Well, fixing the Blitzsafe didn't fix the problem, although it needed to be fixed. I'm sure that having an audio ground hanging by a thread is not a good thing. It was a PITA to get the socket out of the housing in order to resolder it. And then when I was done soldering the socket, I discovered that was not enough slack on the audio signal wires for me to be able to place the ground socket back in the housing, so I had to unsolder it, place the socket halfway in the housing, heatsink it somehow to prevent melting the socket and re-solder it. Way too much fun for my liking.

Anyway, as I said, that didn't fix it. I eventually traced it to being a bad ground connection at the sled connector. I couldn't see anything wrong with the crimp, but for some reason wiggling the wire made a difference. I also discovered that both microphone crimps were bad, and the amp remote line was virtually out of the connector. (I'm sure that didn't help with the GPS noise!)

So I ran a 10ga ground line to the back of the sled using the 4mm threaded hole, and then tapped the existing looms ground into it. That seems to have fixed the alternator whine and empeg noise completely. What (very little) noise remains doesn't appear to be empeg-related - I can also hear it if I play a blank tape. I'm guessing that it's just noise picked up on the 12V line in the loom. When I ran the ground line, I included a beefy 2 position molex connector, so I could easily add a 12V line too. I'm now trying to decide whether to take it from the distribution block behind the driver-side dash, or go the hassle of running it through the firewall straight to the battery. Hmm. Decisions.