Originally Posted By: JohnK
Rob, the fact that this noise is present even when the coaxial cable to the sub isn't connected and the only connection is the power cord, shows that this isn't a ground loop noise, since there's no connection to form a loop. Apparently there's a problem in the power supply section of the sub amp and either the rectifier or a filter capacitor is going bad.

Yeah, I never thought it was a ground loop but I went through the checks just to eliminate. Just another item to vie for my attention.

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