DIY Cat-5 Snake

[nickreich]

Hi All,

 

Finally got around to an idea I had a while back when I bought some Neutrik NE8FF Ethercon joiners. I often use Cat-5 (or 6) cable for very long balanced line-level runs. It's great for sending four channels of audio to video villiages, commentary booths, remote IFB transmitter racks or whatever. Commercially, this is available from ETS as the "InstaSnake" range, but considering there are no transformers (baluns) or anything involved, I've always thought they were a bit big. Here's my version.

 

To make a set, I used:

1x Neutrik NE8FF joiner. This has one Ethercon connector at each end, joined by what looks suspiciously like speaker wire. I remove one of the Ethercon connectors (to use on the other adapter), and de-solder the joining wires carefully from both ends. The Ethercon connectors used in this adapter have a custom PCB on the back, and a custom outer cowling that aren't available as a stock part on their own. The 2-part shell that makes up the adapter becomes the body for one of the two ends.

 

1x Neutrik NA-Housing kit - a slightly longer version of the 2-part shell from the adapter - for the other end of the Cat-5 snake. The second Ethercon from the NE8FF gets screwed on this.

 

2x Nylon Cable Glands of the size that fits an M12 hole (I'm sure there's a similar size Imperial version). These JUST fit 4 pieces of Canare L-2B2AT thin balanced cable through.

 

2x Neutrik NBB75DFI or similar BNC connectors in D-series panel-mount bodies. I remove the actual BNC connector - I only want the D-Series body for this project. The Cable Glands screw into these - the existing hole where the BNC went is perfect, and half the gland is hidden inside the D-series body's recess.

 

8x XLR-3s as required.

 

Start by removing the screws from both ends of the NE8FF adapter. Cut the joining wires half way between the two Ethercon connectors. Before removing the wire stubs, mark the side of the PCBs with a black sharpie next to the wire in each pair with a black stripe - it makes keeping your adapters in-phase easier! De-solder the remains of the joining wires, EXCEPT the one linking the grounds. This is a bit tricky, as they are plated-through PCB holes. Use a very small soldering tip and  de-soldering braid, or better, a proper de-soldering station.

 

Prep the Ethercon ends of the balanced hookup cable, but don't tin them as they'll never fit the little holes in the PCB. Push them through (I had to snip off 2 strands of the Canare one to fit) and solder in place. Twist all the shield drain wires together, solder close to the outer jacket of the cables, then use the remaining bit of original ground cable to join them to the Ethercon. Pop a little cable tie around the four cables near where they are stripped back. Screw the Ethercon onto one half of the housing shell.

 

Screw the Cable Gland into the D-series bodies from the panel-mount BNCs, then push the four bits of cable through, and slide the whole thing up to the other side of the housing shell and screw it on, and tighten the cable gland around the four cables. Then just put the other half of the housing shell on, and solder four XLRs to the other end of the fan-out as usual.

 

Repeat the whole thing for the other end, join with a short Cat-5 cable, then use a cable tester to figure out which XLRs are joined to which - and number them.

 

If you use normal unshielded (UTP) cat-5, then the four pairs will be 'floating' - the Pin 1 grounds will not be tied from end to end. This is not a big deal with line-level, as the pairs are optimally twisted. Many people even use it for mic level signals. If you want the snake to pass Phantom Power, or you need a ground connection for another reason (Comms, 'wet' IFB, etc), or are in a nasty EMF environment and want a shield - using overall-shielded Cat-5 or Cat-6 (S/UTP or STP) will allow this. You can use cable with normal RJ-45s or those fitted with Ethercon shells.

 

Cheers,

nick

[Steve Foy]

Nice work Nick.

[soundtrane]

excellent... 

 

next time you need just those shells, go check out aliexpress.com - lots of them in various sizes and shapes... 

 

-vin

[Toy Robot]

Awesome. Great work.

[TDP]

Awesome! Was just looking at the ETS stuff last week. Curious where you sourced the "nylon cable glands" from. Nothing coming up trying to find a grommet that fits a D series hole… 

[nickreich]

Hi Nirvana5253,

The grommet to fit a D series hole is two pieces, as described in my original post. The outer metal D series bit is the body part from a Neutrik D-series BNC-BNC through connector, a standard part of theirs. If you unscrew the BNC part (still useful as a BNC barrel), the metal body has a hole in it about 13mm in diameter, but with a flat on one side to stop the BNC rotating. The actual cable gland / grommet part should be available at any electrical supplies wholesaler. 

The one that fits the hole is sold as a 12mm size (they are sized for the thread on the back) - I'm sure there's a similar imperial size.

As you can see from the pictures, half of the Gland body is hidden inside the recess of the neutrik metal casting.

If the Neutrik BNC-BNC connector is hard to find / too expensive, Neutrik and others do make plastic blanking plates the same size as a D series connector, with the two screw holes moulded in. You could drill one of these out to suit tour chosen gland or grommet.

[Kenson]

Hi, May i know how this connection can deal with phantom power?

Is it we share the four ground connect and use the Cat5e shield as ground connection?

thanks.

[Malcolm Davies Amps CAS]

On 11/04/2014 at 8:50 PM, Nirvana5253 said:

Awesome! Was just looking at the ETS stuff last week. Curious where you sourced the "nylon cable glands" from. Nothing coming up trying to find a grommet that fits a D series hole… 

The D size hole is a slightly loose 24mm. you will find 25mm glands and grommets at any electrician supplier. There is nothing in the electrical game between 20 and 25mm as these sizes correspond with Imperial 3/4 and 1 inch. Hope this helps.

On 11/04/2014 at 8:50 PM, Nirvana5253 said:

Awesome! Was just looking at the ETS stuff last week. Curious where you sourced the "nylon cable glands" from. Nothing coming up trying to find a grommet that fits a D series hole… 

 

[nickreich]

Kenson - yes, the ground path is the shield of the STP cat-5e or better (you need to use the proper shielded RJ45s of course - which themselves connect to the Ethercon shells if you use them). The nice thing is that if you are just running line level, you can use normal UTP cat-5e cable - still get four floating pairs. Unless you are running through a power substation you'll be fine with the twisted pairs at line level.

Malcolm - sure a bigger cable gland will fit in a D-type hole, but the rectangular Neutrik shell I build these into are exactly the size of a D-type shell inside, so allowing for the nut part of the gland, the ones I show are the largest stock size that will fit easily without complex engineering. If you use the BNC D-type shell I show above (seems to have the widest internal opening diameter) and completely cut off the back with it's smaller hole for the BNC, you get a 20mm hole, and I have on other projects epoxy'd one of the 20mm Glands into that hole. A normal female D-type XLR also has 20mm ID, but current designs are offset and have cut-outs in the side.

[Jay Rose]

Of course there's also Studiohub, used in a lot of stations and available from almost any broadcast supplier.