Thank-you for the frequent code updates!

For the noise, my theory is that perhaps the hard drive motor(s) of the empeg are back feeding some noise. Feel free to blow away this theory by stating you are using SSDs (or CFs) instead of mechanical drives!

Somebody really clever (like Patrick or some others on the BBS) could probably point out a simple array of capacitor values to use to filter out such unwanted noise. Eg. my untrained mind might attempt just stuffing all of these in parallel across the 12V/GND lines in front of the BT power supply: 1000uF 100uF 10uF 1uF 0.1uF 0.01uF. But then I have bins on hand here with all of those.

I wonder if it might help to instead draw 12V source power for the BT board from the 12V on the tuner connector?