Krell KAS amplifier hum

Thank you all for taking the time.  After my first failed attempt last night, I decided to plug all "in" and listen to music instead :-)

Tonight, I will try what has been recommended.  Something else I forgot to mention; I have a cable line and box in this room.  The cable line runs parallel to the XLR (they do not touch) and is also plugged into the same 15A outlet the power distributor is plugged into...

with kind regards,
Jose

@ jg2077,

Does the cable box connect to the audio system, in question, in any way by wire type ICs?

Does the cable box 120V power cord have a 3 wire grounding type plug? If yes just for the heck of it unplug it from the wall convenience outlet tonight before you start disconnecting things for testing. Even if there is not any ICs connecting the cable box to the audio system.

A question that should have been asked at the start of this thread. Have you always had the hum in this audio system? If not at what point did you first notice the hum?

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@jea48  - the cable line plug is a wall-wart and does not have a ground pin.  It is not tied (a part of) the sound system.  I'm not sure when i first heard it...you see, I'm alternating amplifiers (also use ML 33H) and did not pay it much attention.  I will certainly try what you are suggesting and report back.  Thank you for contributing.

Respectfully,
Jose

Update - the pre is plugged into a common 15A outlet; the amps are plugged into a dedicated 20A outlet and ALL else is unplugged.  I still hear the same amount of hum.

I installed a "cheater plug" between the pre and wall outlet,  I hear less hum than before, about 70% less.  I cannot hear hum from my listening position (10ft) away.

The "common" 15A leg has 7 outlets, 3 of which are being used.   1 outlet in particular has my humidor plugged into it. Unplugging everything from this 15A leg yields no change.

Thank you, 
Jose