No Sound in One Channel
 

Hello, newbie here. Here's my setup: HU - Pioneer DEH-4400HD 4 channels pre-outs (2 sets of RCA), Amp- Kenwood Excelon X801-5 (3 sets of RCA:A, B, Sub). Mid Speakers- Polk Audio DB-401, Polk Audio DB-521, Subwoofer- Polk Audio DB-842DVC... One channel from HU is connected to A channel in the Amp, 2nd channel to B. Kenwood Sub output signal is created by amp. I followed the connections as specified, but no sound is coming from 1 set of speakers (front). Now when I switch the connections of the RCA cables, the sound output is reversed. The subwoofer is working. I can "feel" vibrations from the silent speakers, but no sound/music. What did I missed? Does it have something to do the input sensitivity? Thank you in advance.