Reinstall today in my new Audi, so I know the head unit is fine.

When I set the Power Antenna setting to Antenna, I get a hum in the rear, but the speakers and sub actually work. If I turn it off, and play the iPod, I only get front speakers, but no hum.

Bazooka powered sub is tapped into the rear speakers - grounded pretty well.

Also added in the Bluetooth adapter if that matters.

Any ideas on where to start? Does it sound like a ground problem, or a voltage wire in the wrong place problem?

Thanks!

the hum gets worse when I turn on the headlights - if that helps.

And the headlights trigger the illumination....

Sounds like you are feeding the factory amp high level speaker wires. Needs to be low level, or pre-amp.

Figured it out -

The rear speaker negative wires had not been connected. I connected them and VOILA the buzz goes away completely.

Sweet