What would be the source of my speakers humming?

April 2, 2007 8:39 PM

What would be the source of my speakers humming?

There is nothing connected to my cheap amplifier other than the speakers via their cables. Surrounding devices have been turned off at the wall. I have also tried another set of speakers that are brand new. Nothing has worked thus far to identify the source.

posted by sjvilla79 to Technology (15 answers total)

This thread might help.
posted by null terminated at 8:45 PM on April 2, 2007

Response by poster: I forgot to add that the hum only occurs when the amplifier is turned on. Sorry about that.
posted by sjvilla79 at 8:50 PM on April 2, 2007

Well, maybe that cheap amplifier isn't isolating its transformer very well and you're hearing a 60hz AC hum. Alternatively, maybe some other device in your household is generating more noise on the AC line than your amp can filter. Or, finally, I'm assuming you mean the surrounding devices aren't connected to your amp and/or they are unplugged from the wall, but, if not, then you may be getting the noise from a ground loop.
posted by Ethereal Bligh at 9:24 PM on April 2, 2007

Is it grounded? Sometimes cheap-ass amps forget to include a third prong on their plugs and need to be physically connected to something earthed.
posted by klangklangston at 9:34 PM on April 2, 2007

Inputs to amplifiers are often set so that if there is nothing plugged in, the inputs are grounded. Otherwise, the inputs are "floating" and can cause a hum. If your inputs are grounded when empty that could be the problem. Or, if you have something plugged in, but not on, same thing (with something plugged in, but off, the normally closed circuit tying the input to ground will be open and floating)

In addition it could be many many types of RF interferance. Try rotating the direction the amp faces and see if that makes any difference, or move it around.

It could also just be a noisy power supply. The power supply's job is to turn 60 Hz AC into DC. It usually does this through a combination of rectifying and filtering, but depending on how good (or bad) the filtering is, you can have considerable amounts of AC hum remaining.

The speakers are almost certainly not the source.
posted by RustyBrooks at 9:35 PM on April 2, 2007

I should have said, if your inputs are NOT grounded when empty, that could be the problem.

By the way, one way to semi-diagnose this is to plug in one end of a cable into the amp's input, and leave the other input free. Touch the tip of the cord - does this help (when you touch it, you are grounding it)
posted by RustyBrooks at 9:40 PM on April 2, 2007

It could be a ground loop or otherwise noisy power. Maybe get a Power Conditioner from your local pro-audio shop or get a "ground loop isolator" from your local Radio Shack.
posted by fvox13 at 9:56 PM on April 2, 2007

Response by poster: Thanks for all the feedback. It is grounded. I think it might be noise from the power supply as I've tried all other things. Drat.
posted by sjvilla79 at 10:49 PM on April 2, 2007

Have you looked at other noisemakers? I have a halogen desk lamp that has a dimmer and it made my computer speakers hum until I relocated the lamp cord. Flourescent fixtures can cause a hum as well.
posted by SteveInMaine at 3:29 AM on April 3, 2007

Best answer: The source of your speakers humming would be your cheap amplifier.
posted by flabdablet at 4:35 AM on April 3, 2007

Have you tried using an outlet in another room? You might just have crappy wiring in that outlet (or the whole place). I had a similar problem at an apartment of mine with one specific outlet that made my subwoofer hum.
posted by Gamblor at 9:01 AM on April 3, 2007

Although it may not be possible if you have a 3-prong plug, or one with a wide prong that fits only one way, it sometimes helps to reverse the power cord orientation. I always take sheet metal shears and remove the wide ears, since the wall receptacle itself may be wired backward.
posted by KRS at 11:13 AM on April 3, 2007

1. invite a friend over
2. have friend hang out by the speaker while you unplug everything else in the house individually until you discover the source of the hum
3. put a ground lifter on whatever is causing the hum, if it won't cause any problems.

I agree with all the recommendations so far, but there's some stuff even power conditioners can't fix. I have multiple furman PL-Pro Rs and my wife's electric hair iron still causes the studio monitors to make weird noises...even when they are turned off!
posted by Señor Pantalones at 11:13 AM on April 3, 2007

Response by poster: I took the amplifier back to the shop. Clerk says to me that this isn't the first time this item has been returned with the same issue. I got a credit. Thanks again for the help here. I'll know better the next time I think of buying a cheap and crappy amplifier.
posted by sjvilla79 at 7:28 AM on April 5, 2007

Cheap and crappy amplifiers are perfectly fine if you don't really care how good they sound; they're OK for PA systems or watching YouTube or enjoying Jimi at high volume. If you want to own something that actually sounds good, though, your best bet is always to listen to it before you buy it, preferably in a quiet environment.

If you've bought something that sounded really good in the shop but it hums like a bastard at home, then would be the time to start wandering around unplugging other things.
posted by flabdablet at 4:23 AM on April 6, 2007