Hum problem

First of all I don't believe the Monster is up to level of your equipment and probably doing more harm than good. Reduced dynamics etc. Secondly; as Rwwear stated, try floating one of the grounds with a inexpensive ground lifter you can buy just about anywhere. Try doing that on each piece individually and see if that helps. Are any of your power cords running parallel to interconnects etc?

Check to see if your power cords are running along next to your interconnects. If you can move the power cords a foot away from the signal carrying wires, do it. If you must cross a power cord with a signal carrying wire, then cross at 90 degree angles. This may not cure your exact problem, but it could, and it is good general practice.

i had the same problem & i got a mondial magic box it goes on the catv line the problem was completely gone.

The Mondial Magic Box is a ground break for the cable TV.

Drop the ground. A couple of cheater adapters(3prong male to 2prong male)will do it. Most any supermarket or drug stores carry these devices.