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  1. #1
    Wammer
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    Gents,



    Had an amp change recently and managed to introduce a mild ground loop between the pre/power. There was a mild but audible buzz emanating from the speakers, which was eliminated after I installed an isolator between them. However, it is a cheap component and not exactly a sophisticated audiophile solution and I was wondering what else I could do, other than have a 20p transformer between two expensive components? Is it dangerous to use a two-prong "cheater" IEC cable to the preamp, thereby removing the ground? What happens to the integrated phono stage ground in this instance? Does it even work?



    I haven't tried moving the components away from each other - apparently proximity related magnetic fields can also be an issue...



    Thanks,

    DT
    SACD: Marantz Pearl Lite
    Vinyl: Dynavector DV10x > Thorens TD309 > MF KW550 (JS Audio) > Wilson Benesch Square Two

  2. #2
    Too much time on my hands SergeAuckland's Avatar
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    Dynamic Turtle wrote:
    Gents,



    Had an amp change recently and managed to introduce a mild ground loop between the pre/power. There was a mild but audible buzz emanating from the speakers, which was eliminated after I installed an isolator between them. However, it is a cheap component and not exactly a sophisticated audiophile solution and I was wondering what else I could do, other than have a 20p transformer between two expensive components? Is it dangerous to use a two-prong "cheater" IEC cable to the preamp, thereby removing the ground? What happens to the integrated phono stage ground in this instance? Does it even work?



    I haven't tried moving the components away from each other - apparently proximity related magnetic fields can also be an issue...



    Thanks,

    DT
    Firstly, do NOT remove the ground (earth) wire. It's there for a very important safety reasons, and MUST be left in place.

    You can certainly try moving the components away, magnetic induction drops off with the square of distance, so even small increases in distance have large effects on induction.

    As to the quality of the transformer isolator, that may not be a problem:-

    At the radio station I work at, we had a problem with one of our presenter's laptop causing a buzz, soI bought a really cheap isolator (like £5) from CPC, cat No AV12774 to see if that cured the problem. It didn't but that's because the laptop's power supply turned out to be faulty.

    Anyway, before installing it, I measured the quality of the isolator, and found that when fed from a low output impedance into a high input impedance, and with up to a few volts on it, the performance was more than just acceptable. Do you hear any difference with the isolator or without it except for the buzz?

    If you do want to try something rather better, in terms of level capability and low distortion then I can recommend Sowter transformers, their 1:1 matching transformers are great.

    http://www.sowter.co.uk/specs/4652.htm

    alternatively

    http://www.sowter.co.uk/specs/3232.htm



    S.



  3. #3
    Price Discovery Bitch i_should_coco's Avatar
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    Post imported post

    Dynamic Turtle wrote:
    Gents,

    Had an amp change recently and managed to introduce a mild ground loop between the pre/power. There was a mild but audible buzz emanating from the speakers, which was eliminated after I installed an isolator between them. However, it is a cheap component and not exactly a sophisticated audiophile solution and I was wondering what else I could do, other than have a 20p transformer between two expensive components? Is it dangerous to use a two-prong "cheater" IEC cable to the preamp, thereby removing the ground? What happens to the integrated phono stage ground in this instance? Does it even work?
    Is it dangerous? Yes. If your equipment develops a fault, it could kill you. The correct way, without modifying your equipment is as you have done to use isolation transformers.

    Alternatively, have someone qualified modify your equipment to separate the safety ground (which MUST remains connected*) and 0v signal ground. This may not be feasible or sensible, though.


    I haven't tried moving the components away from each other - apparently proximity related magnetic fields can also be an issue... Thanks, DT
    If the isolation transformer fixes it, then it's not radiated, but indeed a ground loop.



    * Double insulated appliances don't have safety earths, don't need them, and would not suffer from a hum-loop anyway.


    Edit: Serge's Sowter recommendations would do the trick as well.


    CD players - computer audio for dummies.

  4. #4
    Moderator meninblack's Avatar
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    Ground loop/speaker buzz is a PITA.

    I get one now and again where ONE speaker buzzes terribly. It is intermittent, and usually starts up after I've moved something. Moving some different thing often makes it go away.

    Last time I got really pissed off and gave the pre-amp a mighty whack! It's been fine since...

  5. #5
    Wammer
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    Hmm, OK - looks like I wont' be removing the preamp ground then!

    Thanks for your replies. Aesthetically, I'd rather not shift the pre away from the power and yes, the isolator HAS solved the problem, so maybe the problem wasn't proximity to begin with. I haven't given it a proper A/B comparison yet, but it has completely removed any trace of buzz. However, there is now a mushy interference sound when you turn the volume up to max (nothing playing of course) that wasn't there before. I cannot hear it at normal gain levels though, so this may be incosequential. The Sowter transofrmer solutions look good. Does anyone acutally incoporate these into GLIs, or would this be a DIY job (err, no thanks!)?

    DT
    SACD: Marantz Pearl Lite
    Vinyl: Dynavector DV10x > Thorens TD309 > MF KW550 (JS Audio) > Wilson Benesch Square Two

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