Clear Path: Analog Snake Systems And Their Applications
Back in 1996 - more than 15 years ago - I predicted that the good old analog snake would be gone, soon to be replaced by digital counterparts. But something strange happened…the world did not change.

November 27, 2013, by Peter Janis

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Back in 1996 - more than 15 years ago - I predicted that the good old analog snake would be gone, soon to be replaced by digital counterparts. But something strange happened…the world did not change.

As both a manufacturer of snakes and a distributor to the Canadian market, we sell more analog snakes today than ever before. With that in mind, let’s have a look at analog snakes and their application. There are basically two formats: traditional floor boxes or rack-mount snakes.

The floor box is less expensive, generally has fewer features, and is maybe a little less sexy. It’s less expensive to eliminate expensive multi-pin connectors by attaching the cable directly to the snake head. This is usually stored together with cabling in a large case.

Rack-mount snakes are usually split into two, with the head stored in one case and the cable in another.

These are generally outfitted with multi-pin connectors and more “concert specific” options. System techs find the upright positioning of rack-mounted snakes to be easier to use with less spaghetti to sort through in times of need.

Most concert snakes are set up with a 200- to 300-foot (75- to 100-meter) multipair cable (trunk) for front of house and a 50-foot (15-meter) trunk for monitors. These are “Y’d” via simple hardwire or “split ” via isolation transformer. A ground lift switch is usually on the monitor out.

Applications of analog snake systems.

Some trunks have the XLR break-out splay attached, while others employ a multi-pin at the breakout that allows the splay to remain inside the console dog-house. The size and magnitude of the snake can vary immensely depending on the situation, and they can be scaled depending on individual needs.

Types Of Cable
Most snakes employ twisted pair balanced wire, the same type of cable that telephone companies have used for 100 years to transmit phone calls thousands of miles across the continent. Twisted pair is highly immune to electro-magnetic fields and well suited for these relatively short runs.

These are usually shielded with a foil wrap (and drain wire) to further reduce noise from RF contamination. Better snake systems are equipped with RF filtering circuits to further reduce noise that is emitted from lighting dimmers, power transformers, and electrical systems.

Trade-offs with cable are size and performance. Back in the early days, folks used to use Mogami - a very flexible recording cable - for concert touring. Their idea was to get lower capacitance cable for maximum high-frequency performance. But this cable corkscrewed in no time because it was too soft.

At the other extreme, we’ve built snakes for use in the arctic (literally). These are quite stiff when warm, but would remain somewhat flexible in sub-zero temperatures, and as you might imagine, this type of cable is very difficult to deploy. A nice balance between ruggedness and flexibility is preferred.

Today, most touring companies opt for 50 or so audio channels with individual PVC jackets that hold the shield in place.

The classic multi-pin connector.

This is extruded “hot” so that it embeds itself into the outer jacket to resist corkscrewing. A cable with a 1-inch (2.5-centimeter) OD (outside dimension) is usually preferred as it is relatively easy to handle while having sufficient channel capacity.

Most concert touring companies employ a separate drive snake, which keeps high level signals away from more sensitive mic levels which helps reduce cross-talk.

Multi-pin Connectors
Multi-pins connect the snake trunk cable to the snake head and splay, with the two most popular connectors being Mass and Veam.

Originally developed by Cannon for the oil exploration industry, the Mass connector is a screw-on connector that comes in 122 pin (40 channels) and 176 pin (56 channels) formats in a hermaphroditic configuration with half of the pins male and female.

The advantage with the hermaphroditic design is that you can deploy the cable from either end. The downside is that the pins are relatively small and one has to be careful when mating as misalignment will cause damage.

The C5015 Mil Spec developed by the U.S. military employs a quartertwist bayonet connection with a rugged circular metal body in a variety of pin configurations that often range from 37 pins (12 channels) to 201 (66 channels). The most common used on concert snakes is a 150-pin (50 channels) design originated by Veam and now offered by a number of companies.

The benefit of the circular bayonet is that the pins are larger and easy to replace due to the rubberized pin insert. The 201-pin option allows for more channels, but cable size and pin fragility should be considered.

Custom shops build snakes using all of these. Considerations when selecting a multi-pin connector includes compatibility with older snakes, crossrental opportunities with other sound companies in your area and personal preference based on experience with a given product.

Snake “heads” come in a multitude of sizes, varieties and capabilities.

With more than 150 wires crammed into such as small space, multi-pins are time consuming to wire and repair. Outfitting the snake with a proper Kellems Grip strain relief will protect the sensitive wiring inside the connector and reduce field service.

Snakes & Splitters
Most concert snakes are in fact splitters. What this means is that the signal from the stage microphones and direct boxes are split to feed the house mixer and monitor mixer.

Often these are set up with an auxiliary output that can be used to feed a broadcast truck or recording system. And with more bands using backing tracks and computers, we find that 48 channels is now the minimum used for most productions.

As the XLR connector is the only ‘standard’ in balanced professional audio, it’s a really good idea to outfit the snake with an XLR panel or a spare trunk with XLR outputs. Broadcasters are well familiar with the problems of hum and buzz that plague most stages and therefore will generally have a transformer isolated input panel at the truck.

This leads to a discussion on transformers. Audio transformers allow audio to pass while blocking DC. They also allow the ground to be disconnected between consoles, thus eliminating ground loops. Good quality transformers are expensive but they sound much better (less distortion, more linear, less phasing) and can save countless hours of trouble shooting as they eliminate noise.

Normally, the house console is connected directly to the microphone, thus providing a return path for 48-volt phantom power for condenser mics and direct boxes while the monitors will be isolated. To save money, some sound companies will opt for a “Y” or hard-wire split whereby the microphones wires are simply wired in parallel to feed the monitors and the ground is disconnected. This can work, but is prone to noise and ground loops.

Passive Versus Active
Transformers do not require any form of power to make them work. They are passive. Mic bridging (or splitter) transformers are available with 1, 2 or even 3 isolated outputs.

The more splits, the more expensive. This sometimes leads to companies opting for active splitters, which employ preamp circuits (like the ones in your mixer) to buffer the microphone signals. When an active splitter is employed, the preamp essentially moves from the mixer into the snake.

This also applies to digital snakes. In other words, the sound of your expensive mixer has now been replaced by low-cost ICs. Transformers and active buffers react very differently when they’re overloaded. When active circuits are hit hard, they distort causing a very harsh sounding square wave (clipped output).

When transformers are hit hard, they saturate. Good ones such as those made by Jensen round out the sound in a more gradual way, rendering a warmer tone.

A point of contention with digital snakes is “who” is in control. With a passive snake, each mixing desk is directly coupled to the electrical output from microphone. Many system techs prefer passive snakes because it allows each engineer to set the mic levels based on their needs.

For instance. when controlling levels for in-ear monitors, having the house engineer turn up the trim level without notice can cause serious ear damage to the artist on stage. (And sometimes the monitor engineer’s job.)

A serious gamut of analog snake and other interconnect found on typical live sound applications.

And although one cannot deny the appeal of deploying a single fiber versus and a big fat snake cable, when a snake cable fails it is usually only one channel that goes down, not the catastrophic problem of a complete system failure.

Analog snakes can be repaired with a soldering iron while digital alternatives require the band to carry a spare and extra logistical planning to return the down unit to the factory. For many, field serviceability is a primary concern.

It’s important to note that most signals traveling around a stage are mic level, including the output from the many direct boxes that are used to feed bass, acoustics and keyboards to the PA system. By ensuring all levels are the same, should a channel fail, it is simply a matter of re-patching to a spare. This “standard” practice makes it easy and quick to resolve issues, especially when 20,000 fans are waiting to be entertained.

Modular Versus Flat Panel
For decades, snake manufacturers have been producing flat-panel snakes that mount all of the XLR connectors on the front panel with multi-pins below. This is the most economical method of producing a snake.

More recently, there has been a shift towards modular designs that enable the user to reconfigure the system to adapt for future needs. The benefits with modular designs include being able to add extras such as sub-snakes, cross-patching capabilities, or extra outputs for broadcast and recording feeds.

Being able to quickly replace an input strip should field service be required is an added benefit. The down-side is a higher cost at the outset due to added metal work and electronics employed to produce the frame and individual channel strips.

When on tour, 99 percent of all problems can usually be traced to cold solder joints, faulty wiring or second rate connectivity due to bad cables. Truck vibrations are particularly hard on equipment. And the biggest monster of all is the snake system. If your interconnect system fails, you’re late for dinner or worse, you may lose the gig.

The snake system is the umbilical cord that brings it all together and should not be skimped on.

Peter Janis is president of Radial Engineering, which has supplied analog snakes to venues and sound companies such as Cirque du Soleil, Grand Ole Opry, Solotech, Masque Sound, Canadian Broadcast Corporation, CBS (Sony), and The House of Blues.



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Clear Path: Analog Snake Systems And Their Applications
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