Stereo defect
April 15, 2006 8:53 AM   Subscribe

Stereo: What makes it go pop?

I bought a used stereo amp/reciever a while ago. When it's on I'll hear a *pop* out of the speakers occasionally (more than once an hour, sometimes more than once every 10 minutes). This happens regardless of the input it's on (CD, video, etc).

What can I do to control this?
Is it dangerous to my other equipment (speakers?)
any idea why this happens?
posted by daver to Media & Arts (11 answers total)
i had a similar problem and after reading around at the time understood it was likely an electrolytic(?) capacitor gone bad, and that letting the electronics get warm, then spraying components with "cold air" (from a can) could help identify the culprit (no pop when the offender is cold).

in the end i got something else.

loud "hard" (high frequency) noises may damage your speakers (i think the tweeter coil tends to overheat). but i'm not sure a pop every 10 mins would do so, unless it was terrifyingly huge (and your amp's max power output was above or close to the speaker's max power rating).
posted by andrew cooke at 9:03 AM on April 15, 2006

My PC's speakers have started doing the something similar recently - I'm not certain, but I think it's since more taxi cab's have been in the area (they seem to drive past more now than they used to) - and they all have radio transmitters in them - I think mine is caused by them.
posted by Dub at 9:36 AM on April 15, 2006

My guess is that you're picking up noise from the power line, such as the spike when somebody's air conditioner/refridgerator compressor motor turns on. You might try a line conditioner.
posted by Rhomboid at 10:00 AM on April 15, 2006

since more taxi cab's have been in the area
pc speakers probably have an amplifier in the speaker itself. the wire to the speaker acts as an aerial, which picks up strong radio signals (like passing taxis); the amplified sound comes out of the speakers (in fact it's a bit more complex - the radio signal is at a much higher frequency, but poor/cheap design and non-linear amplifiers end up producing an audio signal). the same is unlikely in a "hifi" system because the amplifier is before the wire to the speakers, so the picked up signal is both smaller than the the signal being sent to the speakers and not further amplified, so remains inaudible (it is possible to pick something up in the internal wiring, or the cable between cd player and amplifier, but those cables/wires are shorter and the amplifier itself is probably better designed).

noise from the power line
this is usually the fridge/freezer - turn it off and see if you still hear the sound.
posted by andrew cooke at 10:03 AM on April 15, 2006

oh, could be air-con too, as rhomboid said. don't live ina country where those exist. sorry.
posted by andrew cooke at 10:03 AM on April 15, 2006

non-linear amplifiers - that's wrong, sorry. it's non-linear components, which you need, even if you make a linear amp.
posted by andrew cooke at 10:32 AM on April 15, 2006

Make sure all the inputs are secure, and the cables work well with other equipment. Is there any correlation with adjusting the volume, balance, whatever..

You say it happens on all inputs, but does it happen for many different sources? (are you just plugging your PC into different connectors, or are you trying a PC, a CD player, etc..)
posted by Chuckles at 12:49 PM on April 15, 2006

Heh...let me tell you about the time the capacitor in my ancient Nokia CRT discharged while sitting on a desk connected to a tower, 200 watt subwoofer and 150 watt monitors all silent but set to 98dB peak. Hello new CRT, video card, left studio monitor, and underwear.

Seriously though, you need a line conditioner between your power source and your amplifier so that it gets steady current. You also might check to see if there is any device on your circuit that is fluctuating in power consumption. For example, if your subwoofer or monitor are allowed to slip into low power mode, that could cause it. If not, something in the system is probably discharging small amounts of electricity periodically.
posted by mrmojoflying at 1:18 PM on April 15, 2006

Sounds like a bad capacitor or capacitors. Many repair folks just routinely replace all the electrolytic when an item is of a certain age. If you have access to an ESR meter (they are quite uncommon so I doubt it) then you can test them all. Refrigerant often works as well.
posted by caddis at 2:25 PM on April 15, 2006

You're sure you're not setting your cellphone near any of the equipment, right? Cell phones will certainly do things like what you're describing
posted by lockle at 4:59 PM on April 15, 2006

There probably isn't anything wrong with your stereo, from my experience. It's likely a refrigerator, furnace, or A/C switching on. I get similar pops on my speakers whenever the furnace clicks on -- and these are brand-new computer speakers.
posted by neckro23 at 8:47 PM on April 15, 2006

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