Using Audio Stage Snakes
Normally in commercial snakes, you find 8 to 16 XLR connections and 2 to 4 unbalenced conections in a metal box, that sits on, or near, the stage. The XLR's are for mixer inputs - usually microphone or other gear that connects to 'Direct Boxes' (high impedance unbalenced in, low impedance XLR out). The Unbalenced connections are used to send signals from the PA Mixer back to the Stage - these are typically the output of the Mixer for the main Power Amps, and a mix for the floor monitors. This allows you to keep your Power Amps closer to the speakers, avoiding losses caused by the wires to the Speakers from the Power Amps.
A very simple snake configuration would be as shown below - 2 XLR connections and 2 unbalenced connections.
It would be used in the following way:
As you can see there are many signal paths in this drawing. The Microphones connect to the Snake Box on the stage thru XLR connectors. The Microphone signals now flow to the PA Mixer. At the mixer, the Sound person adjusts the levels for both the main speakers and the floor monitors. These 2 levels are sent back to the Snake Box on the stage. The Main Speaker mix goes into the Power Amps that are used to provide the sound for the audience to listen to. The Floor Monitor mix is sent to the power amps that are used to provide the sound for the performers on the stage.
This configuration allows someone 'out front' to manage the sound mix, based on what it all sounds like - usually, the sound mixer is 25 to 50 feet (8 to 16 meters) from the performers - any closer and it will be hard to really tell if its mixed well or not. For outdoors shows, the PA mixer board and sound crew may be quite a bit further back from the stage - the set up doesn't change, just the length of the cables used in the snake.
You will find that often 1 or more of the snake channels is not working, like any other cable, it can break - this usually happens at the end that connects the PA mixer, most often in systems that are moved frequently. You can also easily damage the cable bundle by dropping something heavy on it, or rolling something heavy over it - cable is expensive - protect your snake cable bundle. Because it is common to experiance 1 or more non-operating channels, it is in your best interests to have 2 spare XLR inputs and 1 spare unbalenced input in any snake that you make or buy.
When buying or building a snake, the cable quality will be the largest expense, followed by the cost of the XLR connectors. Always buy the best cable that you can afford and protect your hardware at all times. Unless you can find a great deal on quality cable, you may not save much money by building your own snakes, however, if you need to create a special configuration, making your own is probably the only solution available to you.
Maximum Cable LengthsFor Balenced Low Impedance XLR (microphones), 200 feet is a common length to limit the cables to, however the length of a US football field (100 yards/300 feet) is often done by the pros for outdoor and stadium concerts.
High Impedance signals (guitar, for example), are limited to 25 feet or less because of noise - you need to plug these into a DI box on the stage and convert them to Balenced Low Impedance XLR signal for the long distance to the PA amplifier. Alternately, most people use a low impedance microphone set approx 1 foot away from the front of a guitar amplifiers speaker - PA systems typically make for poor sounding guitar amplifiers if you connect directly to them.
Shielded Mixer output signals (line level - 100 to 600 ohms low impedance) are ok at 200 to 300 feet (these are the signals that go back to the power amps on Stage).
See Building Audio Snakes for more information on general construction.
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