Fuzz control capacitor values

[MBFX]

I was playing around with a Si Fuzz Face this weekend on the breadboard, and it just wasn't doing enough. Voltages were all where they should have been, but the fuzz died out too fast and high notes were nearly clean. The decay would fizzle out, too. I tried a bunch of different transistors with the same result every time. On a lark I replaced my fuzz control capacitor with a 100uf, and all of a sudden the problem was fixed. I'm curious why the called-for 20uf didn't work in this case, and I needed such a huge value.

 

[Big Monk]

I was playing around with a Si Fuzz Face this weekend on the breadboard, and it just wasn't doing enough. Voltages were all where they should have been, but the fuzz died out too fast and high notes were nearly clean. The decay would fizzle out, too. I tried a bunch of different transistors with the same result every time. On a lark I replaced my fuzz control capacitor with a 100uf, and all of a sudden the problem was fixed. I'm curious why the called-for 20uf didn't work in this case, and I needed such a huge value.

What were your collector voltages?

 

[MBFX]

What were your collector voltages?

Q1 = +1.15VDC
Q2 = +4.71VDC

I did a lot of searching, and it seems like that's pretty typical for a Si Fuzz Face. Please let me know if you agree!

 

[Big Monk]

Sounds like a common, unintentional breadboarding error.

Try the 22u cap again and make sure your wires are properly seated.

 

[MBFX]

Sounds like a common, unintentional breadboarding error.

Try the 22u cap again and make sure your wires are properly seated.

I tried it a bunch of times, including with the circuit live, to hear the difference. I also tried some very low cap values to see if it made the problem worse. Everything did what I expected it to - 10nf was choked and barely passed sound, 0.1uf slightly better, 10uf low notes fuzzy, 22uf works but not great, 100uf hooray big fuzz. To try and simplify things, I replaced the fuzz pot with a fixed 1K resistor. Any ideas?

EDIT: not sure if it matters like it can with other components, but the transistors are at least 30 years old

 

[Big Monk]

I tried it a bunch of times, including with the circuit live, to hear the difference. I also tried some very low cap values to see if it made the problem worse. Everything did what I expected it to - 10nf was choked and barely passed sound, 0.1uf slightly better, 10uf low notes fuzzy, 22uf works but not great, 100uf hooray big fuzz. To try and simplify things, I replaced the fuzz pot with a fixed 1K resistor. Any ideas?

Do you have a full schematic?

 

[MBFX]

Yep, the Electrosmash one. Please ignore the polarity; I wired it NPN because it's a Si Face

 

[Big Monk]

Is there a difference in the lead size for the capacitors?

 

[MBFX]

Lead size as in diameter, no. Lead size as in length, yes. The 100uf has trimmed leads because I was using it for something else. The 20uf only has the longer leg clipped to make it the same length as the shorter leg.