I have my proceed pav/pdsd hooked to Harman Kardon signature 2.1 amp driving the speakers. The L,R, and Center are working fine. When I try increasing the sound level of rear speakers the amp goes into protection mode. There is no sound coming from rears at low levels. The same thing happens while the rear speakers are disconnected, so there is nothing wrong with the speakers. When connected and I check the sound levels on the speakers I hear a popping noise when I go to the rear speakers but no sound. The wires going to the rear speakers are new and fine. Same problem persists when I hook a different amplifier and different sets of speakers in the rears. Where else the short can be in the preamp???? BTW teh wires connecting the preamp and the amp are fine. Harman wants $1300 to look at the preamp.