What is a ground lift?

Discussion in 'Amps [BG]' started by Bassboy9764, Sep 8, 2010.


  1. Bassboy9764

    Bassboy9764

    Joined:
    Jul 31, 2010
    Location:
    Pittsburgh, Pennsylvania
    I recently played a show and the sound guy sent a line-out from my amp and asked if I had a ground lift. I said I didn't and he seem surprised for some reason and came over and confirmed that my amp (Ampeg SVT-4Pro) didn't have a ground lift.

    Ever since I've been wondering what the heck a ground lift is.
     
  2. CapnSev

    CapnSev

    Joined:
    Aug 19, 2006
    Location:
    Coeur d'Alene
    Typically amps have a switch for the DI that when switched on, or "lifted", can eliminate ground loop hum from the wall socket that makes a lot of noise.

    I'm surprised that your amp doesn't have one too.
     
  3. hall1k

    hall1k

    Joined:
    Jun 14, 2009
    Does the ground lift actually mean that the connection is no longer grounded? Cause that could be dangerous (tho maybe it doesn't matter at such low power levels)
     
  4. billfitzmaurice

    billfitzmaurice

    Joined:
    Sep 15, 2004
    Location:
    New Hampshire
    Disclosures:
    Owner, Bill Fitzmaurice Loudspeaker Design
    The lift disconnects the ground of the XLR out, not the A/C supply. Explained here:
    http://www.rane.com/note110.html
     
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  6. jazzblade

    jazzblade

    Joined:
    Jun 21, 2005
    Location:
    Northern Cal
    Yes Ground lift only has to do with the XLR out of your amp. In the case the recording console or PA mixer is on a different power circuit.

    The two electrical circuits have a different electrical ground point which causes ground loops. By lifting the ground (wire) on the XLR connection between you and the sound guy, you remove that different ground potential,from each other removing the hum.
     

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