Mackie M1200/M1400 owner manual APPENDIX B: Glossary

APPENDIX B: Glossary

This Glossary contains brief definitions of many of the audio and electronic terms used in discussions of sound mixing and recording. Many of the terms have other meanings or nu- ances or very rigorous technical definitions which we have sidestepped here because we figure you already have a lot on your mind. If you’d like to get more information, you can call Mix Bookshelf at 1-800-233-9604. We recom- mend the following titles: The Audio Dictionary, by Glenn White; Tech Terms, by Peterson & Oppenheimer; Handbook for Sound Engineers, by Glen Ballou; Mackie Mixer Book by Rudy Trubitt; and Sound Rein- forcement Handbook, by Gary Davis.

balanced

In a classic, balanced audio circuit, the two legs of the circuit (+ and –) are isolated from the circuit ground by exactly the same imped- ance. Additionally, each leg may carry the signal at exactly the same level but with opposite po- larity with respect to ground. In some balanced circuits, only one leg actually carries the signal, but both legs exhibit the same impedance char- acteristics with respect to ground. Balanced input circuits can offer excellent rejection of common-mode noise induced into the line and also make proper (no ground loops) system grounding easier. Usually terminated with 1⁄4" TRS or XLR connectors.

bandwidth

The band of frequencies that pass through a device with a loss of less than 3 dB, expressed in Hertz or in musical octaves. Also see Q.

bus

An electrical connection common to three or more circuits. In mixer design, a bus usually carries signals from a number of inputs to a mixing amplifier, just like a city bus carries people from a number of neighborhoods to their jobs.

channel

A functional path in an audio circuit: an in- put channel, an output channel, a recording channel, the left channel, and so on.

clipping

A cause of severe audio distortion that is the result of excessive gain requiring the peaks of the audio signal to rise above the capabilities of the amplifier circuit. Seen on an oscillo- scope, the audio peaks appear clipped off. To avoid distortion, reduce the system gain in or before the gain stage in which the clipping oc- curs. See also headroom.

console

A term for a sound mixer, usually a large desk-like mixer.

crest factor

The ratio of the peak value to the RMS value. Musical signals can have peaks many times higher than the RMS value. The larger the transient peaks, the larger the crest factor.

dB

See decibel.

dBA

Sound Pressure Level (SPL) measured with an “A” weighting filter.

dBm

A unit of measurement of audio signal level in an electrical circuit, expressed in decibels referenced to 1 milliwatt. The “m” in dBm stands for “milliwatt.” In a circuit with an im- pedance of 600 ohms, this reference (0 dBm) corresponds to a signal voltage of 0.775 VRMS (because 0.775 V across 600 ohms equals 1mw).

dBu

A unit of measurement of audio signal level in an electrical circuit, expressed in decibels referenced to 0.775 VRMS into any impedance. Commonly used to describe signal levels within a modern audio system.

dBv

A unit of measurement equal to the dBu but no longer in use. It was too easy to confuse a dBv with a dBV, to which it is not equivalent.

dBV

A unit of measurement of audio signal level in an electrical circuit, expressed in decibels

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