Originally Posted By: Ryszard
Okay, I have several new data:

1. There was no fluorescent light in my room. The closest CFL is two rooms away.
2. There are no dimmers or "choppers" in the house.
3. My DAW froze briefly yesterday. During that time the static noise disappeared. Does this point to the VPU? (I hope not, I paid $200 for that sucker.)
4. And the biggie: I put in a 3/2-prong adapter, and Lo! both the hum and static have become barely audible. As in, I have to put my ear up to the drivers to hear it. The noise coming from the liquid-cooled PC is louder. The hum and static are barely audible from my normal listening position.

Onward.

1. & 2. - good.

3. - Probably not the CPU directly, but there may be poor onboard PSU filtering. (there are CPU power supply regulators on motherboards these days - have been for a long time) It's also possible the 5V filtering for the USB supply is not great.

4. - Excellent - now we know there is a definite correlation with an earth loop somewhere. Is there anywhere in the signal chain where an earth can be lifted that will always be part of the overall signal chain?

Perhaps you can describe where connections go from PC to speakers?

Also, given that the hum is only reduced and not completely eliminated there is still some tracing to do. That said, removing a signal earth somewhere rather than the PC's mains earth MAY do it.

--=-- My credo: If it's worth doing, it's worth overdoing - just ask my missus, she'll tell ya laugh --=--
You're only paranoid if you're wrong!