18 Watt Trem TMB: Gain Pot bleeding through

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Re: 18 Watt Trem TMB: Gain Pot bleeding through

Post by JMPGuitars »

That sounds excellent! Well done.
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Re: 18 Watt Trem TMB: Gain Pot bleeding through

Post by rexindigo »

Thank You Josh. Now that i had the amp in rehearsal with the band, i think i want it a bit mor gainy...
So maybe ill go back to the resistor on the gain pot and the original pot values.
Maybe ill also try out to omit the sag resistor
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Re: 18 Watt Trem TMB: Gain Pot bleeding through

Post by Bieworm »

rexindigo wrote:
Wed 10/18/23 12:28 am
Thank You Josh. Now that i had the amp in rehearsal with the band, i think i want it a bit mor gainy...
So maybe ill go back to the resistor on the gain pot and the original pot values.
Maybe ill also try out to omit the sag resistor
You won't get a lot more gain that way, believe me..
Maybe what you 'could' do is to put the 2 parallel triodes from the 2nd amplification stage in series. Josh has designed something like that in the Tremolo TMB Extra series. But he didn't share those docs yet.
I have done this too with one of my builds.
If you want more info you can always scroll through this thread:viewtopic.php?p=252636&hilit=extra+gain#p252636
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Re: 18 Watt Trem TMB: Gain Pot bleeding through

Post by JMPGuitars »

Bieworm wrote:
Wed 10/18/23 3:57 am
You won't get a lot more gain that way, believe me..
Maybe what you 'could' do is to put the 2 parallel triodes from the 2nd amplification stage in series. Josh has designed something like that in the Tremolo TMB Extra series. But he didn't share those docs yet.
I have done this too with one of my builds.
If you want more info you can always scroll through this thread:viewtopic.php?p=252636&hilit=extra+gain#p252636
The mod in the Tremolo TMB Xtra is to add a Parallel/Cascade switch. I will be sharing those docs soon as the circuit is tested and sounds awesome.

He said he "changed the preamp tubes to lower gain" - if he's not using 12AX7 or equivalents, that would be why there isn't enough gain.
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Re: 18 Watt Trem TMB: Gain Pot bleeding through

Post by Bieworm »

JMPGuitars wrote:
Wed 10/18/23 10:51 am
Bieworm wrote:
Wed 10/18/23 3:57 am
You won't get a lot more gain that way, believe me..
Maybe what you 'could' do is to put the 2 parallel triodes from the 2nd amplification stage in series. Josh has designed something like that in the Tremolo TMB Extra series. But he didn't share those docs yet.
I have done this too with one of my builds.
If you want more info you can always scroll through this thread:viewtopic.php?p=252636&hilit=extra+gain#p252636
Parallel triodes have a fatter sound, not higher gain. You mean cascade. The mod in the Tremolo TMB Xtra is to add a Parallel/Cascade switch. I will be sharing those docs soon as the circuit is tested and sounds awesome.

He said he "changed the preamp tubes to lower gain" - if he's not using 12AX7 or equivalents, that would be why there isn't enough gain.
I thought triodes in series was the same as cascaded. At least, that’s what I meant.
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Re: 18 Watt Trem TMB: Gain Pot bleeding through

Post by JMPGuitars »

Bieworm wrote:
Wed 10/18/23 11:55 am
I thought triodes in series was the same as cascaded. At least, that’s what I meant.
That's correct. I guess I wasn't awake yet and didn't read the whole thing. I corrected it. 🙄🤣
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Re: 18 Watt Trem TMB: Gain Pot bleeding through

Post by rexindigo »

Hi, just a short update: i have removed the DC heater circuit i bought, because it was getting to hot.
Removed the sag resistor, removed the resistor to ground on the gain pot, changed the slope resitor from 56k to 68 k, because i want it to be more sparkly...
tubes are in the moment: first-> 12AX7, second->12AX7, PI-> 12AT7
its more gainy now, but i cant test because its to late now
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Re: 18 Watt Trem TMB: Gain Pot bleeding through

Post by rexindigo »

After rehearsal on tuesday i was still not completely happy. Added switchable negative feedback (from the 36Watt TMB Layout by Hall and Ankelei ) and this is it! like it very much now. Can anyone point me how to wire NFB permanently without the switch?
I just cant get my head around it.... Thank You in Advance
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Re: 18 Watt Trem TMB: Gain Pot bleeding through

Post by rexindigo »

I have fixed it, so the changes to the original schematic so far are:
Removed the sag resistor, removed the resistor to ground on the gain pot, changed the slope resitor from 56k to 68 k, added the FX loop, added a negative feedback with a 39k resistor from the 36 Watter schematics.
the cool thing about homebrew amps is.... you can mod it all the time ;-)
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