Yes, that was the first thing I tried. Grounding the aux shield with the XM plugged in definitely made the noise worse. I know the aux input is supposed to be floating, but I think the ground loop isolator made an improvement. In any case, it is still not satisfactory.

I think my primary noise problem is not a ground loop: I have unacceptable noise even if I unplug the cable from the XM unit and ground the aux shield and two signal lines to the empeg ground.

It just seems wrong that I'm running analog FM into a digital input and digital XM into an analog input.

I'm considering adding the Eclipse unit w/ digital aux-in and running both empeg and XM digital into a S/PDIF autoswitcher. This would give me an all-digital solution (of course for more $$$).

-Jon