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MJ Reference 100 help

Discussion in 'Subwoofers' started by daveb975, Oct 24, 2004.

  1. daveb975

    daveb975
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    I have has my MJ Reference 100 for about a year.

    I have recently noticed that when the frequency is set to 'LFE', I can hear a buzz from the built in amplifier. This buzz increases with volume. This does not happen when the crossover is set to any other level.

    Can nay other owners of this model confirm whether or not this is correct?
     
  2. hornydragon

    hornydragon
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    how long is sub lead and what sort of quality.... it may be picking up resonant mains hummm
     
  3. MuFu

    MuFu
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    The most likely culprit is a ground/earth loop problem - caused by your sub and receiver having paths to a common earth but at different potentials, or by one/both being double-insulated (i.e. having "floating" ground planes). Make sure they're plugged into the same mains block, if possible. No idea why it only happens in LFE mode, but this is a common observation.

    Search for "ground/earth loop, sub hum, ground/earth sub hum" etc - plenty of info in these forums already. You can probably solve the problem completely by electrically connecting the amp plate on the sub to the receiver's chassis using a length of wire. Perhaps a more elegant solution is to wire the shielding of an old phono lead to the earth pin of a spare mains plug. Plug it into a mains socket (turned off, just in case!) and the other end into the unused phono input on the back of the sub.
     
  4. daveb975

    daveb975
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    Thanks guys, I will check this out.

    I am using a 4m QED sub lead - far too long for my needs, but it came free with the sub.

    I will try the methonds suggested tonight. I guess that if the frequency of the hum is less than 100hz, it would only come through on LFE mode - or am I way off the mark here?!
     

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