Hum issue - driving me more crazy

But there is constant low level hum - right side only EVEN with preamp and XOVER turned off.

I agree with Gs5556. Try some ground cheaters.

Just because you turned off the preamp and xover that would not break the ground loop current path through the right channel amp.

Have you tried to isolate the right channel amp from all other equipment? Nothing connected to the input of the amp... That would tell you if the low level hum is caused by the amp or not.

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I have used cheaters in all possible combinations with resolution of most of the hum BUT not the residual in the right channel only.

I have disconnected the dimmers from the circuits in room->no help
Reversing amps and XOVER outputs -> no help
Ground lift change on amps->no help
Preamap powered off and XOVER powered off -> no help
Electrician has reevaluated wiring and says all is OK
Separate 20 amp circuit has its own ground
No lights are plugged into stereo circuit

Unplug interconnect at right amp -> RESOLVES HUM
" " " RIGHT XOVER OUT -> RESOLVES HUM

Bringing the IC to the right amp TO ABOVE the floor-> RESOLVES NOISE. In my unknowing frog brain, this implies something is inducing noise in the right sided IC (when under the floor - down about 12-16" is all though). But nothing can be identified so far

As I know not enough about electronics:
Unplugging or turning off preamp or XOVER does not help - > are these eliminated as issues causing ground loops etc when OFF? Or are they still part of a system with potential "current flowing" (even though "off")

Does disconnecting IC from AMP (or at XOVER) TELL SOMEONE WASSUP?

Perhaps, as a (sort of) simple solution - > Would balanced from XOVER to AMP resolve the issue regardless of cause?

Thanks

Bringing the cable above the floor may be moving them away from fluorescent ballasts. Speaking of lights, do you have any low voltage LED or decorative lighting that feeds off a DC transformer? These introduce DC into the wiring that get into ground loops.

To answer your question: yes, balanced IC's are the best way to go because the shields are tied to the chassis instead of signal ground. But somewhere, there is something that is amplifying your problem -- computers, improper CATV or Telco grounding, etc.