Help with amp hum

[the flying grape!]

So I've been getting back into guitar playing, and I've noticed that my amp when plugged into an outlet in my music room hums noticeably. I can have a guitar plugged in with the guitar volume all the way down and the amp hums. I can have nothing plugged into the amp, and the amp hums.

When I took the amp to my den and plugged it in, 90% of the hum was gone. So it seems to me that the electrical circuit in my music room is the problem. However, I don't know what the problem is or how to fix it.

Any suggestions?

[Ed52]

Could be reversed wiring in the electrical outlet. Buy a 3 pronged polarity tester at your hardware, Home Depot or similar. It has lights that indicate what kind of connection problems could be in the outlet. It's a good idea to have one anyway...are you sure every electrical outlet in your home is wired correctly?

A missing ground connection or a reversed hot/neutral connection could cause the hum. Also lights or appliances in that room or on that circuit that the amp is plugged into could also be a source of interference.

[the flying grape!]

Yeah, I checked it with a tester, and the circuit appears to be wired correctly. Turning off the CFLs in the room only makes a minimal difference, so the electrical noise has another source. The room has some circuits that are switched by a light switch on the wall, so I need to check that circuit also.

[Ed52]

Check a dimmer switch.

[Mtl-Marc]

Turning off the CFLs in the room only makes a minimal difference, so the electrical noise has another source.

Turn off every CFL lights in the house.

[Ed52]

You can also try flipping the circuit breakers (fuses) off in sequence and isolate the noise source circuit and then check all items on that breaker circuit. Also plug a cheap AM radio into that outlet and listen for hum or noise.

[jtls8]

A power conditioner may help.