I'm curious...I had a lot of noise using the adapter to send the pre-out signal to my aftermarket amp. I grounded my RCA shield like this post says and I got rid of a lot of noise

http://forums.audiworld.com/audio/msgs/13471.phtml

But my question is, doesn't the Blaupunkt adapter do this for you, wire the grounds from the RCAs together and sending into the "Commmon-ground" pin?

I's also advisable to run an additional ground to the chassis of the HU from a good earth point behind the dash.
You'll notice that Audi in their infinite wisdom chose to ignore the industry standard of using a shrouded/earthed connector for the pre-outs, so the low level signal is completely exposed where it connects to the HU.

Just read that because CC who installed my amps I saw them plugging and unplugging rca's while the HU was on and so i'm pretty sure the ground plane in my HU is broken