Originally Posted by djue
Grounding the RCAs between the Wet Sounds EQ and amps almost completely silences the hum. Note that grounding the RCA between the source unit and wet sounds EQ does nothing. And of course disconnecting the clarion remote from the Big computer completely resolves the noise with RCAs grounded or not. For those that are interested, the noise is originating from the Ilmor 5.7 throttle position sensor. The same piezo type hum can be heard direct from the sensor area. The sensor evidently calibrates for 2 -3 seconds when the ignition is moved to start. Then shuts down until the engine is started. You can hear the noise through the stereo in those 3 seconds then it goes away until engine start. When I disconnect the TPS wires, the noise is gone.
It's weird that a TPS would cause any noise. Assuming the Ilmor is very similar to a GM/Indmar engine, the 2-3 second time window seems like it would be from the IAC or fuel pump relay (the pump primes for 3 seconds on a GM or Indmar engine). A TPS is just a potentiometer and isn't actually controlled by the ECM, it just receives a control voltage and returns what it will, based on its position, to tell the ECM what to do.
Good to see that you got rid of most of the noise.