Fuzz XIII Squealing with gain up

[HamishR]

Just built a Fuzz XIII (Basic Audio Lucky Number) and it's great! Really like it. But when I push gain over around 2-3.00 I get that familiar hiss/squeal thing.

The only thing I did which isn't stock was use BC550B transistors instead of BC549C. Surely they would be close enough?

Oh, and it's a Vero build because I wanted the Fat knob to be under the Volume pot - maybe the layout is causing an oscillation? I have changed the layout but both versions I have built squeal much the same.

Could it simply be a matter of sticking a small cap over some transistor pins?

Thanks!

 

[music6000]

Have you tried reversing Electrolytic + to Fat 2?

 

[HamishR]

I was wondering about that - it does seem odd, doesn't it? I wouldn't have thought it would cause squealing though. Worth a try, and I probably should have just built it that way!

 

[HamishR]

Nope, turning the 10µF Fat cap made zero difference. Possibly a slightly different tone to the hiss/squeal but that's it!

 

[music6000]

Can we see a picture of the Board?

 

[HamishR]

I doubt it would tell you anything. I tried two substantially different layouts and both have the same symptoms.

 

[music6000]

Without seeing the components, it's pointless to know why your pedal may be faulty.
You have 1k's,10k's, 100k's, 1M .
If I got a dollar for everytime I spot or have seen a wrong Multiplier 4th Band on this forum, I would be buying a custom shop tele!