Sound Track: A Perfect Connection

Loren Alldrin
May 1997

Like water flowing through proper plumbing, your audio signals need good cables and connections to carry them from place to place.

Imagine the mayhem you'd have in your home if all your plumbing was installed wrong--really wrong. Your kitchen disposal feeds the bathtub faucet, the bathroom sink drains into the washroom hot-water tap and the toilet--well, you don't really want to know what the toilet's connected to.

If you picture your audio signal as water and your audio cabling as the pipes that carry it, you'll have a better grasp on the importance of wiring your audio lines correctly. Connecting audio cables wrong will give you the electronic equivalent of a glass of murky, brown water--your audio signals will carry all kinds of unsavory pollutants.

Before you can connect your equipment properly, you need to understand the various cables and connectors you'll encounter as you make and edit video. These come in various shapes, sizes and styles. Figure 1 shows you what they look like.

You'll usually have audio on one of four standard connectors: RCA, XLR, minijack or 1/4-inch. Each of these connectors can carry signals of various types in addition to audio, but that's the topic of another article.

The RCA jack is probably the most common audio connector in the consumer realm. It can carry video or audio, and is cheap to manufacture. It's not the sturdiest jack, though, and it's easy to disconnect accidentally. RCA audio cables usually come in pairs (often black and red in color) for carrying stereo audio. Using black for left and red for right is the easiest way to remember which is which, since both "red" and "right" start with "R."

The XLR jack is most commonly used for connecting microphones to mixers or recorders. The XLR mike jack carries a special balanced signal designed to reject noise. (Microphone signals are tiny and vulnerable, and need all the help they can get.) XLR jacks lock into place, making them much sturdier than RCA or 1/4-inch jacks. In most professional applications, XLR jacks carry all the audio--not just mike signals.

You'll find minijack connectors on microphone products designed for direct connection to the camcorder. Accessory microphones often use a minijack, as do many wireless microphone receivers. The minijack connector can be stereo or mono.

Though you may run across it occasionally, the 1/4-inch or "phone plug" connector is not as common in video production as it is in audio recording. Quarter-inch connectors usually carry audio from instruments, such as guitars and/or keyboards. They may also carry speaker-level signals on unshielded wire. Important note: never plug a speaker output into an audio input. You may fry your gear.

If you find yourself dealing with 1/4-inch phone plugs in your audio setup, don't fret: it's a simple matter to use an RCA-style adapter on a 1/4-inch signal cable. This configuration will work fine for most video applications.

Connecting audio lines is usually very straightforward. Outputs always go to inputs, and inputs to outputs. Wiring an output to an output won't harm your equipment, but it's a bit like trying to move a piano by pushing on both sides. Nothing happens. The same goes for wiring inputs to inputs.

As the complexity of your video system increases, making the proper connections gets harder. It's advisable, if you have a hard time picturing the signal flow in your head, to scratch out a rough diagram on paper. (See figure 2 for an example.) Keep this handy for when you need to remove, replace or bypass a piece of equipment.

If you've got your gear cramped into a small space without rear access, changing even one piece of equipment can be a real nightmare. The best solution is to use drafting tape or artist's tape to label each connector. Simply fold a 1.5-inch piece of tape all the way around the cable near the connector, and write the cable's destination on the tape. Drafting or artist's tape won't leave residue or harden like standard masking tape. When it comes time to change your setup, the tape labels save you having to trace out every cable. (I recently had to remove and replace an audio mixer with nearly 50 connectors attached. Thanks to tape labels, the swap took less than five minutes.)

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