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2.1 speaker system making bumping noises like heartbeat when sound not playing
2.1 speaker system making bumping noises like heartbeat when sound not playing
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Old 12th February 2017, 05:42 PM   #1
sonyzz is offline sonyzz  Lithuania
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Default 2.1 speaker system making bumping noises like heartbeat when sound not playing

so as the title says i have system of 2.1 speakers with computer but when playing nothing they make sound similar to heart beat, but its not constant like 60hz sound or sound every one second, it is more like bump bump bump then silence for some seconds then bump bump then silence then bump - silence - random bumping, but when there is no sound played, when i play sound there is no bumping, but there is when i play very low on volume like 5-10 percent - there is bumping noises
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Old 12th February 2017, 07:38 PM   #2
tomchr is online now tomchr  Canada
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That could be the biasing of the output stage of the amp. Does the problem occur in all channels or just in one?

It could also be a power supply issue. If the problem is present in all channels, that'd be my starting point. If you have an oscilloscope, I suggest looking at the supply voltage when the system makes the bumping sound.

Tom
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Old 12th February 2017, 08:15 PM   #3
sonyzz is offline sonyzz  Lithuania
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Quote:
Originally Posted by tomchr View Post
That could be the biasing of the output stage of the amp. Does the problem occur in all channels or just in one?

It could also be a power supply issue. If the problem is present in all channels, that'd be my starting point. If you have an oscilloscope, I suggest looking at the supply voltage when the system makes the bumping sound.

Tom
its present in all channels, but mostly subwoofer is making that heart rate sound, i dont own oscilloscope, could it be because the speaker input wire from pc is next to mains wire to pc? it was making same sound when i bought it from friend who didnt liked the sound even thoose were new speakers
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Old 12th February 2017, 10:21 PM   #4
tomchr is online now tomchr  Canada
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If you had 50/60 Hz hum, it could be because of a loose ground or the proximity to the mains wiring (though that's unlikely anyway).

The thumping is probably a power supply issue. Try disconnecting the speakers from the PC and short the three input connections (tip, ring, and sleeve) on the input jack together. If you still have the thumping, the issue is due to something within the speaker/amps. My guess is that it's something within the power supply.

Tom
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Old 12th February 2017, 11:17 PM   #5
MAAC0 is offline MAAC0  Portugal
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Try this

With the amp powered on try to switch a nearby incandescent or fluorescent lamp.
Do you hear switching thumps ? If yes it could be some bad filtering at the PSU and so you get random interference from mains. My Logitech Speakers do it but it is more like "Sparkling".
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Old 13th February 2017, 11:22 AM   #6
AndrewT is offline AndrewT  Scotland
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I wonder if it's an SMPS switching OFF/ON repeatedly when current demand is very low?
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Old 13th February 2017, 12:32 PM   #7
basi is offline basi  Croatia
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Believe it or not i have many cheap computer speakers in last few weeks with similar problems.Many of them are almost new.The problem is signal input and they all dont have input rc filter/low pass filter.
Picking some kind of strange signal from atmosphere i cant explain it.

Low pass filter has solved all problems.
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Old 13th February 2017, 10:46 PM   #8
Arty is offline Arty
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i'd suppose it would be really dirty, but you could rig up something like 400+nf cap in series with the input of the amp and a 2-300pf ceramic from input to signal ground, surely its not something you want to keep there as it would act as a tone controll dependent on the volume pot, but for testing it should do fine i guess..

however i had a car amp doing that and it was a bridged class AB one, it had one of its outputs shorted and when no input it had it made a "thump" sound few times a secund, not sure why it did not do that when it has a live signal...

so those are 2 things i might try.
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Old 14th February 2017, 09:55 PM   #9
MAAC0 is offline MAAC0  Portugal
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Basi

Cellphone Microoven Wifi you name it. ... and don't forget also the quasars pulsars magnetars and black holes light-years away ...
I would try perhaps another PSU. (Ordinary tranny with bridge rectifier and large capacitance say 2200 or 4700 uF)
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Old 14th February 2017, 10:01 PM   #10
MAAC0 is offline MAAC0  Portugal
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I remember I had a sound isolator device (a box with some tiny transistor radio or phone line output transformers) when connected to two RCA inputs with pot at low volume it behaved the same way .. king of motorboating...
Try a small 470 to 1K resistor in series with the input lines or some 10k shunts on the inputs.
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