I have installed in my Audi (TT Bj.98) with Bose system, a new radio, which I have an adapter needed. He does not fit into my system (probably for older models) and is priced much too expensive for a passive adapter. Most need additionally a phantom power supply for the radio antenna and a noise filter for the RCA plugs. However, this is the Bose system or the Audi Electronics owed and no fault of this adapter. Return was not a problem and I quickly get my money back.
Not exactly cheap, but very good solution to replace the radio on an accessory radio. Please advance to check if your really a "quadlock" active system have. Because of the price conditional purchase recommendation for Audi owners with Bose sound system.