I had a problem with my Empeg where I was getting hard drive noise and alternator whine in the following situation:

- Empeg's continuous power wire was hooked up to the constant +12v power from the battery (normal connection).
- Empeg's ignition wire was hooked up to the car's ignition wire (normal connection).
- Amplifiers were connected to constant +12v from the battery (normal connection)
- 12v USB phone charger dock with line out and Bluetooth adapter with line out were connected to the empeg's aux-ins and got their power from the car's IGNITION WIRE. <-(THIS WAS THE PROBLEM)
- Everyone connected to common ground.

Until I moved the USB phone charger and the Bluetooth adapter to the +12V constant power (instead of from the ignition wire), I got the ground loop noise as long as they had any kind of power applied and/or they were attached to the empeg's RCA aux-ins. If I removed them so they didn't have any audio cable connection and/or didn't have any power, then I got no noise. When I moved them off the ignition power and onto the +12V constant power, all the noise went away and I could use them normally. Of course, I don't want them vampiring power off the car battery when I'm not using them, so I use a separate switch to turn them on and off (considering replacing that with a relay so I don't have to remember the switch).

Correct me if I'm wrong, but don't most cars power their cig adapters from the ignition wire? I wonder if you try the same thing, but get all your power from the +12v constant instead of from the cig lighter socket, if the problems will go away for you?