Introduction to Computer Music: Volume One

2. Cables and Connectors

RCA (phono) with single-conductor shielded cable: for consumer (e.g., home stereo) and some studio gear, such as cassette or CD player.
1/4-inch mono phone (TS - Tip/Sleeve) with single-conductor shielded cable: used to connect synthesizers, electric guitars, and signal processing gear to mixing consoles. Unbalanced, so long runs susceptible to interference and ground loops between equipment.
1/4-inch stereo phone (TRS - Tip/Ring/Sleeve) with two-conductor shielded cable: can carry stereo signal or mono balanced line (see below). Found at end of stereo headphone cables and used to connect professional balanced gear to a mixing console. A special variety of TRS jacks with a smaller tip, sometimes called patchbay or military, are designed specifically for patchbays. Using the non-military types may, over time, damage the patchbays designed for the military-style jack.
XLR (Cannon) connectors (male left, female right) are normally used with two-conductor shielded cable. XLR connectors have three pins or sockets (male or female, you'll figure it out). Used for microphones or high-quality balanced equipment (such as DAT players). The cables are usually male to female, so they can be extended by connecting one to another. A locking mechanism requires you push down a tab to release them. Absolutely the best choice for long cable runs.
A snake is a bundled set of many cables often ending in a box of connectors. Designed primarily to run multiple microphone cables from a central point on a stage to a mixer. Many snakes (such as the one pictured) combine XLR and 1/4-inch connections.

A balanced line is a two-conductor shielded cable connected to a balanced input. The two conductors carry the same signal, but with reverse polarity (meaning that one conductor carries a signal that is the mirror image of the other). If external noise and interference enters the cable, it will probably affect both conductors equally. The input stage flips the polarity of one conductor, and combines the two conductors. This cancels out the noise and interference. Generally, balanced mixers and gear are more expensive due to the additional circuitry. The more typical single-connector connection with 1/4" mono jacks is unbalanced and hence more susceptible to interference.

A patchbay is a central location of strips of connectors, directly comparable to a telephone switchboard (in fact, most older patchbays are derived from telephone patching equipment.) Inputs and outputs of devices can be connected with patch cords, providing flexibility in studio connections without the need to disconnect and reconnect cables directly to equipment for different operations. Here a student is hard at work patching in the early CECM studio.

Patchbays can be normalled, normalled-through, or half-normalled . These are arrangements by which two components (usually the most frequently-used connection) are automatically connected (hard-wired) without patching. Inserting a patch cord into either the input or output jack corresponding to either device will break the normal connection. Half-normalled means one or the other of those connections will not be broken. The CECM Studio A patchbay is half-normalled.

A multi or multiple -- you'll be laughed at if you say "multiple" around a studio engineer -- is a set of jacks on a patchbay wired to connect to each other. This is an easy way to split a signal into more than one path.

A direct box (or D-box, or DI box) is an impedance-matching device usually used to send either an electric guitar (high impedance) or contact mike signal a long distance to a mixer (low impedance) without interference. Some active direct boxes can be powered by phantom power from the mixer.

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