You'd actually want not to do anything, since the audio source is a dozen feet from the amp stack, and the entire thing is wired with unlabeled undocumented CAT5. It's pretty impossible to tell what the hell is wired to what without bringing the whole company to a halt. They're a LARGE Toyota dealer nearby who just expanded one of the zones: it's the Toyota waiting area, about 3,000 square feet, with a Starbucks and a Subway. (The AAA and DMV offices are at the other end, in the Lexus part of the property.)

I'm figuring the buzz is coming from the cabling that goes out to at least three other racks on the property. There's a transformer isolating the XM radio from the audio system, but then these different buildings are all connected together. With freakin' CAT5. It's a mess we'll conquer.

EDIT: there's more going on here. See [Link: remotecentral.com].