Guitar hum eliminated by overdrive pedal


Jun 19, 2011
I noticed that if I plug my guitar straight into my interface and load up a high gain amp sim, I can hear that electrical buzzing when not playing.

But if I put an OD pedal in front of the interface, all that hum goes away. I mean, just dead silent even if I crank the amp sim gain. It's great, much better than before when I was using an overdrive plugin.

I'm using the Hardwire CM-2 and there's no internal noise gate as far as I know. Wonder what's going on, is the pedal acting as a ground lift or something?
It could be a number of things but most likely the ground on the guitar. Test the ground out on the guitar. I had similar issues yesterday to find out the ground connection on the guitar broke off. Worked fine going into the amp, but into a pedal was distorted as hell.

With guitars there is no such thing as a ground loop. If the guitar is not connected to earth ground through the amp it creates hum. Most likely if the ground was messed up on your guitar then the pedal would and could offer filtering and a solid earth connection through at leas one of two or more cables, dramatically reducing the hum, but not all.
This problem with noise on only high gain stuff, and then sorted miraculously by something put in the chain ... It may be the pickup cavity.

Is this problem persistent with other guitars too?

If so isolate the pickup cavity with thin copper sheets on a guitar you are prepared to tinker about with!
Thanks for the suggestions. I checked the ground wire, pickup cavity, etc. and everything looked in order. Tried a different guitar, same issue, and found it made noise even when the guitar volume knob was turned off.

So after narrowing things down, that's when I finally discovered the source: an 1/8" AUX cable from my PC speakers was laying next to the breakout cable of the interface. One end was plugged into the speaker, other end dangling, speaker was off. The AC adapter (switching psu) for the speakers was putting out EM noise -- all the way to the tip of the AUX cable, and that was feeding noise into the breakout cable by proximity.

I moved them apart and it's fine now. Mystery solved!