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60 hertz hum

Discussion in 'General Electronics' started by Dennis, Jan 3, 2006.

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  1. Dennis

    Dennis Guest

    I'm running the output of my computer to my stereo aamplifier.
    I'm getting an annoying 60Hz hum through both speakers. This
    occurs with all inputs and outputs muted. If I unplug the plug from
    the back of the computer the hum stops. Help please,

    Dennis
     
  2. Sjouke Burry

    Sjouke Burry Guest

    Make sure, that both your computer and your stereo are connected
    to ground. The netfilter in your computer will otherwise dump a
    filtercurrent along your audio path ground.
     
  3. More precisely, make sure that your stereo amplifier and your computer
    are connected to the same ground. Even a few millivolts of AC
    difference in ground potentials can cause lots of 60 Hz hum.
     
  4. tempus fugit

    tempus fugit Guest

    Sounds like ground loop hum. Try plugging your stereo into the same outlet
    or power bar as your computer and see if it goes away.
     
  5. CJT

    CJT Guest

    If you have cable TV in any way connected to either your stereo or
    computer (e.g. via a cable modem), disconnect it and see whether
    the hum stops. If it does, you know the culprit.
     
  6. Jasen Betts

    Jasen Betts Guest

    what about with the computer turned off (but plugged in)?

    if it's still there the noise is comiing from the cabling (called a gound
    loop)

    one thing that helps sometimes is to ensure that the sterio and all the
    devices that are connected to it and (subwoofer, DVD player) and any devices
    that are connected to them... are all connected to the same electrical outlet
    (and to the same filter if any)

    if that helps there's a relatively inexpensive device called a audio
    isolating transformer that'll probably kill the hum and let you return the
    power cabling to its original configuration.

    another option would be to go with a non-conductive connection (like fibre
    optic if your sterio and sound card support it)

    Bye.
    Jasen
     
  7. Sounds like you've got a ground loop. You could try removing the screen
    connection on the interconnect. Or buy a transformer designed to prevent
    ground loops from a car audio place.
     
  8. Alan Holmes

    Alan Holmes Guest

    But only if you live in the US of A, if you live in other parts of the
    world, it will be 50 hertz.

    Alan
     
  9. kip

    kip Guest

    R you sure of that statement ?
     
  10. Neither. The hum you hear in the UK is actually 100 Hz.
     
  11. sofie

    sofie Guest

    Alan:
    Gee.... what about Canada, Japan.... and other countries beside the USA that
    run 60 Hz power???
    --
    Best Regards,
    Daniel Sofie
    Electronics Supply & Repair
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  12. Alan Holmes

    Alan Holmes Guest

    Only backward countries use 60 Hz!:)-)

    Alan
     
  13. Alan Holmes

    Alan Holmes Guest

    Not 100%, no!

    Alan
     
  14. Something you might try (although you didn't hear it from me) is completely
    disconnecting the ground pin on your computer. You didn't mention what kind
    of computer you're using, but if it's a laptop, grounding isn't too
    essential. (In fact, having a permanently lifted [broken off, actually]
    ground pin on mine has several times saved my laptop from almost certain
    major damage when connected to equipment with a ground fault - a common
    problem in my line of work.)

    In my case, I'm also using a laptop for a home music recording studio (I
    know, not the best choice, but it was sitting around...). All of the audio
    I/O is via an external high-quality device, but ground loop hum was killing
    me, *even though everything was plugged into the same outlet strip*.
    Breaking off the computer's power supply ground pin completely solved the
    problem.
     
  15. CJT

    CJT Guest

    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    In other words, you recognize what a bad idea this is.

    is completely
     
  16. sofie

    sofie Guest

    CJT:
    Some years ago when I was in the pro-audio installation business for an on
    the road entertainment company, us installation techs would always carried
    about a dozen "u-ground" 3 wire to 2 wire ground adapters in our tool boxes
    so the ground could be temporarily "lifted" on various pieces of gear to
    eliminate ground loops and the subsequent hum problems. (don't cut off
    ground pins on the plugs of equipment) Usually the problem would originate
    because remote equipment was on a different circuit from the breaker box and
    was located some distance from the main head-end gear.
    --
    Best Regards,
    Daniel Sofie
    Electronics Supply & Repair
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


     
  17. Crikey. You'd have been shot in the UK. ;-)

    1:1 repcoils are the correct way with balanced pro audio gear. You
    *really* shouldn't mess with safety earths.
     
  18. sofie

    sofie Guest

    - - - - - - - - - - - - - - - -

    "crikey"

    exclamation UK OLD-FASHIONED INFORMAL
    an expression of surprise
     
  19. Ken Weitzel

    Ken Weitzel Guest

    YIKES! :)
     
  20. sofie

    sofie Guest

    Ken:
    I have traveled the world over..... been to the UK many times on business
    trips, personal vacations, etc.... but I had never heard the work "crikey"
    until today.
    How about up in Canada ?? Have you?
     
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