doug
(1) I have added 4 lugs around the relay socket lugs so that I have better points to solder external wires to. Wires that lead to tube sockets, pots, etc are soldered to these extra lugs. It's much easier and better this way, it can be very difficult to solder to the lugs under the relay socket. Note that these extra lugs are jumpered under the board with short pieces of buss wire.
(http://www.el34world.com/projects/images/DSCN1796_small.JPG)
from this page
http://www.el34world.com/projects/relay_switch2.htm (http://www.el34world.com/projects/relay_switch2.htm)
Hope now you can understand what I was meaning. K
Ohh. I think I get it now. Maybe.
Brad :icon_biggrin:
-
OK, I think this is correct for 3 relays. I will revise this to have the 3 relays be operated by a 5pin DIN. Just don't have time now.
Can someone please confirm that it is correct? Thanks.
With respect, Tubenit
In addition to removing the resister wouldn't you have a cap before and after the regulator? I haven't built a rectified regulated power supply in 20 years. I used to build audio projects with + and - 15V regulated supplies. Start with a 24 Volt AC transformer. I don't remember any of the math. Right now trying to figure out if 5 volt AC can be turned into 5V regulated DC. I suspect it can.
-
In addition to removing the resister wouldn't you have a cap before and after the regulator?
Yes, look in reply #196, #197.
Brad :icon_biggrin:
-
Right now trying to figure out if 5 volt AC can be turned into 5V regulated DC. I suspect it can.
It can for very light, fairly constant loads. But 5VAC only gives 7 volt pulses to smooth out with the filter cap and then pass on to the regulator. Not enough headroom for good regulation. The regulator gets starved too easily.
-
I think you can use a voltage doubler on the 5v wind and get 14vdc.
Brad :icon_biggrin:
-
OK, I revised the layout board to foot switch wiring.
Is this CORRECT???
Don't forget that the 6.3 volt source is different on some trannies
You have no center tap using two 100 ohms
center tap to ground
champ style with one leg going to chassis
Be careful here. If your filament winding has a CT connected to chassis, DO NOT CONNECT THE NEGATIVE SIDE OF THIS RELAY POWER SUPPLY TO CHASSIS! Doing so will poop the bridge or PT, maybe even both. Better to be safe and float this relay PS. There is no reason to connect the negative side to chassis. That means to also isolate any chassis connectors used to connect to a FS.
I am not quite sure about the different 6.3v arrangements. It's late, I'll read that tomorrow and post any questions for clarification.
I hope this is helpful to someone. I've had a difficult time making sense of the relay stuff.
I am currently using one relay with an isolated ft switch jack. I have two 100 ohm resistors for the 6.3v ground.
Question: Would I still need an isolated jack using the 5 pin DIN?
With respect, Tubenit
Doug's 5 pages of relay explanations are here: http://www.el34world.com/projects/relay_switch.htm (http://www.el34world.com/projects/relay_switch.htm)
-
Right now trying to figure out if 5 volt AC can be turned into 5V regulated DC. I suspect it can.
It can for very light, fairly constant loads. But 5VAC only gives 7 volt pulses to smooth out with the filter cap and then pass on to the regulator. Not enough headroom for good regulation. The regulator gets starved too easily.
use 3VDC coil small signal relays. the light loading of the relay won't be much of burden if you use a good amount of capacitance and an adjustable VR such as the LM 317; better still the LDO LT-108x types. CPU 3.3V LDO regulators will work as well.
http://pewa.panasonic.com/assets/pcsd/catalog/ds-catalog.pdf (http://pewa.panasonic.com/assets/pcsd/catalog/ds-catalog.pdf) 3VDC relay - mouser stocks them.
--DL
-
Question: Would I still need an isolated jack using the 5 pin DIN?
No. You would only need to isolate a jack if the body of the jack is actually one of the electrical connections, such as the Switchcraft 12 phone jack that has the 'sleeve' connected to chassis unless you use fiber bushing washers. None of the DIN connecting pins actually touch the chassis when mounted, right? So the DIN is already isolated.
-
Anyone have experiance using a 6v DC wallwart for relay power supply?
this is a kit, but documented in a very good way, here you can find a lot of info about that
(http://dlnmh9ip6v2uc.cloudfront.net/tutorialimages/BreadboardPowerSupplyLanding/Breadboard_power_supply_kit_500.jpg)
http://www.homotix.it/catalogo/alimentatori-e-dc-dc-converter/breadboard-power-supply-5v-3-3v (http://www.homotix.it/catalogo/alimentatori-e-dc-dc-converter/breadboard-power-supply-5v-3-3v)
http://www.sparkfun.com/tutorials/297 (http://www.sparkfun.com/tutorials/297)
http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Kits/Breadboard%20Power%20Supply%20v10.pdf (http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Kits/Breadboard%20Power%20Supply%20v10.pdf)
http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Kits/Breadboard%20Power%20Supply%20v10.zip (http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Kits/Breadboard%20Power%20Supply%20v10.zip)
the schematic apply DummyLoad idea using an LM317
K
-
No. You would only need to isolate a jack if the body of the jack is actually one of the electrical connections, such as the Switchcraft 12 phone jack that has the 'sleeve' connected to chassis unless you use fiber bushing washers. None of the DIN connecting pins actually touch the chassis when mounted, right? So the DIN is already isolated.
Thanks for the answer, it is appreciated as always, my friend!
With respect, Tubenit
-
Question: Would I still need an isolated jack using the 5 pin DIN?
No........None of the DIN connecting pins actually touch the chassis when mounted, right? So the DIN is already isolated.
That's correct
-
OK, I revised the layout board to foot switch wiring.
Is this CORRECT???
No, I think where the LED is hooked up is backwards. Anode of the LED goes to + of relay and LED current limit 180R goes to ground.
And I think it would be easer to follow the din plugs pin layout if you would use pin 1 for switch 1, etc.....
Brad :think1:
-
Willabe,
There won't be an LED in the amp. It will only be in the footswitch box.
With respect, Tubenit
-
OK, here is the D'Mars (dual) OD Special Hoffman style layout board. You can see that his D'Mars board will work perfectly w/this.
Compare schematic with layout & check for errors.
The SCH version is here: http://www.el34world.com/Forum/index.php?topic=14302.0 (http://www.el34world.com/Forum/index.php?topic=14302.0)
A big thanks to Geezer for sharing his design with dual OD switching!
With respect, Tubenit
-
Willabe,
There won't be an LED in the amp. It will only be in the footswitch box.
Ok, but doesn't the LED's anode still have to be powered from the + side of the relay?
And in this verson of Dougs relay drawing you have the diode across the relay listed as the LED and no LED current limiting R.
Brad :think1:
-
I had in mind to use a 9volt battery inside the foot switch box if possible.
Well now that's a horse of another color than. :laugh:
Brad :icon_biggrin:
-
Right now trying to figure out if 5 volt AC can be turned into 5V regulated DC. I suspect it can.
It can for very light, fairly constant loads. But 5VAC only gives 7 volt pulses to smooth out with the filter cap and then pass on to the regulator. Not enough headroom for good regulation. The regulator gets starved too easily.
I could use a 7803 perhaps and use 3 volt relays.
-
Right now trying to figure out if 5 volt AC can be turned into 5V regulated DC. I suspect it can.
It can for very light, fairly constant loads. But 5VAC only gives 7 volt pulses to smooth out with the filter cap and then pass on to the regulator. Not enough headroom for good regulation. The regulator gets starved too easily.
use 3VDC coil small signal relays. the light loading of the relay won't be much of burden if you use a good amount of capacitance and an adjustable VR such as the LM 317; better still the LDO LT-108x types. CPU 3.3V LDO regulators will work as well.
http://pewa.panasonic.com/assets/pcsd/catalog/ds-catalog.pdf (http://pewa.panasonic.com/assets/pcsd/catalog/ds-catalog.pdf) 3VDC relay - mouser stocks them.
--DL
Thanks
-
CPU 3.3V LDO regulators will work as well.
Something like the LD1117 ?
http://it.rs-online.com/web/p/regolatori-di-tensione-low-dropout/6869782/ (http://it.rs-online.com/web/p/regolatori-di-tensione-low-dropout/6869782/)
K
-
Right now trying to figure out if 5 volt AC can be turned into 5V regulated DC. I suspect it can.
If you just want to energize some 5 volt relay coils, you don't need regulated voltage. Just put two or 3 diodes in series with the positive unregulated voltage and each diode will drop approx .7 volt. So, if you have unregulated 7 volts unloaded, two diodes would drop this to about 5.6v (unloaded). Probably just about right for a bank of 5V relays.
-
For any of you wanting a D'Mars OD Special Hoffman board, I just want to confirm that all of Doug's part fit great!
I finally got the mosfet installed & it's a perfect fit!
With respect, Tubenit
-
For those of you are willing to check the cap outer foil orientation to have a quieter D'Mars OD Special, ............ I am offering this information to consider.
with respect, Tubenit
-
Hi Tubenit
Your activity on sharing your project always increases in details
You are becoming always more refined :grin:
K
-
Looks good Jeff
-
For those of you are willing to check the cap outer foil orientation to have a quieter D'Mars OD Special, ............ I am offering this information to consider.
with respect, Tubenit
I did this when I built my twin but I didn't mark them. Good idea.
How hard is it to add reverb without messing up the balance of everything of else?
-
OK, here is the D'Mars (dual) OD Special Hoffman style layout board. You can see that his D'Mars board will work perfectly w/this.
Compare schematic with layout & check for errors.
The SCH version is here: http://www.el34world.com/Forum/index.php?topic=14302.0 (http://www.el34world.com/Forum/index.php?topic=14302.0)
A big thanks to Geezer for sharing his design with dual OD switching!
With respect, Tubenit
I was wondering if someone for educational purposes would draw the signal flow on the layout and schematic and perhaps mark up the gain and losses, frequencies affect and such. This would help me a ton, and I bet it would help a lot of others too. I really like the sound of this amp (still want to hear chords) and I love the layout, it's so clean.
-
How hard is it to add reverb without messing up the balance of everything of else?
Check this out> http://www.el34world.com/Forum/index.php?topic=9812.0 (http://www.el34world.com/Forum/index.php?topic=9812.0)
You could add a small "daughter" board for the reverb components so you could still use the Hoffman board layout
-
For those of you are willing to check the cap outer foil orientation to have a quieter D'Mars OD Special, ............ I am offering this information to consider.
with respect, Tubenit
I am trying to learn....
Comparing the board to the layout.
Is the 220R from 3 to 7 under the board?
Is the lead from 7 to power under the board?
I know you have mentioned the pigging back arrangement of caps on lug 5 and lug 19 (5 and 21 of the layout). Is there any issue with mixing electrolytic and those non-polarized (Xicon?) caps? Why would anyone use electrolytic caps at all?
The spacing of the components (especially the cap) directly to the right of E2 on the layout board seems squirrelly. Was Mr Hoffman using different components there?
The lug numbers do not match the layout. The layout seems to have skipped the number 4 when numbering. The layout numbers the center lug of the mosfet 8, while the board doesn't number the mosfet lug. Would it make sense to number all of the lugs on the layout we could do this ourselves, but it would be easier when discussing it, and place matching numbers on the schematic? Maybe these numbers can be in a different color than the tube pins, XLR pins, etc.
-
You could add a small "daughter" board for the reverb components so you could still use the Hoffman board layout
Absolutely could be done very easily. The reverb is essentially an amp in itself. You could make a very small board and mount it on the back panel or parallel it above the Hoffman board. Or you could use terminal strips. Easy enough to do. Put the dwell pot on the back or use a dwell resistor.
Regarding the questions ...............
I simply haven't soldered the 220R on yet. It's that simple. No issue mixing the Xicon & electrolytic or I would not have done it.
The spacing to the right of E2 is great. If it concerns you, ....then you can easily make your own board or spacing if needed, since I drew up a SCH layout that you can modify. Hoffman is a genius, IMO. No, same components.
OK the lug numbers don't match the layout. You're capable of relabeling them for yourself so they match.
My goal is to give you guys a foundation to build your own D'Mars OD Special.
Unless there is some really major mistake (that someone needs to let me know about), I will let you figure out the details. That is exactly what I had to do for myself, and frankly you have far more information to work with (given the info I provided) than I had starting from scratch. It has taken me about a yr to figure this amp out to design it, & hrs and hrs to provide this information freely to the forum.
Honestly, if someone is going to do a build like this & tweak it, they have to accept responsibility to figure some of this stuff out on their own. I say that with good will & IMO, that's just the way it is. And typically, if I have posted a question, it's after I've researched stuff out like crazy and was still uncertain.
:icon_biggrin:
With respect, Tubenit
-
You could add a small "daughter" board for the reverb components so you could still use the Hoffman board layout
Absolutely could be done very easily. The reverb is essentially an amp in itself. You could make a very small board and mount it on the back panel or parallel it above the Hoffman board. Or you could use terminal strips. Easy enough to do. Put the dwell pot on the back or use a dwell resistor.
Regarding the questions ...............
I simply haven't soldered the 220R on yet. It's that simple. No issue mixing the Xicon & electrolytic or I would not have done it.
The spacing to the right of E2 is great. If it concerns you, ....then you can easily make your own board or spacing if needed, since I drew up a SCH layout that you can modify. Hoffman is a genius, IMO. No, same components.
OK the lug numbers don't match the layout. You're capable of relabeling them for yourself so they match.
My goal is to give you guys a foundation to build your own D'Mars OD Special.
Unless there is some really major mistake (that someone needs to let me know about), I will let you figure out the details. That is exactly what I had to do for myself, and frankly you have far more information to work with (given the info I provided) than I had starting from scratch. It has taken me about a yr to figure this amp out to design it, & hrs and hrs to provide this information freely to the forum.
Honestly, if someone is going to do a build like this & tweak it, they have to accept responsibility to figure some of this stuff out on their own. I say that with good will & IMO, that's just the way it is. And typically, if I have posted a question, it's after I've researched stuff out like crazy and was still uncertain.
:icon_biggrin:
With respect, Tubenit
Hey man I'm just trying to learn how all this goes together. I haven't even grasped the signal flow as yet. Not planning to build it, more interested in how it works. That's why I stated trying to learn.... There was absolutely NO criticism. :worthy1:
I'm working on my own amp (and layout) and I am trying to figure out WHY certain components are layed out certain ways, pointing certain directions. This requires asking questions. Since you have a great sounding amp, it makes sense to question WHY it sounds so good. Can you dig it? :help:
-
I simply haven't soldered the 220R on yet. It's that simple.
Simple answer to a simple question
No issue mixing the Xicon & electrolytic or I would not have done it.
Why use electrolytic caps at all? Since they end up having to be replaced when they wear out/ leak? I thought it was related to the polarization.
The spacing to the right of E2 is great. If it concerns you, ....then you can easily make your own board or spacing if needed, since I drew up a SCH layout that you can modify. Hoffman is a genius, IMO. No, same components.
I asked this because it looks like the lugs are under the cap rather than on each end of it. Thought perhaps a different size cap was used.
OK the lug numbers don't match the layout. You're capable of relabeling them for yourself so they match.
I was thinking the amp layout and schematic with the labeling and notation could be a sticky or an article in how tube amps work and what parts do what. Obviously I can label it myself but that doesn't help a thousand other noobs (or me) learn how AC and DC audio circuits work.
No disputing the design is awesome and Dougs layout is genius, and the dual OD controls are way cool too. You spent a lot of time learning about how this stuff works so you could design your own. I'm trying to do the same thing. Having a full time job and no chance of ever retiring, and a family that demands much of my time off, I have to learn quick.
-
Having a full time job and no chance of ever retiring,
Welcome to the club! :laugh:
Talking about noobs and understanding things, in my own experience the simple circuits are the ones to learn on. My first build was Geezer's SoHo with the 2 relays, and quite honestly it was above me at that time, even though it's a pretty simple circuit for most guys on here. I had the dickens of a time getting the relays to work (Hoffman's law) and then when I did it hummed like hell because I didn't understand proper layout and grounding as well as I should have. I finally removed them and just used the one set of pots.
Tubenits latest amp looks like one I'd like to build someday, but not any day soon. I have more to learn before I attempt all those fricken switches and stuff. :icon_biggrin: And imvho, builds like that require more time than I've got at the present. I'd spend more time trying to remember where I'm at in the build than actually building it.
-
Anyone have experiance using a 6v DC wallwart for relay power supply?
And this is something I've wondered about myself. Has anyone done that?
-
Anyone have experiance using a 6v DC wallwart for relay power supply?
And this is something I've wondered about myself. Has anyone done that?
Why do that when you have a free power source in your amp from the heaters?
You can even send DC down a cord from the amp to a switch box to control LED's
-
Posted a sound clip > http://www.el34world.com/Forum/index.php?topic=14266.msg135711#msg135711 (http://www.el34world.com/Forum/index.php?topic=14266.msg135711#msg135711)
LOVE this amp!
G
-
Guys, check out Geezer's amp and playing ...............
http://soundcloud.com/dageezer/dumars-noodles1-0 (http://soundcloud.com/dageezer/dumars-noodles1-0)
My friend, that tone is as good as it gets, IMO!! I think your amp (& surely your playing too ........ sounds better than mine). Incredibly articulate, clear, touch sensitive tone.
Geezer's got more info on the link in the previous post.
THANKS so much for sharing it! with respect, Tubenit
-
Thanks T.....
in listening to the recording, it's hard to believe this is an approximately 10w amp! (the DuMars preamp into a 2x6AQ5A pair PP, cathode biased) It sounds & feels MUCH BIGGER!
The volume of the amp is quite low (you can easily hear me stepping on the footswitches & switching the guitar pickup selector @ about the same volume as the amp!)
Thanks for listening!
G
-
Hey Jeff , you're a good player, nice stuff. That 150 sure sounds good. Nice job!
oh, the amp don't sound bad either. :icon_biggrin:
-
Wow. Nice tone, even nicer playing!
-
Sounded real good, you covered a lot of area to let us get a good idea of how she sounds.
Thanks Bill
-
Yeah, it's sounds great
-
Hi Gents,
fantastic build and I aim to get mine started ASAP - @Geezer brilliant playing and tone
Q: is the BOM as posted by EL34 regarded as final ?
Attila
-
is the BOM as posted by EL34 regarded as final
The BOM that I posted (yesterday) in the SCH file noted EL34's revisions.
Please note that the BOM does not reflect the dual pots on the OD that Geezer uses nor does it reflect the relay switching. So if you use the dual pots and relay switching, then you'll need to add that to your parts list.
Having said that, I strongly encourage you to check the BOM against the schematic for accuracy. Won't take long to do and may save yourself some frustration in not having a part that you need.
With respect, Tubenit
-
Noted and thanks
-
I added several parts to stock this week that are used on this project
I have a post here with the list of new parts I stock
http://www.el34world.com/Forum/index.php?topic=14415.new#new (http://www.el34world.com/Forum/index.php?topic=14415.new#new)
-
E34,
THANKS for stocking the parts! This is a FUN amp to play and is very touch sensitive with a real sweet tone, IMO.
NOTE: I found using the Hoffman D'Mars board that I needed shielded wires going to the treble pot from the .002 and .02 caps on either side of the wiper. Something about crossing the B+ created some hum. I tended to use shielded wires on any long runs to the relays also.
Hoffman's board works great and is VERY sturdy in appearance.
With respect, Tubenit
-
Tubenit -
When you get a chance - could you please measure and post the voltages at PS taps C, D, & E of the D'Mars (dual) OD Special design. No hurry.
The soundfiles you kind gents have posted to date sound very much to my ear like those for a *Gkar Rumblier* if you catch my drift. Between this design and the HoSo - these are two of my dream amps that I never thought I could ever afford. My heartfelt thanks to both you and Geezer for all you have done for all of us!! :icon_biggrin:
-
Voltage chart was already in the SCH file. Doesn't matter if it's a dual or single OD controls as far as the B+ rail goes.
With respect, Tubenit
-
The soundfiles you kind gents have posted to date sound very much to my ear like those for a *Gkar Rumblier* if you catch my drift.
What the heck, are you afraid the lawsuit man is going to come after you or get you for saying a certain name that something just may happen to sound like!? Please...stop the nonsense. We're all grown ups here.
-
Gkar Rumblier
I am definately out of the loop
What exactly does that mean?
-
I think he means the "Carr Rambler"?
Brad :laugh:
-
I still have no idea
What is a Carr Rambler?
Not a Rambler car, I remember those
-
Sorry, Steve Carr amp company. The model is the Rambler. 2x6L6, 28w.
Read a couple of interviews with him in Tone Quest Report mag. years ago. Seemed like a nice guy, I seem to remember he lives down in N. Carolina?
Brad :icon_biggrin:
-
Just offering some info on a couple of "mods" that I've done.
NOTHING needs to be changed on the Hoffman style D'Mars turret board. All is good there.
mod 1: I wanted to see if I could create sort of a "chime" tone stack tone by separating the treble from bass pot but doing so between
the .02 cap and the bass pot. This is not really a PAB (preamp boost). It's more of a "voice" switch. Removing the bass pot
(sort of) gives a subtle tone change and makes the harmonics a little more vowel tone, IMO. Not a dramatic change, but a
useable one for me. I use this more than not. mini-toggle
mod 2: I paralleled a cathode cap on V1-3 and V3-3. This gives a mild gain boost on both clean and OD. Again it's subtle, but it gives
a "fatter" gain sound. I would describe it as fatter more than a volume boost relay & ft switch
mod 3: I paralleled a 100uf/100v cathode cap (with the original 100uf cathode cap). This tightens up the bass and seems to add a
little more harmonics in the mid range also. Having said that, the original 100uf cathode cap ALONE (not paralleled) has
more sustain and more "blooming" than the both paralleled. mini-toggle
NONE of these increased any idle/floor noise at all. Floor noise remained the same regardless of any of the switched positions.
NONE of this mods are a "must have", but I find them useful. They simply add some subtle tone changes that I like. None of these are a very dramatic tone change compared to the "midboost" ft switch which is a very audible increase in gain and mid tones.
I tried many more mods besides these and quickly removed them. These seem to be best of what I tried.
With respect, Tubenit
-
I still have no idea
What is a Carr Rambler?
Not a Rambler car, I remember those
Carr Amplifiers
433 W. Salisbury St.
Pittsboro, NC 27312
http://www.carramps.com/ (http://www.carramps.com/)
-
Cool looking amps!
-
You guys hit it perfectly!!
Sorry to be too mysterious. Did not want to get anyone in trouble of draw any flack toward the site is all. Probably much ado about nothing.
However if you get a chance to check out the Carr amp site, they have extensive MP3s of the Rambler. To my tin ear they sound at times very close to Geezers "noddling" in the D'Mars.
-
Just an update on this D'Mars OD Special.
Definitely, "my" favorite/best tone of any amp I've built so far. It has the best harmonics, sweetest very musical tone and smoothest sustain at this point. (The Tweed BluezMeister has comparable smooth OD ....... maybe?). The amp is very touch sensitive and at some level, reminds me of the HoSo56 (& a couple other builds) in that regard. Very articulate.
I've got the amp so quiet on the clean, that it is significantly quieter at idle than the original VibroChamp or Princeton Reverb I owned. And when you play a chord, it is waaaaay louder than either of those. In other words, with the pots set for a volume much greater than the VC or the PR, the amp is quieter at idle.
The quiet idle/most volume ratio is better on this amp than any I've built. Remember that's with 3 relay switching!
After building it and playing it over the last few wks. I went back in and moved a few wires around. Re-flowed a few solder joints & that helped the quietness.
This build is complicated enough that patience and persistence are major keys in making it a "WOW" sounding tone, IMO.
I also increased the cathode cap value on the power tubes to 200uf. I actually have a spdt mini-toggle that allows me to select from 100uf or parallel a 2nd 100uf. At 100uf, there is the most blooming and greatest sustain. At 200uf, there is a richer bass tone, clearer tone overall and perhaps sweeter harmonics. I play it with 200uf 90% of the time. IF I was only playing lead, I'd probably leave it on the 100uf because the blooming is a tad more pronounced.
The sustain and sweetness on the clean channel is remarkable, IMO. It has surprising sustain for such a clean and clear tone. Very musically sweet and rich tone. The clean channel with the midboost has more sustain than many of the early "higher gain" amps that I attempted. However, the tone is clean and clear without grit or distortion.
The OD has a nice "vowel tone" maintaining sweet harmonics like on the clean channel.
I also moved the relay power board on to the side of the amp by the PT. No problem with that. I previously had it mounted (inside the chassis of course) above the edge of the OT (which is on the other side of the chassis not chassis thru). Moving the relay board allowed me to move some of the 6.3v AC wires away from the OT wires. The result is the amp got somewhat quieter at idle and seems to have better harmonics. Unfortunately, I am not sure what increased the harmonics, because I moved some wires, reflowed solder joints moved the relay power board all at the same time. At any rate, having the relay power board on the side of the amp chassis is convenient, out of the way and defintely did NOT add any noise at all.
At this point, there is NO increase in noise (that I can tell) with the midboost engaged on clean. There still is some increase in noise with midboost on OD.
I am convinced that Doug's relay system is quieter than the previous W_____r relay board that I tried before. My guitar volume pot on "8" induces more noise than the amp has by itself. That's how quiet the amp is. In other words, Doug's relay system with 3 relays was quieter than the W_____ relay board with only 1 relay.
IF you look in the SCH file for the D'Mars ODS ...... I mentioned creating a sort of psuedo "chime" tone switch like I had on my TOS 2CF. While it's not exactly the same, it works and I like this tone the best. The chime is engaged almost 100% of the time. There is a schematic to show what I did with that. It's controlled by a mini-toggle and easy to wire up.
To sum up the highlights of the amp ................. it is the most musically sweet tone I've ever gotten, with the most tonal options (using the 3 ft switch pedal), & has the best quiet idle/loud volume ratio of any amp I've built.
I was initially concerned that an amp with this much wiring in this small of a chassis would be unbearable noisey. Not the case at all! I should add that my wiring is not that neat looking at all and probably wouldn't impress anyone ........ but the amp is still very quiet.
With all the info now on using Doug's relays, I wouldn't hesitate to recommend trying them on an amp that would be appropriate for relay switching. Once you've done it the first time, it makes sense and seems relatively simple to do.
Some things I tried that made no difference in reducing noise were the following : ground 6.3v 100 ohm resistors (artificial CT) to the power tube cathode, ground the PPIMV to the preamp buss wire, & ground the unused pins on the 5879 to the preamp buss wire.
With respect, Tubenit
-
Nice update
That's where I like to put the relay power supplies
On the side of the chassis far away from all the low signal wires
-
WOW :huh: :thumbsup:
You guys never cease to amaze me....that thing looks almost as good as it sounds!!!
Thank you for showing us the way and I can only look forward to tackling this build in the future :worthy1:
-
What chassis size would you recommend for this amp with the Hoffman style board?
-
I think I used a 20 x 8 x 2.5 .
IF I was getting someone to make one for me from scratch............. I'd like to try a 21" x 7" x 3".
with respect, Tubenit
-
OK, this post is (mostly) for Silvergun who has voiced "considering" the D'Mars ODS or TOS. I'm figuring out he likes to have some "gain" on hand (per his thread on the turbo wreck amp he's built)
:icon_biggrin:
In all fairness to disclosure, I did use a VERY VERY mild OD pedal boost on this with a Zenith Drive. The gain was around "1.5" and the level was around "3". That's it! The Zenith Drive does not have the same OD boost that a Tube Screamer does. It's much less than a TS. It's more of a "more" pedal, IMO.
I had to do that because I have a very difficult time getting a good OD tone recorded because my mic is always overdriven and it comes out too grainy. However, it should be noted that the PPIMV was set at less than "3" & IF I had the PPIMV set at 6 or above, it would easily duplicate the sustain & tone that the mild boost from the pedal provided.
Amp vol was "5", PPIMV less than "3", OD trim around "5", OD drive around "3" and OD level around "6". So what I am saying is that I can get even more gain/overdrive out of the amp if I want it. Midboost was on, but the PAB was NOT on. I can get more gain/OD with PAB on. I used a neck Cruiser (low output humbucking strat p.u.) and then the bridge Fast Track 1 on this clip.
I like this amp because I can get a very clear true clean tone all the way to a "cranked" tone like in this clip.
Excuse the repeated worn out guitar riffs. The sound clip is around 3 minute and that's probably 2.5 min too long.
Anyhow, check out the sustain on this. I can get almost any note to hold into feedback reasonably easily.
http://soundclick.com/share.cfm?id=11996721 (http://soundclick.com/share.cfm?id=11996721)
With respect, Tubenit
-
OK, this post is (mostly) for Silvergun who has voiced "considering" the D'Mars ODS or TOS. I'm figuring out he likes to have some "gain" on hand (per his thread on the turbo wreck amp he's built)
Thanks so much for taking the time to do that :thumbsup:........I can really hear the difference,,,and appreciate the clearness in the OD on that amp...
I'm still trying to dig through the mud on mine (and I love that), and if I could figure out how to work a mic and a 4 track,,,you'd hear the distortion monster that we have built over there.....
I'm ready to start thinking about another build, and I really do love the idea of built in gain (out the wazzu)....I have a TOS board, but I'm not dead set on that being next,,,,,,,I have also realized that BOARDS CHANGE :laugh:
I have followed the D'mars thread as an outsider, and appreciate the amount of effort that "you guys" have put into that amp......and it seems to me to be the culmination of a lot of previous work........the sustain and blooming is extremely atractive!!
I've been a fan of D'ble's stuff since I saw Robben Ford and Larry Carlton live (separately) sometime around 1994??,,,,so this IS the direction I want to go
I have always gone for a "smooth, liquid, searing, singing" lead tone,,,and one of my teachers even said I might want to try 2 OD units in series going into the front of an amp,,,,but to me it "feels" like I like the OD to happen sooner and later in the circuit (kinda pre AND post OD).......it really felt closer to home when we cascaded the last gain stage on my amp....
There are elements of each amp that I really enjoy, so I'll go back and listen to try to better describe those things that stand out to me on the TOS D'mars, AND TBM.........and I'm not afraid to build anything, now that I have seen what can be done to a ho-hum build....
I trust YOU....and if one of these amps stands out to you as what you would suggest, I am listening.....thank you for taking the time to care :notworthy:
.
-
You really got me thinkin.....
I loved the simple circuit build of the T-wreck,,,,and I've got all the parts to do the power section over, plus, I've got another OT...
What do you think about just taking the OD channel of the D'mars,,,,without the switching,,,effects loop,,,,clean channel considerations,,,,and just building it as another experimental platform for me to try to turbo charge, and expand on the theme?......
I'm sure I'm not alone in wondering what could be done to "supercharge" the D'ble topology.....(maybe it's already in there and you just haven't turn the controls up far enough yet....I always start with ALL the controls on 10 and then work backwards util my ears stop bleeding :l2:)
Sorry I'm always looking fore MORE gain OD :wink:...It's an illness,,,,,I know I'll grow up someday :rolleyes:
I'd rather have my amp do it than rely on a pedal (or 2)
EDIT***I went back and listened to the sound clip again,,,,and actually paid attention to the words on the page and noticed that the OD settings were less thn 50% !?!?!?.......that thing definitely has what I'm looking for......maybe I just want to build the single channel version for simplicity, and because I lack confidence for a more complicated build :dontknow:
-
T, First I'd like to say that I always like to hear your soundfiles and have many times. They're usually w/ background music and mostly playing leads which is okay but not covering chording/combined notes for definition, etc. Also they may have other things like small amounts of reverb, low setting of zenith drive (just mentioned), small amount of compression added into mix, etc. I know that these are for production value but I'd actually prefer to hear just the guitar plugged into the amp only, nothing more - and no song. This may seem like an odd request but for me, it's the only accurate & true way to hear clearly all the desctiptions you talk about it having.
For example, I'd like to to hear clean pristine chords, maybe some double stops, a few short lead or melody licks, let chords sustain for 5 or 10 seconds to hear them trail off occasionally. Maybe a jazz chord progression or country lick, to show it's clean side etc. Then in overdriven mode play some chords fast, then slow, sustain a few at different lengths, hold a single note for 20 seconds (if necessary) both with bending and w/out bending...holding...then add some finger vibrato, quick chording/slow chording, fast picking, light picking, heavy picking, double stops and bends, whatever you can show as far as diversity to help bring out the amp's descriptions. And most importantly, it's not about playing per-se, just demo'ing notes and chords to hear the true amp qualities be put on display. This won't be very good listening for the average person but for us striving to fully get a true measure & understanding of only the amp's tone and diversity, it's of more benefit to me (and others?) this way. If you could do this at some point it would be greatly appreciated, thanks!
-
Silvergun,
IF I had to guess, ........... I think you'd probably be the happiest with the original TOS design given the gain that you like. It will go to a very slight overdriven clean to a pretty intense overdriven OD. That may be the best choice for you? However, until I actually hear you play something .......... I may never be able to give you an educated guess?
:icon_biggrin:
Jojokeo,
Thanks for your suggestion. I will genuinely keep that in mind for the future. I used to do more of that. I wished I had 1/10th the talent of Geezer in demo-ing how an amp sounds without a backing track. I guess I've resorted to backing tracks because they're very quick and kind of fun to play along with.
With respect, Tubenit
-
However, until I actually hear you play something .......... I may never be able to give you an educated guess?
Thanks buddy,,,,I'll work on that......you deserve to hear what has happened on this end..
I've spent the mid morning listening to clips of both you and geezer demo'ing these amps,,,and they ALL sound great
Funny thing,,,,,if you go back 3 months and look at some of my first posts,,,,,I asked the same question about which amp to build,,,and even back then you said TOS...............................guess I really am hard of hearing :undecided:
Would you also lean towards the TOS because it's an easier build? :hijack1:
-
Would you also lean towards the TOS because it's an easier build?
No, I'd recommend something more complicated IF I thought it was a better fit for you. I am confident that you'd be able to handle it just fine.
My best guess is the original TOS is the "best fit" but I don't know cause I haven't heard you play? It is a very good just plug and play amp, IMO. Not much dialing in required.
IF you like a more midscooped sound you can do the TOS with a typical bass,mid & treble design very easily.
With respect, Tubenit
-
Sounded good Jeff great sustain I loved the tone , I have to finish this TOS Im working on to get to this one.
Bill
-
Just another update.
I have continued to experiment and tweak this amp after playing many hrs on it. Most tweaks I've tried since last update, I removed.
This last group of mods created a few tonal changes that I am keeping :
1) Amp is even quieter at idle & I did not think it was possible to get it quieter being a high gain amp. Amazingly quiet!!
I am thinking this is due to separating the mid and bass pots rather than the bass pot going into the mid pot. Not sure why that
would make a difference but it's defintely somewhat quieter (& I was happy with it even before this).
2) The amp is smoother when overdriven. It was very good before but would have a tad of grit if the mid pot was turned up. It
does not have that grit now. Again, I am thinking that when the bass pot went into the mid pot that this approach added some grit
when the midpot was around 6 or higher. Now it's just smoooooth!! No hash or grit.
3) I tried paralleling some different value pf caps with the 300p across the volume pot. Adding a 150p on a mini-toggle was a nice
mod. It tightened up the bass notes and made the tone a little fuller sounding. (no grit or hash added with this mod). I think this
would be a useful mod to dial in the 450p with single coil type pickups and the 300p with buckers. I am learning that on these
D-inspired amps that the cap values can create a "sweet & musical" spot in tone. In other words, 450p may sound fabulously
sweet and musical and full sounding. Less than that leaves it a little thinner and more than that it loses that "sweet spot". I find
similar sweet spots with coupling caps and it is worth the effort to slowly experiment in my opinon
4) The "traditional Dumblish PAB" simply does not work well on this CF tone stack arrangement. You can sort of create a "chime tone"
switch by miswiring the PAB, but it doesn't add a smooth overdriven boost. However, putting a 220k resistor on JUST the mid pot &
NOT the bass pot, did give me a very useable overdrive boost that is very very smooth sounding. I tried 82k to 470k values and
selected 220k. The traditional correctly wired PAB in the CF tone stack also sounded less musical and a little bit harsh & not as
smooth as lifting the mid pot with a switched resistor.
I should note that I had tried a 68k to ground PAB below the mid pot when the bass pot went into the mid pot. Did not like it at all.
It sounded too buzzy/gritty to me. Separating the mid and bass pot resolved this.
5) With the D'Mars on clean ................ there is NO unwanted noise increase when the PAB or midboost is engaged. I can't hear any
increase in idle/floor noise now. With the D'Mars on OD ............. the is very very little increase in idle/floor noise with PAB or
midboost engaged. In fact, I am very happy with the idle/floor noise when both PAB and midboost is engaged whether on clean
or OD.
6) The amp has less idle noise, more blooming and sustain & a smoother OD now. The harmonics, touch sensitivity and musical
sweetness has remained the same.
An added thought ................ I am wondering if the addition of the 500p across the outside lugs of the bass pot helps eliminate some
"hash" and adds smoothness instead?
Hope this may be of interest or useful to someone.
With respect, Tubenit
-
3) I tried paralleling some different value pf caps with the 300p across the volume pot. Adding a 150p on a mini-toggle was a nice
mod. It tightened up the bass notes and made the tone a little fuller sounding. (no grit or hash added with this mod). I think this
would be a useful mod to dial in the 450p with single coil type pickups and the 300p with buckers. I am learning that on these
D-inspired amps that the cap values can create a "sweet & musical" spot in tone. In other words, 450p may sound fabulously
sweet and musical and full sounding. Less than that leaves it a little thinner and more than that it loses that "sweet spot". I find
similar sweet spots with coupling caps and it is worth the effort to slowly experiment in my opinon
T- I've had experiences where I couldn't find a happy place with a treble cap by itself no matter the value, then found success w/ a resistor in series. Yes, it takes time to find the right combo but as you say it's worth it when you do. For simplicity sakes, start w/ a 47k & 500p. Doing this gives an "in between" effect from all (cap only) or nothing (no cap at all). It also helps minimize the shelving effect (bright/brittleness) in really low settings of the pot rotation.
-
cap by itself no matter the value, then found success w/ a resistor in series
Yes, that is a great approach. I used that on my guitar volumes.
With respect, Tubenit