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Curious audio puzzle (TRS -> XLR)

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Rob Gow:
I have a curious audio problem, that only happens when I use my snake. This has to do with my subs, which are XLR fed.

When I'm not using my snake, everything is fine. I have TRS outputs on my Yorkville Unity processor. So I have a TRS to XLR adapter cable. No problems, everything is fine.

When I use my snake, it has a TRS male, at the fantail, and TRS female on the box (obviously) so I use the TRS to XLR at the box, and then XLR to the sub. Everything is fine, but it just won't reach to my rack from the fantail, so I use a TRS extender (male to female)

Everything checks out fine, until I use the extender.

The  TRS to XLR checks out fine:

Tip = pin 2
Ring = pin 3
sleeve = pin 1

With the TRS to XLR plugged into the box, it checks out fine as well, from fantail to the end of the adapter cord.


Tip = pin 2
Ring = pin 3
sleeve = pin 1

But when I add the TRS male to female extender to the fantail and check, this is what happens:

Tip = pin 2 & pin 3
Ring = dead on pin 2 & 3
sleeve = pin 1

If I test the extender on its own with a TRS to TRS patch cable, it's fine:

T = T
R = R
S = S

If I test the extender with the TRS -> XLR it checks out as well:

Tip = pin 2
Ring = pin 3
sleeve = pin 1

It's just the combination of all 3 that gives me the problem. My workaround is to not push the TRS to XLR in all the way, at the box. I know that's not right, but it works.

Any ideas?

Again, everything on their own checks out. With the snake, I plug a short TRS patch cable into the box, and testing from the fantail,

T = T, R = R, and S = S.

It has always done this from the start, with that combination. Of all 3 cords, has nothing to do with the sub or Unity processor, as the testing is just with the wiring alone. (final XLR cord from the TRS to XLR to the sub has no effect, so it's been left out of the testing chain)

Any ideas? Testing signal with a multimeter.

Geoff Doane:
Rob Gow wrote on Mon, 06 December 2010 11:50

Tip = pin 2 & pin 3
Ring = dead on pin 2 & 3
sleeve = pin 1

Maybe there's something funny with the different connectors and they don't mate quite the way they should.  With signal on both pins 2 and 3 at the sub, the CMRR of the input will cancel out any signal that is there.  Pulling the plug part way out unbalances the signal, but now the input XLR just sees one signal, and it works.

I know it doesn't answer the question, but my solution would be to change the TRS connections on the snake to XLR, and use an extra long TRS>XLR adapter at the rack to reach the snake return.


Alfredo Cannon:
If your snake is balanced cable (which it should be) just make sure your trs/xlr cable you plug into the box is also balanced cable. This is not your problem, though. Just making sure you know you should be using balanced instead of unbalanced.
 Now. What I would do is use xlr mic cable as extension cable. They connect to eachother to make one long cable. You can try that or just wait for a pro to answer your question. I'm an amateur sound guy.

Jeff Wheeler:
Get an extender that mates better with your other connectors?

Christian Tepfer:
In addition to what's already said, why do you use a TRS extender anyway? Since you do to XLR you could extend that with the better connector system.


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