intertesting oscillation fix

[tcobretti]

Maybe everybody knows this but me, but I figured I'd post my findings for posterity.

My si tone bender mk II was oscillating at full fuzz.  I tried reorganizing the layout, shielded wire and a small cap after the input cap, all tricks I had learned from here, none of which helped.  Finally defeated, I turned the fuzz pot down to where the oscillation stopped and measured about 300 ohms, so I dug up a 330 ohm resistor and stuck it in there - no surprise, the oscillation stopped.  But then I figured I wanted the smallest resistor I could use so as to maximize the gain from my pedal, so I started trying smaller and smaller resistors.  Finally I stopped at 22 ohms, because it sounded lke max fuzz without the resistor, but with no oscillation.  As a futher experiment, I did try a jumper instead of a resistor and the oscillation returned.

Long story short, it seems that a very small resistor (much smaller than measuring the pot would indicate to be necessary) before the gain control can solve oscillation on a fuzz pedal.  In my case the resistor was so small as to have an undetectible effect on the fuzz besides eliminating the oscillation.

Anybody have any science to back this up or was I just lucky?