Sunday, February 11, 2018

Using unshielded ethernet Cat5 Cat5e Cat6 wire as an XLR audio snake

This article will focus on un-shielded Ethernet cable to get THREE (3) analog audio channels vs the commonly advertised products providing four (4) channels on shielded Ethernet cable.
  • Cat5/6 Un-shielded Ethernet wire will allow 3 balanced "XLR" analog audio channels
  • Works with phantom power and works with ClearCom
  • Audio is clean, no buzzes, no hums, no distortion.  
  • Solid or stranded core (stranded less prone to breaking if coiled often)
  • 1000 foot XLR snake is possible.

What's the main differences between UN-SHIELDED and SHIELDED Ethernet cable for audio? 
  1. Shielded Ethernet has the same 4 pairs but with an additional wire allowing for 4 (four) channels.
  2. COST.  UN-shielded Ethernet is inexpensive cable found almost everywhere and is 2-4 times cheaper than its counterpart.
But we need the shield for audio quality right?

No. The shield (metal foil) found in some balanced mic cable only provides rejection enhancement for certain situations.  The way balanced audio provides clean signals over a wire results from the positive (in-phase) and negative (out-of-phase) balanced relationship of the analog signal as it travels together over the cable pairs.



UN-SHIELDED ETHERNET CABLE (two channels)
We can easily just connect an XLR pins on either end of the Ethernet wire and get 2 channels of audio.  XLR uses 3 wires for channel, and Ethernet has 8 wires, so that will easily get us 2 channels as shown in this diagram.

Solution A - Two balanced channels

XLR over Cat5 using standard wiring methodology (2 unused wires)

UN-SHIELDED ETHERNET CABLE (three channels)

The trick to maximize the number of audio channels on either Ethernet type cabling is sharing the ground connection with the other audio channels on the cable.

By using just 1 of the wires on the cable for the ground, and connecting it to the ground points for each channel, we free up an additional wire on the cable


The ground wires are both going to the same brown wire.  The Green wires are now unused.


Solution B - Three balanced channels by sharing the ground.

In this example each positive and negative wire is connected to orange, green or blue.  But now the ground points are on the same brown wire on either side of the Ethernet cable.  This is the trick to get the additional balanced audio channel!


Wiring Diagram

Here are some more detailed wiring diagrams.  In this example the brown/white stripe wire is used for common ground, the brown wire can either be ignored, or attached to the same points simultaneously as the brown/white wires.

Channel 1 blue pair 
Channel 2 Orange Pair 
Channel 3 Green Pair 
Ground Brown pair 


A variation is assigning one channel its own dedicated ground wire since we still have a brown wire going unused. Perhaps some channels are going to a different location, this might help to address that situation.  (Channel 1&2 goes to FOH, Channel 3 goes to a rented mobile production truck)

Implementation methods

Here are a few termination examples that could be used, but with an understanding of the wiring diagram, there are many possibilities that could be explored.

This example uses DB9 serial connectors.  





This example uses DB9 breakout boxes which don't require soldering.  (detailed implementation below)

Possible Applications
Send audio through preexisting Ethernet infrastructure allowing connections between locations (MUST bypass all Ethernet components like hubs or switches) allowing analog signals via the in house wires.  
Must not pass through any electronic equipment, direct patching between patch bay ports is ok.

In a situation that use this method all the Ethernet jacks were patched directly by IT staff.  Essentially a super long Ethernet wire cable, but not limited by the Ethernet length of 300 foot normal limitiation.  A 1000' or more long connection in many cases is achievable.

TOO LONG; DIDN'T READ

An efficient no soldering way to build pigtails using an RJ45 breakout box connected to the XLR connectors.  The one shown is a "female" adapter.
Use standard Ethernet cable with RJ45 ends to link each end of the snake.


In the diagram below, I show a possible wiring diagram that also takes into consideration the "split pair" wiring that a properly built RJ45 Ethernet cable needs to follow.
Connect the Positive, Negative and Ground wires from each XLR connector to the terminal adapter according to the diagram shown.
"Hey, why is channel 2 wires not seem to be in order in this picture?"
This means that the second pair although twisted together, needs to be connected to pins 3 & 6 at each end to ensure the positive and negative signals travel together and are not 'split'. (where the +/- signals travel on separate wires.  This will negatively impact the signal greatly if not followed!


Repeat the process for the other end.  NOTE how two of the XLR ground connections share the same connection point.  Sharing the ground allows for the 3rd connection and has no effect on the signal quality of either channel.

IMPORTANT!!!

A properly built RJ45 Ethernet cable uses pin groups of  
ORANGE PINS: 1 & 2
GREEN PINS: 3 & 6
BLUE PINS: 4 & 5
BROWN: PINS 7 & 8


So the seamingly 'all over the place' wiring in the above picture is required to be followed for this to work successfully.

If you connect the pigtails to a properly built ethernet cable, clean audio should now pass across the wire.  

16 comments:

  1. Replies
    1. It should. I've made them from Cat3, they were only 150' long, but i dont think there would be much difference.

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  2. I got here much interesting stuff. The post is great! Thanks for sharing it! Cat 6 Cable

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  3. I would think that there is almost no capacitance in this scheme, and therefore no high-frequency attenuation. Best to use stranded CAT5e cable meant to use in making patch cords. Comes in 1000' rolls.

    ReplyDelete
    Replies
    1. Good call, the stranded cable is less prone to failure due to a cable break, especially if you coil the cable up alot.

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  4. What about phantom power ??????

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    Replies
    1. Yes, works with Phantom power. Have had no personal issues with it.

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  5. Hi men greetings from.colombia;can i use utp cat 5e?

    ReplyDelete
  6. Hi! Thanks for this nice explanation! I see there are some examples of boxes that are able to connect 4 XLR (or DMX) channels to a Cat6 cable. In my understanding, they then use all the cable pairs for XLR channels, but what are they doing with ground?

    ReplyDelete
    Replies
    1. This article discusses this. Shielded cable = 4 connections, regular cable = 3 connections.

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  7. Thanks for this helpful post. How To Make Ethernet Cable and Crimp
    RJ45 Connector Without Crimping Tool, Fix Broken Ethernet

    Cable
    . You can learn how to crimp without a crimping tool or make ethernet cable without crimping tool

    for crimping rj45

    ReplyDelete