Just an idea, I had a hum problem with my center channel and mono amp for driving it. I inserted a Jensen Iso-Max isolation transformer in the interconnect, and 90% of the noise went away. It might be something to try. I have a two-channel analog set up (using the same main speakers, separate tube preamp and SET 300B amp) with no noise issues.
Hope you get it sorted out.
Regards,
Dan