Ground Loop?

Luxman 507uX.

I don’t see any indication the amp is Class II Listed. Can some one point it out...

Funny thing is, I didn’t remember seeing that either. I own exactly that model. :) I’m not breaking my back to find out. :-) AFAIK, double insulated gear has a dual square logo and I haven’t seen that. I’d have questioned if it was even legitimate based on how the unit is constructed.

Forgot to post the blog with the images I referenced, my bad:

https://inatinear.blogspot.com/2023/04/luxman-507ux-empower-project.html

There is a separate blog about how it seems the Luxman has the wrong leg fused here:

https://inatinear.blogspot.com/2023/04/luxman-507ux-ac-inlet-mistake.html

I kind of fixed it, no help from Parasound, but if I take a small piece of wire with a spade lug and slide it under the pot and connect it to the ground it goes away. I've never heard of such a thing it's not a hum but a chattering noise with static. Parasound has had it twice with no problems found. I've never spent so much money on something that's under warranty and the total lack of help is ridicules. Buyers beware.

Grounding Boxes

This may sound really dumb, and I don't have even a smidgen of the electrical chops that the old hands on the forum have; but I was having a similar problem awhile back with some new equipment and decided to make my own DIY "ground boxes" that use the RCA connections as a "signal ground." I found that in my system signal grounding only the CD transport and the DAC plus the REL subwoofers worked best and that every component need its own dedicated box. My boxes contained mostly sand and powdered graphite - the kind that hardware stores sell for lubricating door locks and such. Nestled in this mixture was a copper mesh conductor linked through the box to conductive wire leads soldered to RCA male connectors which interface with the female RCA connectors on the back of the components.

The upshot was that any little hums vanished and that the music became more relaxed sounding.