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"Ground lifting" to eliminate noise from Computer

Discussion in 'Recording' started by Ardroth, Apr 11, 2007.

  1. Ardroth

    Ardroth Guest

    I heard a hum/static through my monitors and headphones when using my Firepod... After a while, I eventually traced the problem to the power adaptor for my Laptop. When plugged in, there is a hum, and when not plugged in there isn't. This must be due to the ground... therefore, I'm trying to figure out the best way to solve this problem. I know that Ground lifting is generally dangerous and not recommended. IF anyone has a tip on how to keep my computer plugged in and to eliminate this hum from the adaptor (ground) that would be helpful. Thanks.
     
  2. JCarlo

    JCarlo Guest

    Some ideas:

    Plug the power adaptor to different ac outlet than the rest of your gear.

    Turn the power adaptor 180 degrees and replug it. Sometimes it works.

    Use a good UPS and plug your laptop's power adaptor to the battery bakup outlets. You should do this anyway.

    Try Ebtech's hum eliminator.

    Try a balanced power supply.
     
  3. Ardroth

    Ardroth Guest

    I tried plugging it into my power conditioner and my regular surge protector, and I still go the same hum.

    I turned the power adaptor - doesn't do anything.

    What is a UPS? I can only think of "universal power supply". How do you plug the adaptor to the battery backup outlets?

    I'll look into the Ebtech.

    Please elaborate on a balanced power supply.

    I'm still new to DAW recording, so forgive me for my ignorance on some of your suggestions.

    Thanks!
     
  4. Link555

    Link555 Well-Known Member

    It might be the switching power supply in your computer, which can cause a lot of trouble in the audio band.

    Here is some useful background info:
    http://www.epanorama.net/documents/groundloop/home_solving.html

    I believe the Firepod is not connected to earth; does it have a wall wart transformer with only 2 prongs?

    Does you laptop power supply have an earth connection (2 prongs or 3?)?

    Do the monitors have an earth connection?


    Here is a line isolation transformer (best solution):
    http://www.hammondmfg.com/171.htm
    This will isolate your PC from the other circuits.

    or this -which may not be as good but much cheaper: HUMplug-e
    http://www.21best.com/21_best/electronic/security/video/filters/for_sale_.html

    Best of luck.
     
  5. Ardroth

    Ardroth Guest

    The HUMplug-e is what I would need. The first one (isolation transformer) looks good, but a little bulky... it would be a pain to carry around with my portable DAW. Also, I can't seem to find a price on that one (unless I called).

    To answer your questions:
    The firepod is not a wall-wart. It is a 2-prong "central station" power supply seen here: http://images.google.com/imgres?imgurl=http://www.presonus.com/store/images/PSfirepod.gif&imgrefurl=http://www.presonus.com/store/index.php?cPath=28&h=68&w=73&sz=3&hl=en&start=6&um=1&tbnid=rtZJnFHZMPaFZM:&tbnh=65&tbnw=70&prev=/images?q=firepod+power+supply&svnum=10&um=1&hl=en&client=firefox-a&rls=org.mozilla:en-US:official&sa=G

    My laptop power supply is a ground connection (3 prong).

    My studio monitors are both 3-prong (however they are not the problem - only the laptop creates the ground loop when plugged in).

    Thanks.
     
  6. Link555

    Link555 Well-Known Member

    Thanks Ardroth,
    Ok so the firepod has a floating chassis. Which mean there is no earth connection, IE no third center prong.

    All and all I think the HUMplug-e, should work, but if doesn't the Hammond iso-transformer will.
     
  7. Ardroth

    Ardroth Guest

    Yeah, I agree... I ordered the Ebtech HUM-X from Amazon.com for $60... hopefully it will solve my problem. Thanks for the help man.
     
  8. Jbrax

    Jbrax Guest

    Ive read the same problem with the firrepod power supply also
     
  9. Link555

    Link555 Well-Known Member

    No problem Ardroth. Good luck!
     

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