Building an Audio Snake

Updated with some additional suggestions about construction on 2/02 and 4/04

The Audio Snake design used here uses seperate cables for each signal bundled into a cluster of wires. To avoid Ground Loops (Which cause hum) there is only one chassis connection to the Stage Side Box, and that shares the Sheild wire of the first XLR connector. Also, on the metal chassis, the 1/4 inch phone jacks are isolated from the chassis by mounting them onto a plastic plate.

As you can see there are many distinct signal paths in this drawing. This is the Stage Snake Box. You will note that the XLR's all are wired independant of each other, as well as the 1/4 inch phone jacks. The only signal connection to the metal chassis is the green wire that attaches to XLR connector A on pin 1.

The Mixer end of the Snake splits out to 6 signal connections and there is a green wire from the A male XLR connector that can be used to attach to the ground point on your mixer.

NOTE: Not all mixers have ground points, and you don't always need to hook a ground up to the chassis, however, it may reduce noise and eliminate some instances of electrical shock problems, so, a good snake will have a ground point of some sort. Make sure that your ground point wire is long enough to reach the mixers ground point when the A XLR cable is plugged in - usually 12 inches (30 cm) is a good length. Use it as you need it.

This Design requires that you bundle up the 6 seperate cables into a single bunch. There are many ways to do this. Some common ways:

• Black Electrical Tape
• Plastic webbing that pulls tight around the cables
• Plastic wire ties every 6 (15 cm) to 12 inches (30 cm).
• Small nylon cord.

NOTE: When you tightly bundle cables with Wire Ties, its possible that you can get 'cross-talk' - this occurs because the wires are forced close to each other and act as transformer, coupling the audio signals to each other - lots of wire ties means that you can have lots of coupling points. Do not make the wire ties too tight. Another option is to use a woven mesh tubing - I got this source and advice from Patrick Gregston in an email:

Tight binding creates kinks in the wire in such a way that it actually induces noise. A single cable cinched at regular intervals will distort a sine wave. The more regular the cinches, the more potential for screwing up the signal.

TechFlex (http://www.techflex.com) was my first and still favorite manufacturer. They have a huge variety, sell online, but can be pretty pricey unless you buy whole spools.

The main trick about using such sleeves - unless you get the one with the velcro seam - is to put all the connectors in a plastic bag, staggered so they have a relatively narrow circumference. Adjusting them to similar lengths isn't difficult in runs under twenty five feet or so. Also cutting them with a small torch or hot wire makes nice clean ends. Using scissors means that you will have frayed messy openings soon. Stress relief without binding can be challenging too.

The Bundle should seperate at the Mixer end at around 6 feet (2 meters).

Needless to say, many different types of cable can be used for this function, however, for this design I chose to use easy to find, common 2 conductor sheilded wire and 1 conductor sheilded wire. You'll note also that the lengths of the cables are not given - thats up to your needs. Anything less than 25 feet (approx 8 meters) is not tremendously useful. 50 (16 meters) to 100 feet (32 meters) are very common.

One additional argument for having a number of Snakes with only a few XLR connectors on them would be for recording. Many times I've put a drummer in a room all by themselves, so I need a seperate snake for that. I have also placed singers in a tiled wall bathroom for sound isolation (and natural reverb) then fed a signal back thru to their headphones to listen to while they sing their parts. You can build them anyway that suits your needs.

Some additional construction thoughts

The actual Snake cable wire

• You need stranded wire - this allows the wire to flex. Solid wire is designed to be built into things and not moved much. Do not use solid wire in your Snake cable.
• Sheilded pair for low level audio signals (ie. signals from your microphones need a sheild). This sheild could be aluminum foil with a single wire wrapped around it in the wire, or it could be light copper wrapped around the signal wires or a woven shield. However its done, a sheild needs to surround the signal wires.
• The cable has to be able to be stepped on and abused. This will happen a lot.
• The stranded signal carrying wires will not carry a lot of power so, 20 to 24 gauge will work fine.
• The upper limits for general snake length are 200 to 300 feet. The longer it gets, the better the cable needs to be (very low capacitance!).

A lot of people have asked me about using CAT 5 cable for thier snake. It conflicts with most of the above properties. It may be cheap and have wonderful data carrying capabilities, but its not appropriate for this use.

Finding XLR Connectors

http://www.partsexpress.com has XLR connectors, but once again, many surplus houses (some are online, such as http://www.meci.com) have XLRs too and you can often get them very inexpensivly if you look.

NOTE: In order to avoid ground loops caused by 1/4 inch jack cables plugged into the stage end of the Snake Box, you may need to build some cables that do not have the sheild connected at both ends of the cable (the sheild needs to be connected on at least one end) - this issue is outside of the context of this article, however, it is an issue that may crop up from time to time. See Ground Loop PA Advice and Rane - Sound System Interconnection for some good information on the topic.

Questions? Comments? .

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