help with hum

One of my systems once suddenly developed a hum. I found that one of my wall mounted light switches was somehow the source. Flicking the switch on and off would stop the hum. Unfortunately, it would recur from time to time, but not so annoyingly as to motivate me to replace the switch rather than get up and flick it again. Good luck.

Not a big deal...easily fixed. All you need to do is "break the ground" on one of your grounded components in your system(amp,preamp,cd,waterver). This should do the trick. Just use the "cheater plugs"(3 prong down to 2) you get at any hardware store is what you put on the end of one of your componets power cables. The system is still grounded through connections between them.
If that doesnt' solve it, it's probably your interconnects or speaker wires being interfeared with each other, or the powercords. In that case(if scenario #1 doesn't solve the problem), just move you're interconnects or cables around until you identify the hum..or eliminate it!
Good luck

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.