18W Tremolo TMB Xtra Gain build

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Re: 18W Tremolo TMB Xtra Gain build

Post by JMPGuitars »

I'm probably going to make a Tremolo TMB Xtra...and because I'm cuckoo, I'm going to fit it on a much smaller PCB.
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Re: 18W Tremolo TMB Xtra Gain build

Post by Bieworm »

JMPGuitars wrote:
Mon 02/21/22 4:42 pm
I'm probably going to make a Tremolo TMB Xtra...and because I'm cuckoo, I'm going to fit it on a much smaller PCB.
This one is pretty Xtra!! Going to have to swap the 1M Xtra gain pot to 500k or even 250.. it oscillates after 9.00
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Re: 18W Tremolo TMB Xtra Gain build

Post by JMPGuitars »

Bieworm wrote:
Mon 02/21/22 5:03 pm
JMPGuitars wrote:
Mon 02/21/22 4:42 pm
I'm probably going to make a Tremolo TMB Xtra...and because I'm cuckoo, I'm going to fit it on a much smaller PCB.
This one is pretty Xtra!! Going to have to swap the 1M Xtra gain pot to 500k or even 250.. it oscillates after 9.00
That doesn't surprise me. I think doing the Xtra mod OR the 1M pot would probably work, but both is a little cuckoo. The point of it being 250K in the first place was to avoid driving into blocking distortion.
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Re: 18W Tremolo TMB Xtra Gain build

Post by Bieworm »

JMPGuitars wrote:
Mon 02/21/22 9:58 pm
Bieworm wrote:
Mon 02/21/22 5:03 pm
JMPGuitars wrote:
Mon 02/21/22 4:42 pm
I'm probably going to make a Tremolo TMB Xtra...and because I'm cuckoo, I'm going to fit it on a much smaller PCB.
This one is pretty Xtra!! Going to have to swap the 1M Xtra gain pot to 500k or even 250.. it oscillates after 9.00
That doesn't surprise me. I think doing the Xtra mod OR the 1M pot would probably work, but both is a little cuckoo. The point of it being 250K in the first place was to avoid driving into blocking distortion.
I can understand why. But although the 250k in your Tremolo TMB has a better sweep I like the 500k in the prototype better. It adds more than just some gain. The tone is somewhat sweeter. In this build I copied that.
It's really nice! The 2-9-18W switch and the gain boost switch are really making it very versatile
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Re: 18W Tremolo TMB Xtra Gain build

Post by Bieworm »

Ok did some tweaks since the Xtra gain knob is giving oscillation/blocking distortion when dialed up too high.
on the schematic I initially had (see numbers)

1. nothing
2. pot A1M
3. 33k

I tried a 250k pot, but it still gave me much blocking distortion when dimed, so I added a 470k resistor in series between the .022uf cap an the pot.

1. 470k resistor
2. pot A250k
3. 33k

I still have some of the ugliness left.. here's things I could try:

A. put in a 100k of 50k pot?
B. put a 270k resistor in parallel with the pot?
C. put an even larger resistor in series instead of the 470k?
D. put an extra voltage divider before the 470k / A250k divider? This seems silly
E. is upping the 33k grid stopper going to do anything but darken things?
schema 18W cascade reverb tremolo execution rev01.png
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Re: 18W Tremolo TMB Xtra Gain build

Post by JMPGuitars »

Your schematic is showing 470K grid leaks on the power tubes. Switch those to 220K and see how it sounds.
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Re: 18W Tremolo TMB Xtra Gain build

Post by Bieworm »

JMPGuitars wrote:
Thu 02/24/22 11:25 am
Your schematic is showing 470K grid leaks on the power tubes. Switch those to 220K and see how it sounds.
Thanks Josh... but I would like to maintain the Tremolo TMB sound when in parallel mode.
Will give it a shot anyway.. although it's a vox thang 😃
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Re: 18W Tremolo TMB Xtra Gain build

Post by Bieworm »

Sorry Josh.. but I tried a 100k Xtra Gain pot and it's spot on! Really nice crunch now.. even on full on dial. This is with the A500k Gain pot at 3 o'clock and the A100k Xtra Gain pot at 2 o'clock... rock on!!!

https://www.dropbox.com/s/ibba6h3d4iqr1 ... t.m4a?dl=0
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Re: 18W Tremolo TMB Xtra Gain build

Post by JMPGuitars »

Bieworm wrote:
Thu 02/24/22 2:13 pm
Sorry Josh.. but I tried a 100k Xtra Gain pot and it's spot on! Really nice crunch now.. even on full on dial. This is with the A500k Gain pot at 3 o'clock and the A100k Xtra Gain pot at 2 o'clock... rock on!!!

https://www.dropbox.com/s/ibba6h3d4iqr1 ... t.m4a?dl=0
lol, no need to apologize. You can compensate for the gain issue in the preamp (which you did) or you can compensate in the power amp (or both). You may find you like it better one way or another, but you'll never know if you don't try. 😉
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Re: 18W Tremolo TMB Xtra Gain build

Post by Bieworm »

JMPGuitars wrote:
Thu 02/24/22 4:32 pm
Bieworm wrote:
Thu 02/24/22 2:13 pm
Sorry Josh.. but I tried a 100k Xtra Gain pot and it's spot on! Really nice crunch now.. even on full on dial. This is with the A500k Gain pot at 3 o'clock and the A100k Xtra Gain pot at 2 o'clock... rock on!!!

https://www.dropbox.com/s/ibba6h3d4iqr1 ... t.m4a?dl=0
lol, no need to apologize. You can compensate for the gain issue in the preamp (which you did) or you can compensate in the power amp (or both). You may find you like it better one way or another, but you'll never know if you don't try. 😉
you're right! it's pretty easy to try when I parallel another 470k resistor with the EL84 grid leak resistors..
thanks for your input!
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Re: 18W Tremolo TMB Xtra Gain build

Post by JMPGuitars »

Bieworm wrote:
Fri 02/25/22 4:39 am
you're right! it's pretty easy to try when I parallel another 470k resistor with the EL84 grid leak resistors..
thanks for your input!
Another thing you can do is the stupid simple master volume. Play around, and when you're done, measure the resistance you like the best at the grid leaks.
Stupid Simple Master Volume.jpg
Obviously if you drop the volume with that too much, you lose power amp distortion.

Thanks,
Josh
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