I have a 1998 A4 Avant Quattro with Concert Premium Sound. I tried to install a Matsushita (panasonic) cd changer that I was told would fit the round 13 pin connector. Radio was on when I plugged it in and a "whooof" emitted from the speakers. Now radio lights up, but no sound and displays nothing but color screen. Any advice would be GREATLY appreciated!!

 

check the fuses.
put the original cd changer back on.

if this doesnt work, IDK, sorry man.

 

Even if the fuse is still good remove it and put it back in. This can reset the radio.