In reply to:

Wouldn't a ground-loop problem cause a hum?

Hiss, hum, some of the speakers, all of the speakers....whatever. I don't know and frankly wouldn't care as long as it fixed the problem. The point is that it couldn't hurt to try. If it works it would be a cheap fix and if it doesn't work he is only out the 59 cents it cost to try.

I live the life I love and I love the life I live.