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Thread: Breaking earth loops

  1. #41
    Join Date: Jan 2009

    Location: Essex

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    I'm openingabottleofwine.

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    Quote Originally Posted by Stratmangler View Post
    I didn't post the picture of the isolating transformer box as a cure to anything.
    I was just showing a bigger, more complete version of the XLR model Ali posted.

    The cure is, as you've already pointed out, tracing the loop and then breaking it.
    I wasn't criticising the use of an isolation transformer, just pointing out that if mains hum has already got into the signal path, fitting a transformer downstream of the signal is not going to stop it.

    If however the mains hum is due to an earth loop, and it is not possible or convenient to fit earth lift resistors, then a 1:1 transformer placed in the signal pathway is a neat way to break the loop. But in adding an extra component into the signal path, the quality of the isolation transformer is important in respect of both frequency and phase bandwidth.

    I note the transformer unit is fitted with XLR connectors. I would have thought if using fully balanced interconnects between items having true dual-differential input/outputs, mains hum breakthrough would not be a problem.
    Barry

  2. #42
    Join Date: Apr 2016

    Location: Bishops Stortford

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    I'm Chris.

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    Just realised my computer that controls the miniDSP is plugged in a separate wall socket, so I can sit with it on my lap.

    I plugged it in the same place as the other five components and the earth hum has receded again. I think I can live with this ��

    Interesting topic. Thanks for your help.
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  3. #43
    Join Date: Nov 2008

    Location: Valley of the Hazels

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    I'm AMusicFanNotAnAudiophile.

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    Quote Originally Posted by bumpy View Post
    Just realised my computer that controls the miniDSP is plugged in a separate wall socket, so I can sit with it on my lap.

    I plugged it in the same place as the other five components and the earth hum has receded again. I think I can live with this ��

    Interesting topic. Thanks for your help.
    Laptop?
    Chris



    Common sense isn't anymore!

  4. #44
    Join Date: Apr 2016

    Location: Bishops Stortford

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    I'm Chris.

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    Quote Originally Posted by Stratmangler View Post
    Laptop?
    Yes the computer holds the program that controls the DSP in the bass circuit. Once the parameters are cemented I can power it with a 5 volt linear power supply.
    Source
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
    SW1X USB II
    SW1X DAC III Special
    Audiolab 6000 CDT transport
    Amps
    Pre amps -- Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired. And First Watt B1 active no gain buffer.
    Power amps -- Welborne 45 SET monoblocks 1.8W / Decware Taboo 6W / Elekit 300B TU-8600SVK plus further improved components 9W / ICE Power 1000W
    Speakers
    Highly modified Endorphin P17 open baffle speakers containing both vintage and modern alnico drivers and paper cones. All silver wired - 8" Cube Audio FC8 full range drivers and vintage 15" Altec VOTT 416 bass drivers. All sat on Townsend Audio Podium seismic isolation platforms.
    BK Electronics XLS400FF Sub.
    Cabling
    Silver mains cables, interconnects and speaker cables by SW1X
    Headphones
    HRT HeadStreamer and SennHeiser HD650 headphones

  5. #45
    Join Date: Nov 2008

    Location: Valley of the Hazels

    Posts: 9,139
    I'm AMusicFanNotAnAudiophile.

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    There is no mains ground continuity from the machine to the plug in the board.
    So there can't be a ground loop there.

    If plugging the laptop PSU has quietened things down then it's a good move, but I'd be bothered that a SMPS PSU was plugged into the same power block as the rest of my gear.
    Sticking a ferrite clamp us close to where the power cord plugs into the laptop PSU would reduce the effects of switching noise (aka RFI).
    We humans can't hear it, but amplification devices see it, and they're adversely affected by it.
    Chris



    Common sense isn't anymore!

  6. #46
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

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    Quote Originally Posted by Stratmangler View Post
    There is no mains ground continuity from the machine to the plug in the board.
    So there can't be a ground loop there.
    With mains connected equipment it is a safety requirement, that the chassis including its top and bottom side front and back metal work
    have access to safety ground. http://sound.whsites.net/articles/mains-safety.htm Whilst double insulation creates a different set of
    requirements, the majority of equipment requires chassis to be firmly connected to safety earth.

    Light Dependent Resistors happen to work exceptionally well to stop ground loop issues in audio equipment, having the side benefit
    of improving signal to noise ratio, and as a result the appreciation of music. An article here explores transistor based opto isolators
    that also have the same benefit : https://saaubi.people.wm.edu/Teachin...roundLoops.pdf

  7. #47
    Join Date: Nov 2008

    Location: Valley of the Hazels

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    Quote Originally Posted by Light Dependant Resistor View Post
    With mains connected equipment it is a safety requirement, that the chassis including its top and bottom side front and back metal work
    have access to safety ground. http://sound.whsites.net/articles/mains-safety.htm Whilst double insulation creates a different set of
    requirements, the majority of equipment requires chassis to be firmly connected to safety earth.

    Light Dependent Resistors happen to work exceptionally well to stop ground loop issues in audio equipment, having the side benefit
    of improving signal to noise ratio, and as a result the appreciation of music. An article here explores transistor based opto isolators
    that also have the same benefit : https://saaubi.people.wm.edu/Teachin...roundLoops.pdf
    It's a laptop computer.
    It's double insulated.
    Chris



    Common sense isn't anymore!

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