Ground Cheater plug or....

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.

I've been through all the components. The hum remains even if the ICs are disconnected from the amp. There are a lot of items in that room though: lamps, TV, ROKU box, DVD players, two seperate power supplies. The only thing I haven't tried is taking the amp to a different room/circuit breaker, mostly because I'm too lazy to haul the entire system along to test it.

RDav... you shouldn't assume that because someone is using aftermarket cables that they foolishly dropped a mortgage payment on them. There's nothing "uber" about my PCs, but at about $100 bucks they were an audible improvement over stock cords. Sorry if your hearing isn't that good. Maybe you should take up knitting.

Absolutely do not use cheater plugs. They defeat the ground that is there to protect you, your equipment, kids, wife, girl friend in the event of an electrical fault. Find and fix the electrical problem causing the need for a ground loop. Be it, bad interconnect cables, bad electronics, bad ground system in your home, however, you will find many people telling you to use cheaters. You are asking for trouble if you do this. No electrician in their right mind would tell you to defeat the home ground system by using cheater. It is relatively easy to find the cause of the problem, isolate it and fix or replace it.

if you have a hum or ground loop, I can tell you how to systematically find it, isolate it and what you can do to get rid of it. But do not use cheaters.

enjoy

The hum remains even if the ICs are disconnected from the amp.

Then the hum is most likely not being caused by a ground loop, and it most likely would not be fixed by either a cheater plug or by disconnecting the safety ground inside the outlet.

The reason I say "most likely" is that there is a SLIGHT possibility that the hum is being induced by two different means in the two situations. By a ground loop when the preamp is connected, and by pickup of emi (electromagnetic interference) when it is not. With nothing connected to the amp inputs the possibility of emi pickup is increased, because without the preamp being connected the impedance at the amp inputs corresponds to the high input impedance of the amp, rather than the much lower output impedance of the preamp.

My suspicion is that the amp itself is generating the hum. To confirm that, put shorting plugs on its inputs, and turn off or unplug everything else that is nearby, that could conceivably be a source of emi. If you don't have shorting plugs, and assuming the interconnects are unbalanced, connect them to the amp, leave their other ends unconnected, and WHILE THE AMP IS TURNED OFF stuff some aluminum foil into the unconnected ends to short the RCA center pin and ground sleeve together. Make sure that the foil is securely in place, so that it won't dislodge when you turn the amp on. Do not let anything or anyone touch the RCA plugs while the amp is on. And after assessing the hum level do not remove the foil until a minute or more after you have turned the amp off.

Also, this paper may be of interest.

Finally, as I see it creating a code violation inside of an electrical outlet, where it might be forgotten about in the future, severely compounds the already non-negligible risk that using a cheater would represent.

Regards,
-- Al