On my 19992.8 A6 avant quattro, the radio (Audi / Bose Concert) has been making a crackling noise as music is played. Then when I turn it off, I still hear the crackling noise. It even happens when you turn it off and remove the key????

Any suggestions on resolution to this problem

r u sure its coming from the radio? because if its still making the noise after the car is off then i'm not quite sure thats the radio thats the problem.. can u explain a little more? where is the sound coming from exactly?