What would cause noise (ground noise?) when touching the volume control and tone controls?


I have a new preamp that I recently hooked up and I'm getting some interference or what may be ground noise but I only hear it when I'm physically touching the metal volume knob and tone controls.  When I touch the metal top of the case in addition to the knobs, the noise will subside.  Just looking for ideas to help isolate the cause.  I think the case itself just isn't grounded sufficiently.

I have tried new power cables, RCA cables and plugging into different outlets with no change.

tubeguy76

@cleeds Ah... it's a "new to me" preamp, but it's a used unit.  Fairly new though.

@antigrunge2 I don't have a phono setup, just a streamer connected to a DAC and the DAC connected to the preamp. 

I can reach out to the preamp maker, just wanted to see if I could solve it myself before doing so.  :)

I can reach out to the preamp maker, just wanted to see if I could solve it myself before doing so.  :)

@tubeguy76 This sounds like the controls are not properly grounded and the case may not be either. I would talk to the manufacturer first, since opening it up to solve it yourself will likely void the warranty.

@atmasphere Yeah that's what it appears to be.  I'll reach out to him and maybe he can help me solve it without sending it back for some TLC.  

Have you tried plugging all your equipment into 1 power outlet strip?

Could be a ground loop.

Joe Nies

Back in the day, I had the same issue with an amp.  It had a two prong A/C plug, and turning the plug over, i.e., reversing the  prongs, solved the problem.

I guess since only one prong was supposed to be driven and the other was supposed to be a ground source, they must have wired the ground source to the chassis ground.  So if that prong was plugged into the driven side of the socket, the chassis wouldn't be properly grounded.  Turning the A/C plug over was the fix.

Your new unit probably came with a three prong plug that can't be turned over.  Maybe the internal wiring of the A/C connection needs to be switched.