Following some system enhancements that included the addition of a remote gain control for my subwoofers (the gain pot is located on the front face of my center armrest where my fingertips just rest on it -- very nice!) I have some pretty awful noise in my subwoofers. This is the first time I have ever had noise in any of the three stereo cars I have built, so it is somewhat distressing.

For anybody silly enough to be interested, I have attached a zipped bitmap file of my signal path diagram that might shed some light on the problem. In a nutshell, I am getting a constant warbly ~50 Hz hum from my subwoofers, even when everything in the car except the subwoofer amp is turned off: engine, radar detector, empeg, CD player, equalizers, a/d/s 8-channel amp, I mean everything except the sub amp (oh, and the dashboard clock) is turned off or disconnected. As long as that amp has power, the subwoofers hum audibly enough that I can hear it in quiet music passages.

If I disconnect the RCA inputs from the amp, the noise goes away. The noise gains/loses volume proportionally to the gain setting on the amp. A test with a different but similar amplifier caused no change in behavior.

The fact that there is nearly 25 feet of RCA cable between the head unit(s) and the subwoofer amplifier, running through a Sony switch, a pair of EQT equalizers, a pair of "Y" connections and a remote gain pot before it ever gets to the amplifier tells me I am asking for trouble, and I got it.

I am leaning towards an open connection in the shielding of one of the RCA cables causing loss of ground as the root cause of my problem. Does this sound reasonable? Or am I overlooking something obvious?

tanstaafl.