my 4 channel amp is a 800 watt sony xplod, the sub amp is a power acustic saphire series 1200watt 2 channel, I have a 2.4 farad digital cap. the pre amp out puts are all 4v. for power the main 12 volt line is run along the passengers side beside the seat under the door sill, the remote wire is run on the passenger side of the center hump, the rca's are all twisted pair and are run on the drivers side of the center hump, so I don't think its a matter or the power wires causing a cross induction. the 4 channel amp is set for high pass, and the 2 channel for, of coarse, low pass. even the speaker wire is a twisted pair wire. I went through a good expense when I installed this system to avaoid signal distortion. I just want to find the problem without spending money on unneccessary filters. when I turn up the music to normal volume ( 30 out of a possible 34) you can't hear the whine, of course I didn't hear my first motor blow either but at lower normal humane volume levels it's there. thanks for the help, keep it commin.