EtherCON to Quad XLR Audio Snake

Need to conveniently transport 4 channels of balanced audio (or DMX, etc) across arbitrary varying distances? Do you have too many cables on your stage, or have a building that already has CAT5e+ wiring in the walls?

Enter the etherCON (Neutrik RJ45 connector) to XLR adapter. Several commercial variants of this idea exist, ranging from $60/pair to several hundreds of dollars per pair, but if you're a DIY-type that needs inexpensive audio snakes, this is a handy thing.

My use case is to simplify the setup and cable runs for the musicians in my band; each musician uses multiple channels of audio (mic + instrument), and so I can simply run "ethernet cable" of whatever length is needed to individual musicians' positions. The audio can be in either direction, so you could for example have 3 channels of microphone/instrument and one channel to return a monitor mix! This maps well to alternating between rehearsals and gigging, as we can leave CAT5e+ cabling in place in our rehearsal space and bring different cables with us to gigs, saving from rerunning cables every time we return to our studio. Each musician is responsible for his/her own end of the snake and their local cabling to their instrument(s), and the other ends of the snakes remain plugged into our (portable) digital mixer. Instead of plugging 16 cables in, we only have to plug in 4! (Combine this with rack ears that have D style holes, and you have a very slick rack-mount solution indeed!)

If you have a building with CAT5e+ installed in the walls that is not connected to ethernet switches/hubs/etc, then you can also run audio over your in-wall wiring! Neat.

Here's the schematic diagram from a commercial product that describes one possible implementation, also available as a screenshot above:

http://soundtools.com/pdfs/etherCONwiringdiagram.pdf

Caveat: all XLR ports on a snake will use a common ground, and that ground is connected to the shielding of the CAT5e+ cable. Not all cabling will have this shield: so if you wish to use phantom power with microphones (which will require this ground path), you will have to use shielded cable (which effectively has a 9th wire), connected to RJ45 connectors with an outer shielded connector. UTP cable (Unshielded Twisted Pair) will not work in this case. If you do not need phantom power for your mics, then you do not have to use shielded cable! (though in some cases it may help in noise rejection...)

Neutrik NE8FF etherCON female-female connector (~$18 at the time of this writing)

Neutrik DBA-BL (pack of 4) blank plate for D holes (~$9)

Monoprice 8764 3ft 4-channel XLR male to XLR female snake cable (~$10)

You can build the XLR ends yourself and not cut a short snake in half, but in my case I was building a number of these cables (in groups of 4) and it saved me considerable time and money. I simply couldn't beat a 4 channel snake for $10 - I only get paid in beers when I play music!

Soldering station (I used one set to 450 degF with 60/40 lead solder)

Wire cutters & wire strippers

Small blade (to cut the outer sheath)

Philips screwdriver (to [dis]assemble the shell)

Sharpie/marker (to mark the PCB to indicate polarity)

Drill or other method to make an even ~3/8" hole in plastic

Small vise (recommended - to hold the parts you're working on)

Multimeter (recommended - to test the cable as you build it)

Zip ties (recommended - to relieve stress from the solder joints)

Carefully cut the outer sheath of the snake (I used a small blade). Bending the snake and gently pressing a blade into the outer insulation will make cutting it easy.

Pull the outer cable insulation back so that about 2" of the 4 inner cables are exposed.

Carefully remove about .5" of insulation from each inner cable with the wire strippers.

Carefully remove .25" or less of insulation from each conductor, twist the ends, and tin with solder.

As the NE8FF connector comes with only one shell, you must decide which snake end will receive the shell. In my case, I wanted to attach the male-ended XLR connectors to my mixer rack (mounting the etherCON connector directly to the mixer rack), and I wanted the female-ended XLR connectors to be on stage and utilize the shells to protect the fragile soldered connections. You could purchase additional shells and blanking plates to protect both ends for the ultimate in portable solutions - in fact, I'd recommend installing blank plates on both ends of the cable just in case you decide to add a shell later, because it's not very easy to add after you've made your solder joints!

Drill a pilot hole, followed by a 3/8" hole in the center of the blanking plate. I used a drill press, holding the plate in a mechanic's vise, backed by scrap wood, but you can use anything so long as you are careful not to damage your fingers! Use eye protection so that you can continue to make DIY projects...

I used a hand reamer to enlarge the hole just enough to slip the cable through while still remaining tight.

Slide the blanking plate over the cable so that it is facing the direction you want it to end up in (flat side facing the snipped cable ends, convex side with graphic facing the XLR connectors).

Disassemble the connector shell, being sure not to lose any screws.

Cut the cables in half.

The stranded wire used in the Monoprice snake is unfortunately too thick for the through-holes in the etherCON PCBs, so rather than removing the wires completely, we'll leave them in place and simply solder onto them.

Mark the PCBs to indicate which wires are black. You can see I put a black dot on the edge of the PCB with a sharpie.

Trim the pairs of wires to about .25", pull off the insulation, twist, and tin with solder.

I recommend leaving the ground wire on the longer side, as that connection is a bit trickier to reach.

I did notice that the solder connections from the wires to the through-holes on the PCB were not very good (mostly just soldered on the back side), so I touched them up for robustness.

Begin soldering the wires from the snake ends to the PCBs. The mapping of colors and which side of the balanced pair connect to each pin is up to you, but you must at least be consistent on both sides, and if you are building multiple adapters and wish for them to all work together, they should all be the same, or you may end up very confused when you try to use them! Note that different commercial adapters have different pinouts, and so you may not wish to mix and match your adapter with others that exist in the world!

In my case, I always connected the wires with clear insulation to where I had put black dots. I also went in an order that followed the order of the conductors in the first snake I made; starting at the "NE8FF" silk screened label with red, I went clockwise red-yellow-white-blue.

Carefully solder the stranded shielded together, and join that with the single ground wire on the PCB.

After I made one end of the snake, I connected it to the second etherCON connector before I began assembling the second half. This allowed me to use a multimeter as I added each connection to verify that the pins were connected as expected (for each pair, checking female XLR pin 2 to male XLR pin 2 and female XLR pin 3 to male XLR pin 3).

Trim the ends of the wires to ensure that there will be no electrical shorts.

It's also a good idea to zip tie the connections that will not be protected by a shell.

Carefully work the outer insulation of the snake back towards the etherCON connector, so that it will fit within the connector shell.

Screw one half of the shell into place at both ends.

Add a zip tie around the cable next to the blanking plate on the inside, so that if the cable is pulled, it will not add too much strain to the solder joints. Note that this does not prevent it from excessive twisting, so do be gentle with your cables!

Screw the other side of the shell into place.

Now, what to do with the other end that does not have a shell to protect the solder joints? In my case, I want it to be permanently installed in a rack with my mixer. There are plenty of 1U tall rack panels available with a number of D holes in them, so you should be able to mount the etherCON connector in one of those positions. In my case, I am hoping to buy or build rack ears for my Behringer XR18 that have D holes integrated in them, so that I do not have to take up any additional rack space to mount my cables!

In my case, some of the audio runs in different directions within the same snake. After verifying that the connections are good, it's time for me to customize the ends of the snake to meet my specific needs.

Example: 3 channels of audio being sent in one direction, and 1 in the other direction. I remove two matching connectors and swap them. I still find it easier to begin with an off-the-shelf snake and then make this modification myself. Note that this adapter then becomes difficult to mix-and-match with my other adapters! It's still cleaner and cheaper than using two gender changers, though.

Example: I have a drum kit with microphones on all 7 shells mounted to a drum rack (7 + 1 extra on snare = 8 mics). Instead of starting with a 3' snake, I could start with a 10'+ snake, and permanently attach the snack to the drum rack, with custom wire lengths to match the position of each drum. The drum rack has a convenient quick audio connection of 2 CAT5e+ cables.