Chirping Big Muff

[malaphone]

Hi - I'm a new member. This forum is great! I have built the Gran Mango (Big Muff) circuit maybe half-a-dozen times, and they've always turned out great. I just built another one, and it has a funny oscillating sound when I turn the tone knob all the way down. The pitch of the oscillatiing sound seems to be controlled by the sustain knob. It distorts nicely, good volume, just noisier and "chirpy". The only thing I did different, was use ceramic capacitors instead of mica for the the 500pfds. After reading the FAQs, I think that might be a red herring. Has anyone else encountered this, or have an idea where I may have gone wrong?

Thanks in advance!
M

[R.G.]

Good insight - the ceramic versus mica is a red herring.

You probably have some problem with the power supply or ground. The chirping oscillation in a known-good circuit is an indication of feedback through the power supply. Could be wiring or layout if you did your own board.

[malaphone]

Hey RG,

Thanks for the tip. It was feedback through the power. I found the positive from the LED was making contact with the board :oops: . It was really unnoticable, and probably would've taken forever to find if I hadn't known to focus on the PS. Thanks again!

M