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Passive sub hum

Discussion in 'Subwoofers' started by boxtel, Mar 30, 2005.

  1. boxtel

    boxtel
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    I am based in South Africa, and have recently bought the Pioneer HTZ-323 all-in-one HT system, which is equivalent to the DCS-323 in the UK. It has a passive subwoofer. When I switch on the unit, even without a disk in it, there is a hum from the subwoofer which is audible with the volume less than half way, and increases as the volume is increased. The humming stops if I disconnect the sub or mute the sound. I have checked the wiring, and tried repositioning the sub, but this has made no difference.

    I have read most of the threads on this forum related to this problem, but they mostly seem to relate to active subs. While I don't fully understand ground loops and isolation, I assume this would not apply to me because there is only one power source to the main amp. In any case, the sub is made of wood and plastic, so I don't think there is any metal to ground it to the amp.

    I am new to the HT arena, and my first experience is somewhat disappointing, so any suggestions or advise would be welcome, and highly appreciated.
     
  2. JBL 4645

    JBL 4645
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    Hallo there mate sounds like it my be the mains transformer that converts the electrical power down to power the sub woofers amplifier…then if it not that it may be the wiring…try some new wiring as the wiring may be faulty or try the rca phone cable as it may have a broken ground connection of some kind that’s producing the humming sound.

    Also I had a hum sound on my home cinema set-up that was solved by grounding on of the graphic equalisers to the amplifier…I not saying you may have a similar problem there but try taking a long piece of wiring and attaching it to the anything that as a screw on it to see if the humming disappears or it maybe the earth connection on the mains plug on one of many parts of the set-up that’s the best I can do to help hear.

    Oh one more thing manufactures make mains humming isolators that supposable reduce this type of problem…and it’s fairly common too.

    So let me know the out come what you did to solve the funny?

    Funny is a term that NASA uses when something is not working correctly.

    I’m a former cinema projectionist.

    Cheers

    Ashley…
     
  3. alexs2

    alexs2
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    Worth noting,Ashley,that boxtel's system has a passive sub,as he clearly states in the first line of his post.

    This means that any hum from the sub has it's origin in the 323's amp section,and the problems will need to be dealt with there,and not by grounding a non-existent power amp in the sub,which as he also says,is made of wood and plastic.

    As to solving the problem....does the hum occur with all inputs to the system,and have you tried adding an earth to the 323 itself,given that many such systems are not supplied with a 3 pin wired plug,just a simple 2 pin system,relying on double insulation in the amp itself.
    This may help,as may help,as may trying moving the 323 away from any other sources of electrical interference,which may also be a cause of hum.

    I would begin by ensuring the 323 is adequately earthed initially,and then move on to removing other sources of interference.
     

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