I’m glad you checked and fixed it.. Micro Arcing. The valve unit has all kind of little antenna inside the case picking up the micro arcing in the ground circuit.
Pretty easy to see how it could get noisy. I imaging it didn’t help with floor noise either. I suspect the ground on the SS was lifted and or a different grounding setup than the Valve unit..
I been tinkering with a secondary parallel RJ45 central grounding system. I thought what the heck, how easy could it be, a lot less expensive setup than someone else’s 2-20k system and RJ45 patch cable is very inexpensive and QUIET.. Easy to make up. I gutted a brand new older 100mb hub for the main ground collection point.. Super tight fitting RJ45 females terminals and a heavy gage sheet metal case
A work in progress but sure is working out.. I have 35-40 dollars in it..
Now an EARTH box ground? LOL I’m not buying into that one just yet..
BUT you never know.. Have to consult with Master M and get a little lateral advise :-) He's always tinkering..
Regards..