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:
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:
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.
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.
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.
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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