Ugh. Fiddling around in the dark. And not the kind that is most enjoyable either.

Hmm. Turns out I potentially have 2 problems. Firstly, noise appears to come from my GPS box. ie, It disappears when I unplug it from the serial cable. For the record, this is powered from the remote amp line, and serial ground. The case is metal and (was) grounded to the serial ground. Removing the case ground didn't change anything. The noise from this appears to a variable length burst approximately 1/second. I'm guessing that this is related somehow to the 1/s message output from the receiver, so what I am actually hearing is the serial transmission.
So what could be causing this to appear on my empegs audio outputs? It doesn't appear to be related to the second problem, correcting the second problem doesn't affect this, and that is worrying.

My only thoughts on that subject is that my GPS transmits RS232 at 5V/0V levels and not 12V/-12V. It doesn't affect functionality - GPS works fine. But maybe the empegs serial port doesn't like 5V signalling. Even so, it still shouldn't appear on the outputs.


Second problem; EMI being picked up on the outputs. Grounding the barrels of the RCA adapter reduces it. Any barrel, F/R, L/R, helps. I'm guessing that if I gave all 4 a good grounding this noise would be eliminated.

Now I'm wondering if perhaps my 4V line outs are somehow shot. I seem to remember someone else recently having a ground issue with their sled outputs. Anyone remember where that thread was?