thanks for the info, the amp is clean and looks almost new, so I know for sure its not the amp. If it was the amp the gong sound wouldn't work either, so I don't think its the amp, however I did some digging around and I found a bmw service bulletin related to the exact same problem I am having. The problem seems to be related to a strange buzz from the speakers I also occasionally have with the audio off. I think I am thinking it is the second of the two problems listed in SI B65 13 10, look at this thread
https://www.e90post.com/forums/showt...=105325&page=3