Noise, but only when using multiple RCAs

Sorry, it must have been someone else who also had this problem.

The size of power cables will have nothing to do with this kind of problem.

How did you set your input levels (gain)?  How did you determine that "25%" was the correct setting for your setup?  Too high a gain setting will introduce all sorts of problems, including noise.

Well, the 25% was the level at which the noise is unnoticeab le - not the correct gain level needed for my setup.  I found it was best (using the 75% deck volume refrence level method) at around 50-55% - unfortunatly then I have a considerable amount of noise at low volumes.   I'm going to try running a deck external to the vehicle and test  with the car running and see if there's noise, that will elimate the amp as the source of the problem is the noise isn't there I would think.   

James