Tony, very thorough response - thanks. You will be happy to know that, thanks to your suggestions, the problem is solved!

Originally when I was troubleshooting this, I did go into a little more detail than I mentioned in my post. I tried pausing the empeg during playback, and the noise was still there. I also tried hooking up the empeg's RCA outputs directly to the Sunfire power amp, and the noise was even worse.

In your post, you mentioned it was still possible to have grounding problems with home use. This clued me in that it might be a power supply issue, where the power supply might not be locking down the ground tightly enough. I have two empeg power supplies - the tiny one-piece one that came with the unit, and the $30 extra power supply which is a big brick with a separate standard IEC power cord. I originally used this bigger unit, thinking that this big $30 brick power supply will be cleaner than the tiny thing included with the empeg.

Well, based on your post, I switched back to the tiny wall wart unit, and the problem is SOLVED! Playback was absolutely clean. I am totally thrilled!

Who should I contact about exchanging this power supply for one of the small one-piece wall-wart kinds? There was the car stereo email address posted elsewhere, is that the right one? It sucks to pay $30 (plus shipping!) for such a tiny thing, but I'd just be happy to have a power supply that's clean for the main stereo.

Thanks again for your time. Now a very happy customer (well almost... did I mention I still need a red display to match my car? Arrrgh!),

- Chris