I have a 2008 Mini R56. In installing an XM radio device, the person who put it in accidentally hit a wire when installing a ground. The wire was repaired and all was fine. Some time later I got no audio..nothing, no Tuner, Aux or anything. I brought the mini to an automotive audio expert and he said there was no power to the amp. But he was unable to go further. I brought the car to a Mini dealer who said I need a new amp. I didn't have the $$ to spend on the repair for the dealer...so I purchased a used amp on EBay, installed that and it still had no audio. I removed the amp and returned it. I then sent my amp & head unit to UNITED RADIO in Syracuse. They tested both units and they work fine. They told me there is a problem with the "optical loop", maybe something within that loop failed and that's why there is no power to the amp. Does anyone know how I can diagnose this and get my radio back working??