I have somewhat of a similar issue, actually the complete opposite, I have feedback into all of my speakers(really bad ground whine and a buzz with the lights on)Tried grounding the RCA cables with no Luck. Had this happen once before on my old unit, got then circuit city to swap out unit for me, it went away, which makes me believe it's internal to the unit. Anyone know what it may be and if it can be fixed. I have a z1 in a 2006 trailblazer. Thanks