Fuzz Face Feedback

[skypn]

I modded a FF with a bigger input cap for Bass. I loaned it to a 6 string friend of mine who wanted to check it out. He found he got a hint of feedback if the gain went past 1/2 way.
Here is the schematic:
https://ibb.co/6FJw2fJ
Do you guys think maybe it's transistor bias? I'm still kinda a newbie, so I'm not sure where is start.
TIA

[jwin615]

Possibly being obtuse here... Likely just their rig, if I had to guess.  Stand further from the amp and point the guitar away from it.
If it goes away, it's just normal feedback. The added low frequency capability may play a bit of a factor as well. Especially with single coils in a small room environment.
Now, if they turn their volume pot down and it still happens, then we have a bigger problem.
What's your bias voltage?
Or is it oscillation, which is a different can of worms.

[skypn]

Hmmm. That's a tad to consider. I had thought it may be the input cap. As far as if its in his rig? He has since given the pedal back, so...
I don't hear any feed back, but again, I testing using a Bass, or a 6. both played through a 25w Bass amp.

OK, let me hijack my own thread: What effect on the sound does the bias on Q2 have?

I can start a new thread, if I should.
TIA