I recently installed 2 subwoofers in my truck and whenever I change audio inputs, FM stations, or turn the volume up from zero they make a thump (basically whenever the speakers start to receive a signal). I believe this is a problem with my HU because in my last vehicle (2000 expedition) i had the same problem with a different amp and subs, however i kept the head unit for my new truck. I was able to overcome this problem before by turning the LPF down on the amp and the thump would stop, but this time it persists. I've read it might be a grounding issue. Is there any way to fix the problem without getting a new deck? BTW i have a premier DEH-750MP deck, kenwood KAC-9105D amp, and premier 10" shallow subs.

 

found out that it was from RCA cables not being properly grounded in the head unit. solution was either a $20 part from the local stereo store, or run a wire and ground them myself. not having a spare $20, i ran a wire from the RCA to a ground.