Earthing kit

Discussion in 'Hi-Fi Stereo Systems & Separates' started by cest moi, Feb 20, 2013.

  1. cest moi

    cest moi
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    I have a fair bit of av equipment and I've never bothered to attach the earth screws to anything, however, I figure I should.

    Do I just run a wire between the screw and the earth pin of a plug?
     
  2. stevelup

    stevelup
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    Don't do it. You'll just introduce ground loops and create more problems than you're solving.

    Unless you have a specific problem?
     
  3. cest moi

    cest moi
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    No problems really.

    But while I'm here, I do get a hum from my subwoofer when there is no signal coming in eg. when my AV receiver is turned off but subwoofer is turned on...
     
  4. stevelup

    stevelup
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    Subwoofers are frequently problematic for several reasons.

    1) they are often plugged into a completely different electrical outlet to the rest of the kit
    2) they are often the only long run of an unbalanced signal
    3) 50Hz mains hum is particularly noticeable because it is the perfect frequency for a sub to reproduce

    First thing to eliminate is a ground loop. Is your sub plugged into a different mains socket to the rest of your kit? If so, use a mains extension lead and plug it into the same socket as your amplifier. See if the hum goes away.
     
  5. cest moi

    cest moi
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    It's in a different socket. But the only kit in the room is av kit and the room has its own ring main to the rest of the house and its not really practical to try an extension lead as the rest of the kit is the other side of the room.

    It feels as though the amp may be giving out a signal when off. I'll double check but I've got a feeling that when I unplug the signal cable from the amp the hum stops.

    The hum; annoyingly; is a higher enough signal to stop the subs auto off function from working.

    Sorry I'm quite tired so not sure how much sense that made.
     
  6. cest moi

    cest moi
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    Rereading that, it would be practical to plug it into the same socket for the purposes of a test.
     
  7. cest moi

    cest moi
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    Ok.

    I get hum:

    When amp is off and signal cable is plugged in to both sub and amp I get quiet hum.

    When amp is off and I disconnect cable from amp I get loud hum.

    When signal cable is disconnected from sub I get no hum.

    When signal cable is connected and amp is turned on I get no hum.

    Last thing I want to check but ran out of time to is whether the auto off on the sub kicks in when the amp is on but there has been no signal for a while.
     
    Last edited: Feb 26, 2013

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