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Author Topic: Wired IEM Siamese Cable  (Read 2349 times)

Peter Kowalczyk

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Wired IEM Siamese Cable
« on: August 10, 2017, 07:37:59 PM »

Another 'custom cable' question!

My band is on wired in-ear monitors, and we're working on improving our cabling system.  I'd like to build a few custom hybrid cables that combine a 1/4" T/S instrument cable with a stereo Headphone extension cable.  Our Headphone amps are Behriner P1 and live on our pedalboards.  At the moment we loom an instrument cable with an off-the shelf headphone extension, but while it's been functionally okay (notwithstanding one player's defective headphone extension), it's a bit messy.  The one off-the-shelf guitar+headphone cable I found in an earlier search got bad reviews for reliability...

My question is what raw cable stock to use.  I initially figured standard star quad mic cable would do, but am now concerned that cross-talk between the headphone signal and the high-Z unbalanced instrument signal would be problematic.  So, now looking at two-pair cables with separate shields, such as this Gepco 6600:

http://www.gepco.com/products/proav_cable/analog_audio/singdual_2prshielded_M.htm?v=1

I assume that wiring both conductors of one pair to the tip of the T/S instrument line will be functionally equivalent to a standard unbalanced coaxial instrument cable; is this a fair assumption for a ~15' run?  One member plays sax with a bell mic, so I could use this same cable for him, with one pair as a plain ol' mic cable and the other as his headphone return.

Is there some other bulk cable stock you'd recommend for this purpose?  Any 'gotchas' I may be overlooking? 

Thanks as always!
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Frank Koenig

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Re: Wired IEM Siamese Cable
« Reply #1 on: August 10, 2017, 10:18:14 PM »

My question is what raw cable stock to use.

Hi Peter,

I think you are correct in assuming that mixing a mV-level, high-impedance instrument signal with headphone audio in "star-quad" is asking for trouble. I should think that individually shielded twisted pair should do fine, but I'd test it first before buying a 1000 ft. roll :) Maybe someone who has actually tried this will chime in. When running unbalanced signals in twisted pair, ground one member of the pair rather than tying both members together. This should give slightly better magnetic shielding. Electrostatic shielding is provided by the shield.

Twin, individually shielded pair (2-channel snake?) could be pretty useful stuff to have around in any case. I'm thinking stereo patch cords, etc.

--Frank
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Brian Bolly

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Re: Wired IEM Siamese Cable
« Reply #2 on: August 11, 2017, 08:44:02 AM »

For 2-pair, Belden 1509C should get the job done.
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Philip Roberts

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Re: Wired IEM Siamese Cable
« Reply #3 on: August 11, 2017, 02:03:18 PM »

http://www.gepco.com/products/proav_cable/analog_audio/singdual_2prshielded_M.htm?v=1

While I haven't used it for instruments/unbalanced use I'd consider Belden 1902, it's exceptionally flexible and has 2 individually shielded and jackets pairs.

Other composite cables like Belden 1347A that have coax and twisted pair might work well also but I think that 1902 will stand up to stage use better.

Philip
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Peter Kowalczyk

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Re: Wired IEM Siamese Cable
« Reply #4 on: August 11, 2017, 06:47:28 PM »

Thanks all,

Just ordered 60' of Belden 1902A to make 4 15' runs (budget isn't ther for a whole spool at this point, Frank).  Braided shield and more / smaller stranding for better flexibility than the 1509C.  I'll let you know how it goes!!

Cheers,

Peter

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Re: Wired IEM Siamese Cable
« Reply #4 on: August 11, 2017, 06:47:28 PM »


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