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Author Topic: One wire input stage box  (Read 2896 times)

Debbie Dunkley

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One wire input stage box
« on: January 17, 2013, 01:23:13 PM »

I thought I would do a quick test of each channel on my 100 ft snake with a multimeter. Ironically, I found input # 4 pin 3 works but  pin 1 is not working. BUT when I connect a signal source (mic) in, it does in fact work. Does this mean it is working unbalanced as opposed to balanced???
Just wondering.........and if so, will this cause some noise?
« Last Edit: January 17, 2013, 03:16:16 PM by Debbie Dunkley »
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Geoff Doane

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Re: One wire input stage box
« Reply #1 on: January 17, 2013, 03:52:41 PM »

Pin 1 is the shield, which doesn't carry signal in a balanced line.  Since we almost always are running balanced audio in a 100 ft. snake (we always should be), the channel will appear to work.

What it won't do is work for a phantom powered mic, since the shield is used for the DC power return.  Depending on how noisy your environment is, you may also notice more noise in that channel, particularly RF or neon signs.

GTD
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Debbie Dunkley

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Re: One wire input stage box
« Reply #2 on: January 17, 2013, 04:01:04 PM »

Pin 1 is the shield, which doesn't carry signal in a balanced line.  Since we almost always are running balanced audio in a 100 ft. snake (we always should be), the channel will appear to work.

What it won't do is work for a phantom powered mic, since the shield is used for the DC power return.  Depending on how noisy your environment is, you may also notice more noise in that channel, particularly RF or neon signs.

GTD
Thanks for the response ..... I have checked the connection points both ends so I can only assume there is a break in the cable which of course I will not be fixing at this point. So going forward, I will not be able to use phantom on this channel and there may be some extra noise. But it is safe to continue using ...correct??? Who knows how long it has been this way and so far, no issues....
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Geoff Doane

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Re: One wire input stage box
« Reply #3 on: January 17, 2013, 08:13:05 PM »

But it is safe to continue using ...correct??? Who knows how long it has been this way and so far, no issues....

I can't think of a situation where it would be unsafe (like give you a shock), but you need to be aware of its limitations.  If you could swap that pair with a return line, you might be better off.  The chance of picking up noise is almost non-existent at line level, and you won't be running phantom power on it either (although you won't be able to use it for Clear-Com, which does require all three wires).

If swapping with a return isn't practical, I might be tempted to jumper the shield from Ch. 3 over to the chassis XLR for Ch. 4, just so phantom would work, and you would have some shielding in a noisy environment.  Does anyone else want to offer an opinion on the downsides of doing that?  I know it's not usually done, but if there is no other shield connection anyway...

GTD
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Debbie Dunkley

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Re: One wire input stage box
« Reply #4 on: January 17, 2013, 09:00:14 PM »

I can't think of a situation where it would be unsafe (like give you a shock), but you need to be aware of its limitations.  If you could swap that pair with a return line, you might be better off.  The chance of picking up noise is almost non-existent at line level, and you won't be running phantom power on it either (although you won't be able to use it for Clear-Com, which does require all three wires).

If swapping with a return isn't practical, I might be tempted to jumper the shield from Ch. 3 over to the chassis XLR for Ch. 4, just so phantom would work, and you would have some shielding in a noisy environment.  Does anyone else want to offer an opinion on the downsides of doing that?  I know it's not usually done, but if there is no other shield connection anyway...

GTD

Good ideas Geoff.. The jumper wire will be easier to accomplish and will keep the color coding correct. It is a Peavey box which uses push in connectors so I will need to get wire to fit into the existing slot of the connector as there is no opening access into the XLR chassis mount connector.  I am pleased there is no shock hazard which was my main concern although like I said, I have probably been using it this way for a while and it hasn't been a problem so far. Thanks again for the info....
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A young child says to his mother, "Mom, when I grow up I'm going to be a musician." She replies, "Well honey, you know you can't do both."

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Re: One wire input stage box
« Reply #4 on: January 17, 2013, 09:00:14 PM »


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