My sisters 04 C230 has just gotten a problem. The cars radio comes on but no sound at all out of the speakers, tried the cd changer and still nothing. I told her it was probably the amplifier but I am not certian. Is this a good guess to what here problem may be. I checked all the fuses and they were all fine. I didn't see a fuse for speakers but I did see fuses for radio, cd changer, and satelitte radio and they checked fine. If it is the amp where is it on this car?