My Harman Kardon AVR 220 reciever's front-right channel isn't working. I have switched the two front speakers and the right speaker works on the left channel so it is not a problem with the speakers or wires. When I turn the volume up loud enough, (-10dB or more) the speaker emits a crackling sound (not a constant crackling, more like a distorted (very distorted) version of what it should be playing.) I have done a microprocessor reset and the problem still persists. I have taken the cover off and nothing looks burned/disconnected, etc. but I'm not sure what to look for. Any suggestions? Thanks!