Nasty oscillations on fuzz in 2 circuit pedal



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Nasty oscillations on fuzz in 2 circuit pedal

Postby Ben79 » Mon Aug 13, 2018 12:46 pm

Sorry for the age old question but I couldn't find an answer for this elsewhere....

Built a Repeat Percussion and Si Fuzz Face in one enclosure. Both have a 100ohm then a 0.1uf cap to ground from the main +9V. The fuzz is making nasty oscillation noise and does not sound good.

What should I try? A biggish cap to ground before the 100ohm?

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Re: Nasty oscillations on fuzz in 2 circuit pedal

Postby crochambeau » Mon Aug 13, 2018 3:36 pm

Have you messed with the gain of the first stage at all? Decreasing the collector resistor and/or inserting resistance at the emitter would be my first step.

I guess I didn't ask if that circuit sounded good before combination with the other circuit....

How is that done, exactly?
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Re: Nasty oscillations on fuzz in 2 circuit pedal

Postby Ben79 » Mon Aug 20, 2018 2:30 pm

....by testing it with the power to the other circuit disconnected!

Did that and it still oscillated - ergo my hasty presumption that it was a powering issue to do with the parallel circuit was wrong.

Noticed that one if the trimmers wasn't doing anything, and then saw why, big old solder bridge the other side! Fixed that, oscillation gone and the pedal sounds great.

I wonder sometimes when I build pedals and it goes wrong if it's really technical assistance I need or some kind of counselling.

Thanks Curt! As usual.
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