Why does my stereo screech at certain pitches?

July 25, 2005 1:48 PM

I recently moved my stereo to a new location. After I reassembled it, it started making screeching noises whenever a certain pitch is hit.

The noises are only made by one speaker. It produces an eerie static when a high pitch is reached by the music I'm playing. Here's a picture of the wiring in the back of the speaker, just in case that helps.

Any ideas how to fix this?

posted by agropyron to technology (11 comments total)

Screeching happens whether I'm playing a CD or using auxiliary input. It's the right speaker only in either case.
posted by agropyron at 1:49 PM on July 25, 2005

Does it sound like it could be vibration? Maybe there's something over by the right speaker that's vibrating? It could be a problem with the speaker, like maybe the cone got torn or a mounting screw got shifted during the move. Or it could be something got screwed up in the amplifier during the move.

To diagnose, try switching the output to speaker wires on the amplifier, so that the right output goes to the left speaker and vice versa. If the screeching shifts to the other side, the problem is in your amplifier. If it doesn't shift, try moving the right speaker a bit, or put it on some soft pad or something to dampen any vibration coming from it. If that doesn't help, I'd guess that it's inside the speaker. Can you take off the cover to look at the actual speaker? Look to see if anything is torn or loose.
posted by jasper411 at 1:57 PM on July 25, 2005

Ahh. Huh. I switched the wires, and now the screeching happens on the left side. So the amplifier's circuits got jumbled somehow, and now it's junk?
posted by agropyron at 2:12 PM on July 25, 2005

Could be that something just got shook loose during the move. Do you feel comfortable opening it up? UNPLUG IT AND GROUND IT - try to avoid touching anything, sometimes amplifiers have capacitors that will knock you flat even some time after the power got disconnected!!!!

But maybe you could scope out whether some wire or something just got knocked loose. But again! be careful when you open it, make sure that you are not completing a circuit!
posted by jasper411 at 2:23 PM on July 25, 2005

jasper411, you have scared me away from opening it. :P Thanks for the answers.
posted by agropyron at 2:27 PM on July 25, 2005

Junk might be a little severe.

Have you tried different inputs? What exactly is this amplifier that we are currently suspecting: a 2-channel amplifier, a stereo receiver, a two channel integrated amplifier, etc?

It sounds vaguely like an output transistor is fried. Somebody will still want it, but it may or may not be worth the money to have it repaired. jasper411 might have a point... It could be a bias jumper coming off, or it could even be that the bias pot slipped although that seems unlikely...

(Note: Bias is an adjustment made at a late stage of assembly in most old amplifiers, and many new ones. To facilitate the adjustment the circuit is left open, after the adjustment is made a jumper is placed to connect the circuit properly. The jumper might be similar to the jumpers you used to set on a motherboard, or you still set on an IDE drive for master/slave)
posted by Chuckles at 2:28 PM on July 25, 2005

try wiggling parts of the amplifier - the knobs, the plugs connected at the back. does anything trigger the funny noise (either when playing music or when silent, perhaps with the volume turned up)? if so, it's likely that it's been banged and has broken, partially, from the circuit board. you can open up the amp and resolder the part in question.
posted by andrew cooke at 2:30 PM on July 25, 2005

Sorry, I didn't mean to scare you. Many people (including myself) have been shocked and lived to tell the story.

If you (or a friend who's comfortable with it) unplug it, and just open it up without touching anything inside, you'll be ok. It's just when people start poking around with their screwdrivers or fingers without an awareness of what they might be touching that they place themselves at risk. If you like the amp, you could find an audio repair shop and take it in for an estimate.
posted by jasper411 at 2:32 PM on July 25, 2005

The amplifier in question is an all-in-one CD player, radio, cassette player. It's got the main unit, the two speakers, and that's it. It doesn't have any knobs at all, just a flat wheel for volume, and some play/aux/radio buttons.

SO, given the possibility that it's not worth the money to fix it (the whole thing cost $150 or so)....

Does anyone have a recommendation for a good stereo system in the $100-$200 range? I'm clearly no audiophile, it should just sound nice and not look like a teenager's boom box. CD player, radio and aux-in are all that's necessary.
posted by agropyron at 2:35 PM on July 25, 2005

Check to make sure that your audio line inputs are in all the way and swap them as well,if they are the RCA type.
posted by hortense at 2:40 PM on July 25, 2005

To find a new one in that price range, I'd recommend you just go to some home stereo type store (chains like Circuit City or Best Buy are possibilities). Listen to different systems and see what you like.

To find combo players, you'll probably be looking in the shelf system category. Though I'm not sure you'll be able to find a combo with CD, casette, and radio without it being a boom box type thing. I've certainly seen CD and radio combo shelf systems, like this one for relatively cheap (though I have no idea about how it sounds).
posted by jasper411 at 3:09 PM on July 25, 2005