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How to remove buzzing sound in audio?

I have a Vista desktop PC and a small portable TV.  There is one set of external speakers that go into another room so I can hear either the PC or TV (depending if I have the TV plugged via its headphone jack).  The setup is like this:

- PC audio cord has Y adapter attached - male into audio card and two females out.  One female out to another Y adapter and one to a monitor with speakers.
- TV goes from headphone out to Y adapter with 3 females, which goes to external speakers and also to PC (so PC can play audio in ext speakers).
- Y adapter also goes to PC audio card but first meets another Y adapter, which allows PC audio to a monitor with speakers.

The problem is that once I plug the 1/8" cable into the TV, TV sounds drops to very low levels and I have a constant humm or low buzz.   To avoid this, I unplug the PC cable from the 3 female Y adapter.  But this means I must always plug in the TV and unplug the PC audio to the ext speakers to hear the TV.  Is there another way to set this up so I don't have the humm going on while the TV is also plugged in?

I've attached a drawing of the setup. PCTVAudio
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brettr
Asked:
brettr
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1 Solution
 
rickybsbCommented:
Cheers Brettr,

It seems that you are facing ground impedance difference between the devices.

Probably caused because the devices are not all grounded or because they use different electrical outlets. (different main electric phase).

rickybsb
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Michael-BestCommented:
Seems you are getting feedback by having two devices into the same speakers.
Also a Y-adapter is meant for multiple output and single input only.
See:
http://forum.allaboutcircuits.com/showthread.php?t=26659

But a simple way would be a toggle switch in the circuit.
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brettrAuthor Commented:
Using the diagram I have, where would the toggle go and which components need to be replaced?
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Michael-BestCommented:
You need an Audio A/B Switch to separate your two outputs.
At $6 and free shipping, this is as good as it gets:
http://www.meritline.com/showproduct.aspx?ProductID=40342&SEName=salar-sr1000-multi-function-audio-switch
Look at its wiring diagram and do the opposite.
PC and TV go to the female inputs speakers to the male (you do not need its mic connections)
So it allows you to select one source or the other, but not both.
Once again, it is a bad idea to connect two outputs together.
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