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Help me with the hum please!!

Discussion in 'Subwoofers' started by psychedelic, Dec 19, 2004.

  1. psychedelic

    psychedelic
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    Hi guys i have a B&W 5.1 system which is driven by Denon 1905. I have to say its fantastic but the only probelm is there is always a low hum from the ASW 600. Its not annoying me while I am playing something but quite noticeable during the gaps. Could it be due to my subwoofer cable, picking up interference from the mains cable. If so what will I have to change ? Changing the Subwoofer cable will be much easier as the ASW 600 mains cable is not a plug and play type !!
    Thanks for your suggestions :thumbsup:
     
  2. engaged

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    Could be an earth loop problem. Try this; take a trip to your local B&Q and get a few metres (however much you need) of green/yellow single earth cable and a mains plug. Connect one end of the cable to the casing (phono ground) on your Denon and the other end to the earth (repeat: EARTH!) pin of the plug, and plug it in.

    It worked for me.
     
  3. bob1

    bob1
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    An earth loop is when at least 2 items in the audio change are earthed ,earthing the amp won't help, the idea is to remove an earth thus remving the loop.Some subs have a ground lift switch to remove the earth in case of this problem, thats if it is a earth loop.
    Earthing the amp might help with buzzing if its not a earth loop.
     
  4. eviljohn2

    eviljohn2
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    Trying a different cable would be a good start if you've got something suitable available which you could try.
     
  5. xmb

    xmb
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    I assume that if you un-plug the audio input to your sub the hum is removed?
    (If not your sub is faulty!)

    I had a Sony 100Hz TV and this always gave hum problems on the sub (no other earths in the system, only the sub was earthed) due to high leakage currents.

    The problem was solved when I purchased a Plasma TV!

    You can buy hum removing devices from some places (basically both the signal and screen lead going to the sub are fitted with capacitors to break the ground loop) which may help.
     
  6. psychedelic

    psychedelic
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    Thanks for you advice guys!!
    Thats right If I unplug my subwoofer cable the hum goes away. My sony is 50 Htz and What Hi fi advices to keep the mains cable away from the subwoofer cable.
    I will try to sort out the earth before changing the cables
     
  7. engaged

    engaged
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    Well, maybe my problem wasn't earth loop then...?! :confused:

    The constant mains hum I had disappeared if I either removed the earth wire inside the sub's plug - or did as I've suggested to psychedelic. I figured that the latter was safer! But then if some subs have a ground lift switch to remove the earth, and removing the earth in my sub's plug did remove the hum, then maybe it was a form of earth loop problem...? (And earthing the amp did have the same result...?)

    Irrespective of this, for the princely sum of £1 or so it'd be worth giving it a go.
     
  8. longitude

    longitude
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    Replacing my signal cable with high quality one solved my hum problem at a stroke. I've never really believed in these hi spek cables in the past but I'm convinced now.
     
  9. avanzato

    avanzato
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    Yep. Do a search for Earth or Ground loop isolators they cost from £10-£30. Though I thought they used a transformer rather than capacitors, could be wrong on that.
    There's a lot of info out there about ground loops and how to hopefully stop them, the one common factor though is don't remove the earth from the plug. If you do remove it and there's a fault then the metal chassis will probably become live and/or the unit will earth by the next easiest route, the interconnect and your other equipment.
     
  10. bob1

    bob1
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    Your right about that, i was talking to one of the electrcians at work today about the humming problems and he suggested isolation transformers.
     
  11. bob1

    bob1
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    Isolators that use Low level at the sub line in might use capacitors.
     
  12. bob1

    bob1
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    I found this ,it might work.
     

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