Audio Systems: whining noise, channel amp, head scratchers

Question
Hi,Im stumped. I have installed many systems and track this down. ok the system consist of cd deck,electronic 3 channel crossover,4 channel amp and a 2 channel amp. I am getting a whinning noise that only slightly increases when accelerating. I have seperated the power wires from the rca (all wires are top notch stuff). I disconnected receiver rca"s from crossover and still noise. Disconnected just one plug from crossover noise goes away,which one speaker is not connected now.mSo plugged it back in and noise, disconnected same plug from amp,no noise. Tried this with the other plug same thing and this noise is only being created from the 4 channel amp. I have tried regrounding and no help. would a ground loop or a inline filter work? I also found out that it has an aftermarket perfomance ignition system (msd 6a box) Any suggestions  

Answer
Rob,

  i would chalk it to just one of those "head scratchers" i would stop by radio shack pick up a distortion block/noise eliminator wire it in and that should cure the problem .. the performance ignition could be a factor but from what it sounds to be in the 4 channel amp somehow maybe loose hardware inside bad shielding ect.. but the easy wire ins should fix it up

thanks