How to get rid of this high pitch oscillation in a fuzz face?

[henryd]

Hey guys, I built a silicon fuzz face with nos components on a pigeon fx pcb trying to replicate it as close as possible to an original. I got it to work but there is this high pitch sizzle when all controls are on max. I breadboarded the exact circuit out with similar nos components, and there is no high pitch noise on that at all. I did swap out the tfk bc108c transistors for others on the pigeon pcb but it didn't change it. Is there something that I'm missing? all of the resistors look to be close enough values on my multimeter.

The first half is the pigeon pcb with the noise and second half is the breadboard which sounds find:
Link to soundcloud

 

[henryd]

Looks like the major difference between the vintage board and the Pigeon FX board is:

View attachment 62401

One way to test this would be to set the breadboard up just like the PCB and see if the noise persists with components and wires in the same proximity as the circuit board.


EDIT: Correction - It looks like you have the iss2 NPN Silicon board, which would not match the iss1 board I show below it. That's my bad.

I have to say that in light of that, board error seems unlikely, although Fuzz Faces are super noisy without deliberate mitigation. Wish I could help more.

I really appreciate all your help with this fuzz face. I still have other components for other fuzz faces, so I ordered two more pcb's and am going to build a second with different parts to see if this one just happens to be a combination of old components or the board. If that doesn't fix it then it must just be the wires not blocking noise or bad solder joints. I'll get it to work soon enough!

 

[cdwillis]

If the transistors have a lot of gain you can put a small (47 ohm or 100 ohm) resistor between ground and the electrolytic cap hooked to the fuzz control to stop the oscillation.

 

[analogdevice]

It's worth noting that breadboards have a stray capacitance between rows which can make tracking down oscillations in fuzz circuits unreliable. It sounds like the common high frequency oscillation issue that occurs when using transistors with too much gain in the stock circuit. I would try the cap from collector to base as mentioned earlier or seek out some lower gain transistors.