One of my 5-channel JBL systems that is located in my garage is powered by 3 large Crown power amps and these are driven by an Adcom 5-channel home analog pre-amp with RCA input/output jacks. The Crown amps (XLS 802s) have 3-prong input (balanced??) terminals.
None of the amps are running in bridged mode.
I was doing some work with hook up, speaker changes yesterday and one Crown amp now has a significant hum but the other two amps do not.
How would you chase down the hum and in which sequence?
1. Switch input wires from amp-to-amp?
2. Switch the speaker outputs from amp-to-amp?
3. ground all amps to a cold water pipe?
4. disconnect all ground wires?