I've been having a noise problem on my board. I have identified a few possible culprits. One of them seems to be an interesting case. It's a digital pitchshifting pedal for guitar (this is a combo bass/guitar board). I put it only in a chain w/ a true bypass dirt pedal and found the following results: Pitchshifting on---no noise Pitchshifting off---no noise unless the dirt is on, then I hear hum This is definitely hum and not the obvious hiss from the dirt pedal. The pitchshifter is allegedly true bypass. Does this make sense? Any chance a good isolated power supply will help?