I’d never had a problem with Ground Loop until my wife turned on an infrared space heater in the basement. I had no idea what was happening and it drove me nuts until I figured it out. What’s funny is we switched to a regular space heater and haven’t had any issues since.
Ground Loop?
I seem to have a ground issue with my phono preamp a Parasound JC3 Jr that just started about 3 months ago. I've tried very thing. A different Preamp (Moon 350p) replaced an Emotiva XMC-1 Different TT but still has the issue whether it's connected or not. I have 2 dedicated 20 Amp lines direct to fuse box and plugged them directly into the sockets bypassing my conditioner Audiance V8. It's a tapping sound with static but when I touch the loading pot in back it stops chattering but has a low-level hum. I have even sent it directly to Parasound and no issues were found. Going nuts!