Thanks for the inputs

Tonight's experiment was to run a piece of #12 stranded (soldered to the terminations) from the PEM nut on the back of the Empeg sled to the Faston tab on the Becker shell. This provided the best result yet for Empeg noise, but I can still hear it.

I am convinced that the Empeg digital circuitry ground currents are present in the audio output shields as evidenced by the fact that it will operate without any other ground.

I agree with you about the Becker, the Aux in has a small pigtail shared for both channels, on a wimpy little connector pin.

Redoing the grounds so that the Empeg power is not routed through the Becker's wiring harness might help but I have, so far, tried to avoid tearing up the Porsche's harnesses. I already have virtually no interconnect, just a pair of double male RCAs between the two harnesses. Do you have any problem with alternator noise?

Lynn (2000 S)