Accessories: Part I

Direct Boxes

These are the most often-used accessories in sound system operation. Often referred to as "transformers" or "direct boxes" or "D.I. boxes," these little babies can make the difference between "sound" or "no sound." Special events can offer a wide variety of machines and instruments that need to be "plugged into" the sound system and "turned up." A direct box will take most, if not all, of these different signals and change them into an audio signal that looks like a microphone to the sound system. In technical terms, a direct box (usually with an internal audio transformer) will convert a high impedance, line or speaker level signal into a low impedance, microphone signal. This allows you to do two things. First, you can use existing microphone input jacks on the platform or wall. Second, you can send this transformed signal a much longer distance without any loss of quality of sound.

Here are a few things you can facilitate with a direct box:

• Keyboard/Synthesizer Outputs
• Bass or Electric Guitar Outputs
• Film Projector Speaker Outputs
• VCR or Computer Audio Outputs
• Cassette Deck or CD Player Outputs
• Portable Cassette Deck Speaker Outputs

The trick in getting the most out of any device is to understand how it works. Here's an example. During a recent musical production, a video recording was requested. The sound mixer had the capability of providing a separate blend or "mix," but the sound mixer was located in the audio/lighting booth. The video camcorder was located in the seating area. It was undesirable to have a long cable draped over seats or under the congregations' feet. BUT there were several microphone input lines that were located in the seating areas. The solution was to take the mixer output and feed it into a direct box (see Figure 1). We then disconnected the mic line from the mixer and plugged it into the direct box. At the other end, we took an adapter cable (see connector adapters below) and connected the microphone jack on the camcorder to the mic "input" jack that corresponded to the mic line our direct box was now plugged into (see Figure 2). Problem solved.

Set up for a microphone using a hardwire to the mixer.

Connector Adapters

There are as many connector adapters as there are types of connectors. That's obvious. What you need to know is which adapters will come in handy on a regular basis. Most of these items can be purchased in a ready-made form. Some adapters have a connecting cable between the two different connectors. Others are simply "barrel" adapters with a connector at each end. The most often-used adapters are:

• Three-pin male (XLRM) to three-pin male (XLRM)
• Three-socket female (XLRF) to three-socket female (XLRF)
• 1/4" in-line phone jack to 1/4" in-line phone jack (female to female). This item is available with two- or three-conductors.
• RCA phone jack (female) to 1/4" in-line phone plug (male)
• 1/8" mini jack to RCA plug or jack OR 1/4" phone plug or jack
• Banana plug to 1/4" phone jack (amplifier output adapter)

Test Tone Generators

This is a great device. And it's a lot less complicated than it sounds. The most prevalent model available is the Shure A15TG. This unit generates a simple 700 HZ tone at an approximate level of -40 dBV. This level is low enough to use for mic inputs and high enough to use in line level circuits. This tone generator can be used to troubleshoot sound system problems.

Let's look at a familiar example. The pulpit mic isn't working. Well, is it the mic itself? Or maybe it's the mic cable, or the mic input jack, or the sound mixer channel, or the sound mixer output, or the main equalizer, or the main speaker amplifier . . . ad infinitum. You know the feeling. With a tone generator, you can substitute it at any point in the system (up to the amplifier inputs) and locate the problem. Replace the "faulty" microphone with the tone generator. If you hear the tone over the sound system, you've found the problem: the microphone. If you still don't hear the tone, keep substituting the tone generator at each possible point of failure. When you finally hear the tone, you will have at least determined what DOES work. Then work backwards until you find the real culprit. It's simple and it works!! You will probably need to use some of the previously discussed adapters.

Continuity Testers (Cable Checkers)

These are the simplest form of measurement devices. They usually have an assortment of input and output connectors. When both ends of any cable are plugged into a tester of this type, the continuity of each connection, connector pins and the integrity of the cable conductors themselves are easily detectable. This is a very quick way to find out if a cable is bad - preferably before it is used. Using this device FIRST can prevent many problems, including equipment damage or failure.

Phone Sets

A modified phone handset can be used to listen to the outputs of many different components, including mixers, amplifiers and signal processing devices. The telephone company has been using this for years. Ready-made units are available for purchase.

Cable Tie Wraps

Basically, a cable tie wrap is a piece of velcro with one end permanently attached to a cable. This keeps cables from becoming tangled when they are put away.

Shock-Mount Microphone Clips/Mounts

Annoyed by footsteps on the platform being transmitted into the microphones? This is the answer.

Summary

This information is meant to bring your attention to some of the possible problem-solvers that are available. And this is just a starter list! Just keep in mind that if you are having a recurring, annoying problem, chances are someone, somewhere, makes an accessory to make your life a little less stressful.

by Ron Huisinga © 1996 Internet Sound Institute (www.soundinstitute.com). This article is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com

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