Trying to fix sub woofer humming noise.

Fruhstuck

Honorable
Nov 28, 2012
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10,510
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Hello,

I recently moved back into a college apartment. When I plugged in my Altec Lansing VS4121BLK speakers to listen to some music. I noticed a low humming or buzzing noise coming from the sub woofer. I went online and started trouble shooting I read a few articles about something called ground loop issues. However, I'm not sure if this is the issue with my speaker system. I tried plugging it into various different outlets and power strips and it still makes the noise. so I started to unplug wires from the back of the sub woofer one at a time.

Bear in mind that this sub woofer connects directly to the wall from itself to get power using a two prong outlet. The rest of the audio system connects to the back of the sub woofer. It has two speakers each one has its own wire that connects to the sub woofer. the right speaker has the power button for the system, volume control knob, treble, and bass control knobs. When you turn the bass knob to far left or right the hum is very noticeable and if you leave it in the center it is close to unnoticeable.

Back to talking about removing the cables one by one. When I leave the system plugged in and remove the right speaker connector from the back of the sub woofer the humming noise goes away completely. I don't know what this means but there is power going to the system and I think this eliminates the possibility of a ground loop issues since all I did was remove the right speaker connection. What could this be an issue of and how can I solve this humming noise with my sub woofer?

Thank you,
Fruhstuck
 

makkem

Distinguished
Right,the subs not grounded(2 pin plug),so its not a ground loop.
If you pull out the input plug is the hum still there?
The reason the hum is through the sub and not the speakers is that there is an audio filter that puts low frequencies to the sub and higher frequencies to the speakers,the hum will be low frequency (50-60Hz)
Looking at that system it appears that the right speaker controls the system so disconnecting it effectively turns the system off.
If you still get the hum with no input connection I would suspect a power supply capacitor has failed,it may be worth a look inside to check for discoloration on any power supply components.
 

makkem

Distinguished
Hi
to be a ground loop problem one or more devices attached to the unit would have to be grounded,so try a battery powered source like a phone or ipad as a sole source and see if you still get a hum.
Does the hum come from both speakers or just the right speaker,and with the right speaker disconnected do you get hum free music from the left speaker.
Does the volume control affect the volume of the hum.
 

Fruhstuck

Honorable
Nov 28, 2012
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Well it doesn't plug into something like an ipod or at least I don't know how it would. The hum is coming from the sub woofer not the speakers.

Here's a picture of the back of the sub woofer. If I disconnect the right or orange labeled wire from the socket the hum goes away even if I leave the speaker power plug and the other two wires plugged in.

http://images.highspeedbackbone.net/SkuImages/gallery/large/A162-2114-09.jpg

Here's also another link with a better picture and information on the system.

http://www.newegg.com/Product/Product.aspx?Item=N82E16836113138

Thanks

Hopefully this helps explain the situation a bit.
 

makkem

Distinguished
Right,the subs not grounded(2 pin plug),so its not a ground loop.
If you pull out the input plug is the hum still there?
The reason the hum is through the sub and not the speakers is that there is an audio filter that puts low frequencies to the sub and higher frequencies to the speakers,the hum will be low frequency (50-60Hz)
Looking at that system it appears that the right speaker controls the system so disconnecting it effectively turns the system off.
If you still get the hum with no input connection I would suspect a power supply capacitor has failed,it may be worth a look inside to check for discoloration on any power supply components.
 
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