Jameswei's suggestion is a good one. I have had hums and buzzes, and never, never had one that could be fixed by using a cheater plug.
First, what did you change? Are you saying that all of a sudden there's a hum and you've plugged nothing else in to the system? If nothing in your hifi system, what other electrical appliance have you plugged in to the same or an adjoining circuit? Buzzing hums are most often caused by dimmer switches for the lights, refrigerators, or sometimes odd components.
I fixed the refrigerator problem by using a different circuit. I fixed the dimmer switch problem by using a thick "triple shielded" interconnect between the preamp and amp (or you could leave the lights off). The old tuner that caused the same kind of buzzing hum, I removed.
So, look for anything new non-hifi that was plugged in anywhere near and unplug it. See if that helps. Turn off the lights. If you still have the problem, try shielded interconnects.