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Discussion Starter · #1 ·
I have my computer hooked up to my tv via HDMI. I have a 3.5mm cable from my computer sound card to the tv for audio.


I am getting a constant hum from the tv's speakers, though I can hear fine.


The weird thing is that if I unplug the cable from my computer and plug it into something else(mp3 player/cell phone) the sound goes away and I can listen to the mp3 player directly through my tv without problem.


So its not the cable, it's not the tv. It is baffling me.
 

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Discussion Starter · #2 ·
also, it buzz's when its not connected to anything at all.


the minute I plug it into the cell phone or mp3 player the buzz goes away.


But when I plug it into the output of the sound card, the buzz doesnt go away(though I can hear sound).
 

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If you hook up headphones to the computer, do you get the hum?


There could be lots of reasons for the hum. Do you have the audio from the computer "maxed"? Back it off a tad. Do you not have it high enough forcing the TV to be "up to high"?
 

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Discussion Starter · #4 ·
Headphones directly to the back of the sound card sound perfect.


Regarding the tv volume. The lower I put the volume the less the buzz, but at normal listening (a scale on my tv of 20 out of 100) it is noticeable and pretty annoying.


The computer volume has no bearing whatsoever on the buzz. The hum occurs without being connected to anything at all. If I rub or touch the tip of the 3.5mm I can hear a variation in the tone of the buzz.


I would just assume interference with something inside the tv... but again if you simply connect a device(mp3 player) it is crystal clear no feedback... the moment it is plugged in the jack.


So not the computer(it being out of the equation), not the cord(as buzz goes away when connected to mp3 or cell phone jacks), not the tv(again, problem solved when connected to mp3 jack)


I will paypal someone $20 if they can solve this for me, it's driving me nuts.
 

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Discussion Starter · #5 ·

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Discussion Starter · #6 ·
Ok...


I finally got something.


This 3.5mm cable from my computer to my tv is 50 feet and runs through the wall and through the ceiling to over side of room.


I have a dimmer light switch, connected to some lights by my desk and when I dim that the sound on my tv is going up and down in correspondence, its very clearly the cause.


So apparently I snaked that 3.5mm cable along the electrical line and that is what is making the noise.


When I turn the light off virtually all the noise goes away. When I turn it back on I get the loud buzzing.


So that's fine, that makes sense. What still DOES NOT make sense at all to me is when I connect the mp3 player or cell phone, the sound is crystal clear... meaning the light(on, off, or variably dimmed) and the electricity has no bearing any longer? How could that be?
 

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Discussion Starter · #7 ·
Ok...


My final synopsis.


The reason why my mp3 and cellphone are crystal clear across the wire is because they break the ground loop.


The computer is connected to the same electrical line as everything else in the room(tv, lights, dimmer switch)... they are all on the same grid. So plugging the 3.5mm into my computer is not actually addressing the voltage issues.


I will try a ground loop isolator.
 
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