I have an external stereo amp that is being driven by a 7.1 receiver with pre amp outputs.
When both units are powered up, no audible hum or hiss is present. However, when the receiver is powered off and the external amp is powered on, a loud audible hum is present.
Both amps are drawing power from a "protected" 120V power strip.
Is this a result of improper grounding? Should I run a ground wire from the chassis of the external amp to the chassis of the receiver?
Thx