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I'm hearing speaker hum in a stereo system that I recently hooked up. I can't pinpoint when the hum begins, but I've identified that turning certain lights off or on in the same room eliminates the hum.

I've identified two light switches that have this effect – not all switches in the room do. When turning one of these switches on or off I sometimes hear a 'pop'. The hum does go away after an indeterminate length of time if I don't touch any lights, but I haven't identified what might be coming on or off (appliances elsewhere in the house, etc.) that would cause this.

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Are any of the switches dimmers? –  bib Oct 23 '13 at 19:27
    
Yes there are dimmers in the room, but they don't seem to make the hum go away when I turn them off or on - and the hum seems to show up whether the dimmer switches are on or not. –  Robert Dyson Oct 23 '13 at 19:30
    
Do you have speaker wire running parallel and close (within a few inches) to power lines (like Romex)? –  bib Oct 23 '13 at 19:39
    
I do not – checked that! Thanks for the feedback (no pun intended). –  Robert Dyson Oct 23 '13 at 19:49
    
A long shot - some dimmers are active even when "off" (a trickle current runs through them). If the dimmers are on a separate line from the stereo, try turning off the breaker that powers the dimmers. If on the same line, rig an extension to the stereo from another circuit an pop the dimmer breaker. If that doesn't help, I'm voting for John's answer. –  bib Oct 23 '13 at 20:23
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1 Answer 1

up vote 5 down vote accepted

It sounds like you a ground loop issue. Take a look at "ground loop isolators" on amazon, best buy, etc... They might help the issue. This happens to me sometimes when I am putting a heavy load on a circuit in my house. (Vacuums, Hair Dryers, etc will do this)

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I would also recommend using a line filtering surge protector for the A/V equipment. All of my home theater and computer equipment is line filtered. Aside from helping with interference, it also helps protect AC/DC converters (even if a device lacks a power brick or wall wart, it still has one integrated in the device itself). –  John Gaughan Oct 25 '13 at 1:33
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