Need issues fixed with Audi TT Bose system - who to go to?

The normal cause of engine noise in the stereo system is the ground. In any 12 volt system there is a 12volt + and a 12volt -. Often times a vehicle manufacturer will ground all of the dash instruments to one central location. This is great for them but bad for car stereo enthusiasts. When we hook up our new stereo we often times (if done properly) will use an installation wire harness. This wire harness will match up to the vehicles wiring exactly. So your ground and power are coming from the fuse block and a central ground location (vehicle standard).

A simple solution can usually fix this engine noise problem. Change the stereos ground location. Most times this can be done and un-done(if it doesn’t help) very easily. Behind the stereo will be anywhere from 10 to maybe 16 wires coming out of the stereo into a wire harness clip. Between the stereo and the first wire harness clip you will need to cut the ground (Black 12V-) wire.

This will break the ground and the stereo will not turn on at this point. The part of the wire that is coming from the back of the stereo will need to be lengthened and run to an alternate grounding location. Most of the time there is a bare metal dash frame under the upholstery that you will see when the stereo is removed from the dash.
With a digital multi-meter in hand you may test for a good ground source. Make sure to set the meter to test for continuity. You can make sure that the meter is set correctly by touching the lead ends together, this should give a beep or chirp from the meter letting you know that there is continuity. Clip one of the meter leads to a known good ground (somewhere in the door jam usually works) and then you may begin looking inside the dash cavity for a ground location.

Once you have a beep or chirp from the meter you know you have found a ground location. We’ll only know that this is a good location or not once the ground is hooked up and we turn the stereo on. Until then, cross your fingers and hope for the best. Hooking up the stereos ground wire to the new ground location is up to you. Every situation is different so you may need a crimp end or some other modifications inside the dash cavity to get the ground wire hooked up.

Just changing the stereos ground location will often resolve the engine noise problem. When this doesn’t work we resort to a “Ground Loop Isolator” or “Inline Noise Suppressor”. There are a few different styles that are used for different applications.
There are noise suppressors that are used in the power line, in the RCA/audio cable lines and some with 3.5mm stereo cable input and out put. You must determine which is right for your application.

Some stereos will only create this whining when there is an auxiliary audio input used. These will usually be something like an MP3 player. There are ground loop isolators for use with MP3 players