Long XLR run

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Eric Lenasbunt

Sophomore
Feb 10, 2013
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I have an event at a lake that needs some fills around different parts of the park. Looking at running a pair of QSC K12 in the main area and then another pair about 1000' away.

I was either going to link out of the first pair or run the second pair off of an aux. Anything I should be concerned about or considering in such a long cable run?

I have run wirelessly from speaker out to in on an event like this before, but this park has far more trees, so thinking it's a better idea to run wired.

Thanks!
 
Re: Long XLR run

Primary concern would be to have some form of 1:1 line-level transformer isolation with a lifted audio ground. I'll usually put these at the remote speaker so that the longest cable's shield has the benefit of the source's ground connection.
 
Re: Long XLR run

Milt Hathaway said:
Primary concern would be to have some form of 1:1 line-level transformer isolation with a lifted audio ground. I'll usually put these at the remote speaker so that the longest cable's shield has the benefit of the source's ground connection.
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Yep. You may want to run the remote pair off an aux so that if there is an issue - cable short, whatever, you don't nuke the local pair, too. 1000' isn't a problem to drive with a line-level source, but as Milt said, you want to lift the ground at the remote end, ideally with an isolation transformer.

A couple of these will do nicely:
http://www.audiopile.net/products/Electronics/MST-103_mic_splitter/MST-103_cutsheet.shtml

or for a more known brand name: http://whirlwindusa.com/catalog/bla...s/iso-2-dual-line-level-isolator-and-balancer

or: http://www.radialeng.com/jisoproiso.php
 
Re: Long XLR run

If you check the specs on that Audiopile unit I think you will find it is intended for mic levels not line level signals. The Whirlwind would be a better choice.
 
Re: Long XLR run

I think the ones we have around are whirlwind or Proco if I remember correctly. Audiopile is too far from me, I wouldn't see that shipment nearly soon enough
 
Re: Long XLR run

Until you get to around 4000' feet or you don't need to worry about anything.

The idea of a iso transformer is a good one-just MAKE SURE it is line level or it will saturate and distort.

Horizon makes the isoline-2 that works well.

And most of the "hum eliminators" will work-as they are usually line level and 1:1 winding. A direct box is not 1:1 winding.

The isolation of a transformer is also a good idea since it provides physical isolation between different sources-especially those that may be on different AC supplies.
 
Re: Long XLR run

Chuck Simon said:
If you check the specs on that Audiopile unit I think you will find it is intended for mic levels not line level signals. The Whirlwind would be a better choice.
Click to expand...

The EWI lists <1% distortion at +8dBv. The Whirlwind doesn't list a spec for distortion, but lists a max input of +28dBm. I have used the EWI box in exactly this situation with line-level sources and no issues (in an admittedly low-demand situation), and they're $33. YMMV and more is usually better, but $33 in the rain may be a better choice than $100 in the rain.
 
Re: Long XLR run

The best line driver in the whole damn world is a dbx 160. Stupidly low output impedance (20 ohms or so) and will drive a 200 ohm load at +22 all day long.
 
Re: Long XLR run

Lee Douglas said:
Is this presuming that the aux output is balanced or would this not make a difference in this application?
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If you are directly driving a long line, you definitely want at least an impedance-balanced output driving a full balanced input to get the common-mode noise cancellation. You could theoretically use the iso transformer to balance an unbalanced signal, but then the iso transformer needs to be at the source end of the run, and not at the remote end, so you lose out on some of the benefit of the grounded shielding, as Milt mentioned.

The good news is I can't think of a mixer released in the last 10+ years that has unbalanced auxes - even the cheapies are at least impedance balanced.
 
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