Electronics guys, Why the hell is my pedal so damn noisy?


Den Mørke Natt
Oct 22, 2008
Sacramento, CA
I thought I had troubleshooting down pretty good, until this happened. My SD-1 lately has been noisy as hell, so I decided to pull the thing apart and testing it to make sure everything is working normally. I rule out my guitar and input signal, discovering that the signal is begin shunted to ground when the volume is all the way down. Without an input cable connected to anything, the noise was still there. From the schematics, the output cannot be shunted to ground, so the amp is going to take in any noise that the pedal is amplifying, but if the input of the pedal is shunted because there is no cable, then the only noise there should be is resistor noise mostly, but is sounds like I have a ground loop issue.

When everything is disconnected from the jack with the amp plugged into it when the signal is shunted to the ground of the amp, it gets quiet, only amp noise, as if there was no cable even plugged into the amp. Disconnect the jack from everything again, connect only the ground of the pedal to the jack, and connect the amp cable into the pedal, noise is back. What is even more strange is that as soon as you shunt the signal to ground (having the ground of the pedal connected to the ground of the amp amp) or connect the pedal's output signal to the jack the noise gets worse. When its only the grounds that are connected the noise is a 60Hz with a whooshing sound, then the signal is shunted to ground, its a distorted 120Hz signal that although is more quiet, is more noticeable.

Only thing I can think of is to disconnect the ground of the pedal from the chassis. That would be hard because the jacks connect up to the chassis so it would be hard to do unless i disconnected the ground of the DC supply from the pedal entirely. I am pretty sure that would work, I think.