Two Sticks of Derm Fuzz gain control
- Thread starter HamishR
- Start date
BuddytheReow
Breadboard Baker
If I had to guess I’d say change R4 or R8 to a pot. Perhaps a dual pot?
mdc
Well-known member
One option:
Pull R5 and C5.
Use a continuity tester to figure out which R5 pad connects to C4, and which connects to ground.
Connect Lug 3 of a 100K pot to C4 via the appropriate R5 pad.
Connect Lug 1 of the pot to ground via the other R5 pad.
Use a continuity tester to figure out which C5 pad connects to R5 and which connects to Q2-base/etc.
Connect Lug 2 of the pot to one side of a 100n cap
Connect the other side of the 100n cap to Q2-base/etc via the appropriate C5 pad.
This should give you a gain control between the two stages.
Another (easier?) option would be to just add a pot between the footswitch and the PCB.
Lug 3 to the footswitch
Lug 1 to ground
Lug 2 to the PCB
You might have to try a few different values in case there's any weird loading or anything happening, or you might want to add a treble bypass cap between lugs 2 and 3 to retain a bit more high end as you roll back the gain.
Pull R5 and C5.
Use a continuity tester to figure out which R5 pad connects to C4, and which connects to ground.
Connect Lug 3 of a 100K pot to C4 via the appropriate R5 pad.
Connect Lug 1 of the pot to ground via the other R5 pad.
Use a continuity tester to figure out which C5 pad connects to R5 and which connects to Q2-base/etc.
Connect Lug 2 of the pot to one side of a 100n cap
Connect the other side of the 100n cap to Q2-base/etc via the appropriate C5 pad.
This should give you a gain control between the two stages.
Another (easier?) option would be to just add a pot between the footswitch and the PCB.
Lug 3 to the footswitch
Lug 1 to ground
Lug 2 to the PCB
You might have to try a few different values in case there's any weird loading or anything happening, or you might want to add a treble bypass cap between lugs 2 and 3 to retain a bit more high end as you roll back the gain.
Sturdag Lagernathy
Well-known member
I'd go with a B1M pot between FS and the pcb input..
ColorMeBaddFann
Member
Following here for ideas. I had purchased a pre-drilled 1590b for another one-knob project that also included an additional hole on the face for a spdt/dpdt. That idea sort of fizzled, so picked up a TSoDF pcb to build out a doom-y type fuzz.
But what to do with that other spot? Any good suggestions for cap changes that would maybe increase or cut bass frequencies? Or do something else that might be cool? I'm still in the "paint by numbers" stage of pedal assembly, and I've only colored outside the lines in a few instances. Super appreciative of any interesting options!
But what to do with that other spot? Any good suggestions for cap changes that would maybe increase or cut bass frequencies? Or do something else that might be cool? I'm still in the "paint by numbers" stage of pedal assembly, and I've only colored outside the lines in a few instances. Super appreciative of any interesting options!
For bass modification, C1, C5 and C7 all filter bass.
You could double C5 and C7 to 200/220n then switch C1 for more/less filtering at the input.
Or do a filter cap pot where you blend between 2 filter caps with a low value linear pot. If you try that, experiment on the breadboard. Try values that are at least 10x each other, 47n and 470n or even more 20n and 1u.
I'm toying with this on a muff build but wasn't happy with my values and haven't circled back to it. You need to exaggerate the values as they'll always be in some amount of parallel.
Switching is much simpler. Or even a rotary.
Here's one of many threads on input cap blending
Some over at madbean as well
Good luck!
ColorMeBaddFann
Member
Thanks again! I'll have at this once my next parts order arrives... forgot I'm all out of 1/4" jacks... d'oh
Feral Feline
Well-known member
2N3904 is spec'd.
"The B-E junction saturation voltage is typically 0.65V but can be as high as 0.95V. The Gain (Hfe) in combination with the maximum C-E Current is what you want to look at. unfortunately the Hfe can typically range from 100 to 400 and vary wildly from transistor to transistor."
—
2N3904 input voltage range
hello, i have question of whether the input to 2n3904 can be like 2V? is there some input voltage range for 2n3904? thank you
www.electro-tech-online.com
Typically about 250hFE, I guess.
Try also...
2N2222
2N3053
2N3392
2N4401 (a bit hotter)
2N5172
2N5550 /2N5551
BC338 (also more oomph)
BC546B
PN2222A
Check the datasheets for whatever you're trying, to get the correct pinout and hFE range.
Cybercow
Well-known member
Got my first (of three) "Two Sticks of Derm" builds done this morning and tested it with the stock 2N3904s. Awesome! I also tried a few other standard jellybean silicon BJTs and they all seem to work quite well in this circuit.
Then I thought, what about NPN Germaniums? With R2 & R6 replaced with 100K trimpots, I slipped in two NOS Ge NPN NTE103A (2SK3835) BJTs (hfe @ ~200) at Q1 & Q2 with a NOS Ge Mullard CV7112 (OC140) at Q3. At first it was very gated, but then I turned the trimpot at R2 down to ~8K2, (setting the trimpot at R6 at ~33K), and it came to life beautifully! I noticed that with the Ge BJTs, the attack transient is much sharper and extremely defined - adding a nice nuance to the fuzz. I'm considering replacing the two 4K7 resistors at R4 & R7 with trimpots to see how well the "Fuzz" aspect can be controlled. A more detailed, stand-alone post (with pics) is forthecoming.
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Many__Of__Horror
Active member
Did you end up with a good solution for this one @HamishR ? I need to do this as it is too loud to get the full doom.
