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Author Topic: Mic over twisted pair  (Read 9765 times)

Aaron Bott

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Mic over twisted pair
« on: October 21, 2011, 11:30:40 pm »

I know it has been mentioned in other posts regarding line levels over cat5e, but is it possible to run mics over cat5e? The reason I ask is I run sound and lighting for a DJ with live percussion at school dances and my FOH booth is usually on the opposite end of the gym. Our cabling is normally run along rigged truss at distances of 75-150'. Generally I've been running line levels (DJ mixer, returns) via cat5e but now the percussionist is a regular thing and we run 4 mics for his kit. I was wondering if it's possible to run 2 mics per cat5e (pair 1- mic 1/3, pair 2- mic 2/4 pairs 3/4- pin 1 ground --respective to which cat5e cable) with 2 cat5e cables. I feel it would be easier to run 3 cat5e's than to lug along my 150' 24/4 snake. All cat5e is STP for what it's worth. Also, Our cams for power are run on a separate truss so there is no interference other than a L5-20 cable run for our sound board, laptop, and lighting board.

Thanks in advance!
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Aaron Bott
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Please excuse any typos, abbreviations, or brevity as I frequently utilize my iPad to access PSW.

Jonathan Johnson

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Re: Mic over twisted pair
« Reply #1 on: October 22, 2011, 12:33:14 am »

I know it has been mentioned in other posts regarding line levels over cat5e, but is it possible to run mics over cat5e? The reason I ask is I run sound and lighting for a DJ with live percussion at school dances and my FOH booth is usually on the opposite end of the gym. Our cabling is normally run along rigged truss at distances of 75-150'. Generally I've been running line levels (DJ mixer, returns) via cat5e but now the percussionist is a regular thing and we run 4 mics for his kit. I was wondering if it's possible to run 2 mics per cat5e (pair 1- mic 1/3, pair 2- mic 2/4 pairs 3/4- pin 1 ground --respective to which cat5e cable) with 2 cat5e cables. I feel it would be easier to run 3 cat5e's than to lug along my 150' 24/4 snake. All cat5e is STP for what it's worth. Also, Our cams for power are run on a separate truss so there is no interference other than a L5-20 cable run for our sound board, laptop, and lighting board.

Thanks in advance!

Well, it won't cost you much to try it out. If it sounds bad, don't do it.

I'm not so sure that you even need a ground (your pairs 3 & 4). The ground isn't carrying any signal; in a balanced cable all the ground does is provide a drain for the shield. Your UTP CAT-5e cable has no shield, so having a ground really isn't a benefit.

If you were concerned about noise, you could get shielded twisted pair (STP) CAT-5e and ground the shield. Sure, it costs more than UTP, but the shield provides protection from external EMF. You could experience crosstalk between the pairs, especially if you run a line level on one pair and mic level on another in the same jacket (whether you use STP or UTP).
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Stop confusing the issue with facts and logic!

Aaron Bott

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Re: Mic over twisted pair
« Reply #2 on: October 22, 2011, 12:50:17 am »

As mentioned, I do use only STP (even for my Ethernet runs) due to not knowing from gig to gig if the power will be run parallel to signals or not.
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Aaron Bott
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Jordan Wolf

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Re: Mic over twisted pair
« Reply #3 on: October 22, 2011, 02:51:38 am »

If your drummer palys hard enough and your mics are sensitive enough, you might just be running around +4dBu anyway - talk to the guys who use the last few channels on their 01V96 as drum channels...line level input and no problems.

That being said, if any mics require +48V, then you're out of luck since you need that ground reference.

If you're using dynamic mics, go for it.  It can never hurt to have a run of UTP/STP somewhere...you'll want it for something sometime in the future.

I would recommend making a breakout cable using Ethercon connectors so that yo ucan disconnect them from the permanently attached run and store them safely.  Go with whatever regualr XLRs you need on the other end.  Also, when you solder/crimp the connections inside the connector shells, keep the pairs twisted as close to the solder/crimp point as possible.  That will aid in the CMRR of that channel.
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Jordan Wolf
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Aaron Bott

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Re: Mic over twisted pair
« Reply #4 on: October 22, 2011, 03:56:03 am »

That being said, if any mics require +48V, then you're out of luck since you need that ground reference.
If I end up needing Phantom power for anything, I'm going to run an active preamp at the stage so no worries.

If you're using dynamic mics, go for it.  It can never hurt to have a run of UTP/STP somewhere...you'll want it for something sometime in the future.

I would recommend making a breakout cable using Ethercon connectors so that yo ucan disconnect them from the permanently attached run and store them safely.  Go with whatever regualr XLRs you need on the other end.
Just a refresher on this.. I do only portable PA with my equipment. This is a mobile system that runs for a DJ that does several schools in our area. We want to make this as modular as possible which is why I'm using Cat5e also. It will have pigtails to go to audio connectors and I can use the appropriate length of factory-terminated twisted pair.
Also, when you solder/crimp the connections inside the connector shells, keep the pairs twisted as close to the solder/crimp point as possible.  That will aid in the CMRR of that channel.
No worries. I own two companies (1 for production services, 1 dealing with structured wiring). The ends will be terminated using a 110-type punchdown tool from Fluke Electronics. I'll be punching down the XLR pigtails to the RJ45 jack and running Cat5e cables between the jacks.

Thanks for the reminder though. I'm sure others here on the forum will benefit from knowing that if they weren't already familiar with it.
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Aaron Bott
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Please excuse any typos, abbreviations, or brevity as I frequently utilize my iPad to access PSW.

Aaron Bott

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Re: Mic over twisted pair
« Reply #5 on: October 22, 2011, 03:58:29 am »

Also, another question to add to my original post...

Where would you all suggest getting stage boxes to use for breakout panels? I want something about 16 gauge steel boxes. I would like them to be the same or similar to the boxes used for stringers or snake heads. I just want to mount 4-8 XLR connectors on the top plate and have 2-3 RJ45's come out the side that I can patch to. I have a fabricating shop I will have cut the inserts if needed but I would like to buy the actual part to have them start out with.
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Aaron Bott
Untouchable Productions

Please excuse any typos, abbreviations, or brevity as I frequently utilize my iPad to access PSW.

Dave Scarlett

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Re: Mic over twisted pair
« Reply #6 on: October 22, 2011, 07:29:57 am »

Also, another question to add to my original post...

Where would you all suggest getting stage boxes to use for breakout panels? I want something about 16 gauge steel boxes. I would like them to be the same or similar to the boxes used for stringers or snake heads. I just want to mount 4-8 XLR connectors on the top plate and have 2-3 RJ45's come out the side that I can patch to. I have a fabricating shop I will have cut the inserts if needed but I would like to buy the actual part to have them start out with.


Have a look at Penn Elcom
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Aaron Bott

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Re: Mic over twisted pair
« Reply #7 on: October 22, 2011, 01:46:17 pm »


Have a look at Penn Elcom
Thanks for the link but I didn't see anything to fit my needs.  I guess I just want the best recommendation for a box to utilize for the end. I'll be using D-size Neutrik connectors on the panel.
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Aaron Bott
Untouchable Productions

Please excuse any typos, abbreviations, or brevity as I frequently utilize my iPad to access PSW.

Rob Spence

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Re: Mic over twisted pair
« Reply #8 on: October 22, 2011, 02:43:19 pm »

Whirlwind will sell the parts.

Why not just get a 150' 6 pair drive snake and be done with it?
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Aaron Bott

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Re: Mic over twisted pair
« Reply #9 on: October 22, 2011, 03:58:06 pm »

Well if I use a modular connection (RJ45), I can add and decrease length as needed rather than having a cable trunk filled with half the snake or having a huge figure 8 on the floor.
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Aaron Bott
Untouchable Productions

Please excuse any typos, abbreviations, or brevity as I frequently utilize my iPad to access PSW.

ProSoundWeb Community

Re: Mic over twisted pair
« Reply #9 on: October 22, 2011, 03:58:06 pm »


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