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  1. #1
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    Unusual sound problem

    Alright. This problem started about a year ago and only recently did I decide I have had enough.

    Overview: The problem has to do with interference that is being produced by what seems to be the computer and coming out thru my stereo system (Yamaha receiver, 2 Boston Acoustic speakers, and a Velodyne subwoofer) through 2 methods of sound output (Xitel Hi-Fi link and triple shielded oxygen free high grade 3.5mm to 2 RCA cable).

    I had initially used a Xitel Hi-Fi Link, connected from USB to the component to a 3.5mm to 2 RCA cable, which was plugged into the AUX input on my Audio Receiver. One day I noticed a buzzing/humming coming thru the speakers when there were quieter parts/empty spaces in songs; it has progressively gotten louder. I thought that I had diagnosed the problem being the Hi-Fi Link and turned to a new way of playing music thru my stereo. I realized I could plug the 3.5mm to 2 RCA into my sound card and it will also play. Unfortunately the interference still was coming thru the speakers. So the Hi-Fi link is ruled out as the problem. What is unusual is that the interference is still noticeable even when the computer is turned OFF.

    I then turned to my laptop, plugging the audio cable into the headphone jack and then playing a song. The music came thru crystal clear with not the slightest hint of interference (same cable, plugged into same input on receiver, different computer). So this is where I am stuck. I have diagnosed that the Hi-Fi Link, Cable, and Receiever all are not the cause of the interference meaning that it most likely has to be something in the computer that functions even when turned off.

    Just something to emphasize, nothing has to be playing on the computer, no applications have to be open, as long as I am on AUX on my receiver and the connection from PC to Receiver is established, interference is very noticeable

    This is where I turn to you.

    Thank you,

    -Ben

  2. #2
    4 Star Lounger
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    Re: Unusual sound problem

    This sounds like a standard ground loop problem. The first thing to check is whether the hum is present if the computer and receiver and both plugged into the same grounded receptacle. If that does not fix it, try disconnecting the antenna input from the receiver. Your antenna ground and your power ground may be at slightly different potentials. If this eliminates the hum then you can either run your system this way or get an antenna isolator. Hopefully this will get you started on a solution. Let us know what you find.

    Paul

  3. #3
    Uranium Lounger viking33's Avatar
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    Re: Unusual sound problem

    Ben,
    Please be a little more specific as to what you mean by "interference".
    Static? Hum? Background audio? Or what? I know you said buzzinghum.

    I would be more likely to suspect some sort of feedback through your AC power line. Have you tried to switch one of the units to another power outlet? I would hope none of these are on a "extension" power cord rather than a well grounded outlet.
    BOB
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  4. #4
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    Re: Unusual sound problem

    Paul:

    When you say grounded receptacle are you referring to the wall's electrical outlet? And when you are referring to the antenna input from the receiver, are you referring to the radio antenna? You're lingo is above my knowledge of electrical components. Thanks.

    -Ben

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    Re: Unusual sound problem

    I want to emphasize the fact that the audio receiver doesn't play a role in the interference problem because there is no buzzing when the laptop is connected to the receiver.

    I did another test where I plugged my laptop into the same surge protector as my pc to see if there was a grounding problem and there was NO interference.

  6. #6
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    Re: Unusual sound problem

    Yes by grounded receptacle I mean an electrical outlet.. Try plugging the receiver and the computer into a single electrical outlet. The antenna I am referring to is the radio antenna - try disconnecting it. However, not knowing your setup you may also have some TV antenna hooked up as well, so remove any and all antenna connections from the receiver and check for noise again.

    Paul

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    Re: Unusual sound problem

    We can get into this later, but if it is a ground loop problem we are dealing with then the audio receiver is definitely, positively a part of the problem. The lap top is isolated from the power system so in that hookup you do not have two, possibly different, grounds. With the receiver and the other computer, however, you do.

    Paul

  8. #8
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    Re: Unusual sound problem

    Bob:

    The buzzing sounds like a swarm of bees maybe would, fairly consistent thru both speakers and sub woofer, accompanying the buzzing is an occasional series of short pops which eventually overwhelm the initial buzz, but occasionally go away. I would say the noise is unlike static and definitely not background audio. If you were to take the metal part of the audio plug and touch the metal on the back of the computer, the interference noise coming thru the speakers is just like that, but a little quieter.

    Both components (PC and Receiver) are plugged into separate surge protectors on opposite sides of the room.

  9. #9
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    Re: Unusual sound problem

    I was going to move my PC to the other side of the room to plug it into the same outlet as my receiver when I noticed something unusual. Even with my PC unplugged from the surge protector the interference is still just as prevelant. So with no power going to the PC at all, I don't believe it can be a grounding problem. If you would still like me to do the same-ground test I was about to do let me know.

  10. #10
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    Re: Unusual sound problem

    If your have the monitor plugged into the surge protector and the signal cable from the monitor plugged into the PC then your PC is still grounded, so yes it is probably a useful test to move the PC and any of its connected components to the wall outlet that the receiver is plugged into. By the way all of this is to simply decide if it is a ground loop problem. What we do about it is another matter.

    Paul

  11. #11
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    Re: Unusual sound problem

    I moved my PC across the room and plugged it into the same surge protector as my receiver and the humming is still present.

  12. #12
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    Re: Unusual sound problem

    Ok, have you also disconnected any antenna connections to the receiver ?

    Paul

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    Re: Unusual sound problem

    You might try opening the PC's case and re-seating all of the peripheral cards as well as making sure all the cable connections are tight. Leave the computer plugged in to a wall receptacle and touch the metal casing before checking to ensure that any static charge you may be carrying is safely discharged. Pull the cards from their sockets and put them back in; you may be a victim of heat affecting the connections in the slots. Whatever the case, it certainly sounds like something electrical is causing the problem. How old is the computer that generates the noise?
    -Mark

  14. #14
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    Re: Unusual sound problem

    I just want to let everyone know the problem was resolved due to a 3rd party person coming in and diagnosing it. It turned out to be the TV I had plugged into the receiver was apparently sending a signal back through the receiver into the computer, or something along those lines. So it was a grounding problem just as a result of my TV's influence.

    Thank you for your help.

    -Ben

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    Plutonium Lounger Leif's Avatar
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    Re: Unusual sound problem

    Thanks for posting back with the solution!

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