Ground Cheater plug or....

Try the cheater plug and see if that does away with hum,if it does take it off and unplug each component one at a time and see if you lose the hum. This way you can verify what is causing the hum. If it is your amp and it not audible when playing music I would not worry about it.

Someone clearly needs to produce an "audiophile" cheater plug for 50 bucks or so :-)

Here's another option & one I use myself on my CDP. Buy a Volex cord which is very good for around $7 from Newark & cut the grounding pin off w/some stout wire cutters. I do prefer to have my amp grounded. PS Audio & TG Audio sell ungrounded cords I believe.

On some PS Audio power cords you can remove the grounding pin.

Grimace, you can get hum in many ways.

Sometimes it is because the system components are plugged into different breakers.
My JL Audio subs will hum because they are plugged into a different dedicated circuit and they are on the opposite side of the breaker box than the rest of the system. But once the rest of the system is wired up and powered on the hum goes away completely.

But many times it is caused by cable TV connections.
Be it interconnects, power cables etc. You can buy isolation adapters that connect to the cable coax that will eliminate that hum.

With all that being said, and if all else fails, hum can drive me absolutely crazy. If it could be determined which component is causing the hum, then I would disconnect the ground in the outlet that component is plugged into.