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Old 9th January 2006, 09:11 PM   #1
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Default I know this is illegal but is it dangerous or cunning.

I wish all my posts did not seem melodramatic, but the non dangerous things I do by trial and error!

Ok I have a ground loop problem, some of my nice audio signal trickles through the ground!

After building my first mains filter one of the components gave me an idea. it has an 250v MOV. it has an extremely high resistance upto 250v then it conducts readily. Normally used across live/neutral as a surge protector.

I had an idea, if i get a 12v MOV and put it inline with my earth wire. anything that trickles down the earth below 12v is stopped (like a leaky audio signal) but when i do get a case short the 230v flies on through!

Is there anything I am overlooking?

while I am here can anyone explain what the hell a ground loop actually is, i have had some simple descriptions but nothing else!

thanks for reading
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Old 9th January 2006, 09:19 PM   #2
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Default Re: I know this is illegal but is it dangerous or cunning.

Quote:
Originally posted by Peter Scowcroft


I had an idea, if i get a 12v MOV and put it inline with my earth wire. anything that trickles down the earth below 12v is stopped (like a leaky audio signal) but when i do get a case short the 230v flies on through!

Is there anything I am overlooking?
Hi Peter

And if the MOV fail open , as usually they do ...
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Old 9th January 2006, 09:19 PM   #3
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Peter, please read this.
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Old 9th January 2006, 09:24 PM   #4
poobah is offline poobah  United States
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No No -

Grounds amust be solid connections or they serve little purpose.

Grounds are provide for 2 basic reasons; 1) to keep exposed metal/conductors from injurious potentials. 2) to provide a low resistance path for return currents so that circuit breakers or fuses will open.

The resistance of an "active" MOV is NOT so low... nor can it carry the return currents without exploding.

Why do you believe you Have a ground loop? Describe the symptoms and attack the cause. These problems are best solved by more traditional means.
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Old 9th January 2006, 09:27 PM   #5
SY is offline SY  United States
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And keep clear in your head the difference between safety ground (which you NEVER want to interrupt!) and signal ground, which can be lifted.
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Old 9th January 2006, 09:55 PM   #6
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Hi,

I was just curious about that. no worries I won't try.

Thanks for the link pinky. I have followed your advice from last time. I have bought a pre with XLR connections. That fixes it for the front two channels (where the buzz was BAD) the others are not to much of a prob. the buzz is quiet, and when I have my 5.1 on it is generally VERY noisy so I can;t hear it.

shame, I thought I had thought of something cunning.
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