Grounding problem in the amp.

[legarem]

I placed 16 ohms resistors between RCA and the wire that goes directly to the chassis and it cured the problem. My spakers are 91 db/1w/1m and there's not a hint of hum or hiss with my ears near the speakers.

 

[Bonsai]

Ok. That’s not the same as putting them into the signal return since that is now mainly flowing into the amplifier module.

 

[phase]

A dual mono amplifier is great until you plug it into a preamp that has ground shared between L/R channels. Still better than sharing a power supply though.
Someday it would be nice to have a true dual mono back to the source.

Glad you found a solution.