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The Basics Of Analog & Digital Cabling For Professional Audio

A system is only as good as its cables, interconnects, snakes, and networks -- period

Many snakes have the capability to run signals from and to the stage. The “sends” are for the mic inputs to the mixer and the “returns” get the output of the mixer to the amp rack or powered loudspeakers. Larger systems may use a separate return snake for the line-level outputs to keep any crosstalk (interference from adjacent snake channels) to a minimum.

Splitter snakes provide more than one output off the send side of a snake, so the same inputs can be sent to multiple consoles (i.e., when using a separate monitor or broadcast console along with the house console). Some splitters are passive and simply hardwire a “Y” off each channel.

A better practice is to use isolation transformers to isolate each console from potential noises and hums and buzzes caused when plugging them into different power sources. In a split snake system, usually one split is hard-wired to the inputs so that the console can pass phantom power to mics and DIs.

Another version, called a “power snake,” combines a few loudspeaker lines along with the signal channels. These can work well for a small system on short runs but their use is usually limited to about 100 feet.  Yet another multi-circuit version that has become popular recently is cable systems that include signal and power in one jacket. These are perfect for getting audio and AC power to a powered loudspeaker or floor wedge.

Networked World

While analog cables still fill the road trunks, digital systems are starting to take over many of the audio transport duties. They offer a host of signal routing benefits that analog simply can’t match, including using a small thin cable to route multiple channels of audio. Smaller cable equals less stagehands required to lay out a digital network as opposed to large, heavy multi-core snakes.

Digital cables are also less prone to RFI and crosstalk. Networks, as we now call our digital transport systems, can offer audio almost anywhere along the line, and can easily interface with multi-track recording systems, personal monitoring rigs and broadcast trucks.

Transport networks use one of three types of cable: fiber optic, coax or Ethernet Cat-5/6. Coax cables offer up a rugged solution and are used by a few manufacturers to transport signals between stage boxes, consoles and recorders. Fiber optics offer the ability to send signals over very long distances, and because the signals travel as light, are immune to all outside electromagnetic disturbances and RFI. Ethernet Cat-5/6 cables are the most popular, found in many different systems to transport audio at distances of up to about 330 feet (100 meters). Some of these have accessories that can extend this distance.

A typical molded RJ45 connector (left) with an Ethercon connector.

Ethernet cables have RJ45 8-pin connectors that are stout enough for home computer use but not rugged enough for most gig uses, so they’re best replaced with rugged Ethercon connectors that surround the plastic crimp-on with a metal barrel that provides added protection in addition to better locking.

Ethernet cables come in a variety of styles. Some have solid wire conductors that offer the best performance, while others have stranded conductors that provide greater flexibility. They can be unshielded but it’s better to go with shielded in noisy environments.

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Ethernet cables can also be wired in different ways. The “standard” wiring scheme runs pin 1 to pin 1, pin 2 to pin 2, etc. “Crossed over” cables wire pin 1 to pin 3, pin 2 to pin 6, pin 3 to pin 1 and pin 6 to pin 2. Before choosing an Ethernet cable, check manufacturer recommendations on which cable is recommended for interconnection of specific gear.

As noted earlier, a downside to digital transport is that there is the need for analog to digital conversion, and further, manufacturers utilize a variety of variety of different protocols that are not compatible. However, that’s been changing rapidly, as more and more devices support multiple protocols, and the Audinate Dante protocol in particular has really caught on the past few years. And, AVB (Audio/Video/Bridging) is a standard that manufacturers are also starting to embrace. The bottom line is that our job of interconnecting various gear from various manufacturers is getting easier.

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