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Thread: lifting ground

  1. #1
    New Member
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    Aug 2008

    lifting ground

    Hi guy, i seen people disconecting the ground of a balance cable to remove noise such as hum,hiss,ect...
    I want to know how does this work.

  2. #2
    Ground lift doesn't do anything for hiss. Its primary function is to remove a ground loop.

    When two pieces of equipment are grounded together by two different paths - most commonly a cable shield and an electrical ground via grounded plugs - a loop is developed. This forms a giant loop antenna which can pick up hum. Very high hum currents are developed in the ground circuit, and these can get into the audio. The ground lift breaks the shield circuit at one end and elminiates the loop.

    The reason it's on a switch is that if an AC power line ground does not connect the two pieces of equipment - say, one of them does not have a ground pin on the power plug, like many CD players - then they should be connected together via the signal shield. So you have to be able to set it either way.

  3. #3
    Senior Member SC358's Avatar
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    May 2005
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    Since we're on the topic - anybody have a preference for wiring audio systems? And tell everybody why .

    Do you lift the source ground but connect the input ground or the opposite - ground the source signal and lift the input ground?
    Relationships are based on compromises - behavior accepted is behavior repeated.

  4. #4
    In the shop we have several dedicated 'lift' snake fan outs, they are all lifted on the Male XLR connectors, so the XLR is wired to ground (shield) at the source but lifted at the next device. I've not seen anything with the pin 1 lifted at the Female (source) end....

  5. #5
    I've seen both ways, and in each case the people involved are absolutely sure they're right. Maybe we should commission a study.

    My tendency is to ground at the receiving end because it's less likely to pick up RF interference that way. But then, I formed my habits back in the day when equipment was less RFI-protected than it is now. Even further back, when everything was floating-transformer-balanced, shields were irrelevant and many engineers did without them.

    Yes, I did say that. No, I'm not hallucinating.


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