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What part of the cable shall I CUT????

Discussion in 'Home Cinema Speakers' started by WBC, Jan 4, 2003.

  1. WBC

    WBC
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    Guys,

    I have an earthing loop problem and it was suggested to cut the outer sheathing of the cable going to the sub.

    The cable is an IXOS (Gamma ??) and I have undone the connector to find it doesn't seem to have an outer sheilding like a normal coax cable.

    It seems to have two cables. A red, which looks like it goes up to the main point of the connector and a clear, that is soldered to the side of the connector.

    Can anyone confirm which one I need to cut???? I can't afford to get it wrong as the cable runs in a channel cut out of a concrete floor and has been covered with wooden flooring.

    Thanks in advance & Happy New Year !! :D !!

    Stace
     
  2. buns

    buns
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    Firstly im confused....... its been suggested that cutting a bit of the outer sheathing?

    Im half assuming what is intended is that you directly earth the sub cable...... but id need a bit more info before i could tell you what to cut!

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  3. cybersoga

    cybersoga
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    Does your cable look like this?
    [​IMG]
    If it does, it's not a gamma it's a cheaper 1081.

    The Gamma cable looks like this:-

    [​IMG]

    I wouldn't cut the cable if I were you, does your sub have an earth isolation switch? What sub is it?
     
  4. WBC

    WBC
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    Thanks Guys for the quick response.

    Yep its definately the IXOS Gamma. What I mean't to say in the original post was someone (on another thread) suggested;

    " Disconnect the outer shield of the phono lead at one end only (usually the sub end - but IMO this is just convention, I don't think it really matters which end)
    This is probably the easiest and most effective solution - it may increase the cables susceptibility to EMI/RF a touch, but that shouldn't be an issue in practice. "

    As you can see from the Gamma picture, its not quite as straight forward as one would like!!!


    My subwoofer is a Yamaha YST-SW305. It is connected to the amp via the phono cable and sits about 12ft away from the amp. It plugs into a different plug socket to the rest of my kit (if thats relevant?)

    Any suggestions on fixing this problem is appreciated.

    Thanks Again
    Stace :D
     
  5. cybersoga

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    It's the clear wire soldered to the outer part of the plug that is the sheild, but i'd get a a second opinion first! Does the sub stop humming when this cable is unplugged from the sub? Do you have any other cables plugged into the sub?
     
  6. buns

    buns
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    The shielding should only be connected at one end, if it was connected at both, it wouldnt work right! You would definitely get some sort of loop going on!

    The suggestion made might well work, im not really that sure.....

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  7. WBC

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    Guys,

    There are no other cables plugged into the sub.

    The sub stops buzzing when the amp is turned on or when the phono cable is disconnected.

    Thanks
    Stace
     
  8. buns

    buns
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    Ah..... what amp is it? It definitely sounds like something up with it. Almost sounds although the power being turned of stops it being earthed in some way.

    The clear cable definitely sounds like it is the one in question. But I dont know how much good youd do by disconnecting the shield.

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  9. WBC

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    The amp is a Sony STR-DB925.

    Stace
     
  10. buns

    buns
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    Have you found any other owners of that amp with or without a similar problem?

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  11. WBC

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    Can't say I've asked the question but I haven't found anything when I've done some detailed searches!!!

    Stace
     
  12. buns

    buns
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    It just sounds to me like the problem is a function of the amp..... if the amp isnt connected, you dont have a problem. When it is connected you do....... so i have to look suspiciously at it!

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  13. WBC

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    I have just checked out both ends of the phono cable and the shielding is definately connected to the outer side of the phono connector at both ends!!

    When I said "the sub stops buzzing when the amp is turned on", I meant when the amp is turned on from standby. Surely if it was the amp it would buzz in both standby and 'ON'

    VERY:confused:
    Stace
     
  14. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    It's not a shield it's the earth signal that is connected at both ends. Disoconnecting it at either is likely to result in no sound at all....which will cure the buzz.

    Is this buzz a constant volume. Does it change in charcteristic if you move other cables. Is the VCR/SKYBOX etc connected to your amp and if so what happens if you diconnect the INCOMING tv aerial signal to these components?


    Gordon
     
  15. Bone Daddy

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    Have had friends have problems with the earthing loop problem on subs before and the easy way was to see if the sub mains plug was wired to the earth pin as well, if so just disconect it leaving the blue and brown connected and taking care to make sure that the earth is away from those connectors,your system will be earthed somewhere along the line,this will be why you have the looping problem.they all said this cured the buzzing and apparently all are alive and well today ;)
    Please feel free to say if you think this is a bad idea and could cause problems for Stace,just adding what I did once on an old Rel that had the same problem,and as mentioned friends have cured it this way with no problems at all.
    Hope this is of use.....
     
  16. WBC

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    Good evening Gents, Thanks for the added input!!!!

    Just so you guys are aware;

    I have my Sky Digibox connected to my amp via the phono outputs. My DVD is connected to the amp via a digital coax. I have an FM aerial connection to my amp. Apart from that, nothing else is connected (not interested in VCR connected to amp, old technology with a bad picture ;) , only any good for catching up on eastenders!!!!)

    I do not have a tv aerial connected anywhere on this system, I purely use sky connected to the TV via scart and phono to the amp as mentioned above. (I tend to watch & listen to all tv broadcasts straight from the TV. It gives more impact to DVD's when using the amp!! :D !!)

    When the sub buzz's, it is a constant buzz in both pitch and sound levels (it doesn't seem to fluctuate, However the buzz will get louder if the sub volume is increased).

    As soon as the amp is switched from standby to ON, the buzzing stops.

    The buzzing will also stop if you disconnect the phono cable (whilst the sub is turned on!!).

    This is driving me crazy.

    All and any help is VERY much appreciated
    Stace
     
  17. 337GUS

    337GUS
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    Hi

    Agree with Bone Daddy.

    Had this with a Kenwood amp and Rel sub a few years ago, removing the earth in the mains plug fixed it.

    Gus
     
  18. WBC

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    I thought I had heard that removing the earth from the sub was dangerous?????

    Isn't that the case???? I don't really want my bo****ks splattered over the wall next time I turn the sub on. No ones that kinky????

    Stace :D
     
  19. The Sheriff

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    hi, i had the same earth loop with my equpment. i have the gamma cable aswell. Have tried it with other cables and its fine so i was sure it was the cable, then tried it at a mates house and it worked fine, really puzzled me.

    in the end what i did was connect an exposed piece of metal on the sub to the earth pin and plugged it into the mains (via the one pin). this seemed to stop the problem when i had my amp on, but hummed when i switched it off?

    BTW, the equipment i am using is: paradigm servo-15 sub, sont 940 receiver and the gamma cable
     
  20. WBC

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    Mr Cash,

    Thanks for the response but, what does this mean????

    " in the end what i did was connect an exposed piece of metal on the sub to the earth pin and plugged it into the mains (via the one pin). this seemed to stop the problem when i had my amp on, but hummed when i switched it off? "

    I'm getting confused, your basically saying your sub did the opposite to mine. I'd like to say that was a fix but my amp is off more than it is on and I am pretty sure my wife would throw me out if there was a near constant buzz in our living room ;) !!!!

    Stace :D
     
  21. RobertP

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    For the sake of a quick test why not use a short piece of ordinary wire... wrap one end around the phono plug centre pin and poke the other end into the subs phono socket. Now you will know what effect cutting the outer shield connection would have without actually butchering your cable.
    If there is no alternative route for the earth from amp to sub you will prob. get no sound.
    Personally I've never had an earthing problem. The first thing I'd check is that you really do have a good earth bond to your mains power socket outlets!
     
  22. WBC

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    Guys

    Thanks for all your responses but I still haven't got a fix.

    Any more help would be appreciated!!!!

    Thanks Again
    Stace
     
  23. cybersoga

    cybersoga
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    If it's any help, my sub doesn't hum and i'm using an ixos gamma sub cable. Stace - what happens if you unplug everything from the amp except the speakers, sub and power? I am wondering if the earth problem might be caused by something else plugged into the amp.
     
  24. WBC

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    I'll check that out tonite!

    Any other opinions and recommendations appreciated :D

    Stace
     

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