Harman MPMi, User Manual

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GLOSSARY
AFL After-fade listen: a function that allows the operator to monitor the post-fade signal
in a channel independently of the main mix.
Auxiliary send An output from the console comprising a mix of signals from channels derived inde-
pendently of the main stereo mix.
Balance The relative levels of the left and right channels of a stereo signal.
Balanced A method of audio connection which ‘balances’ the wanted signal between two wires,
these wires also have a screen which carries no signal. Any interference is picked up
equally by the two wires, which results in cancellation of the unwanted signal. In this
guide, the term can refer to various circuit architectures. Connection details are given
in relevant sections.
Clipping The onset of severe distortion in the signal path, usually caused by the peak signal
voltage being limited by the circuit’s power supply voltage.
DAT Digital Audio Tape, a cassette-based digital recording format.
dB (decibel) A ratio of two voltages or signal levels, expressed by the equation dB=20Log10 (V1/
V2). Adding the suffix ‘u’ denotes the ratio is relative to 0.775V RMS.
DI(direct injection)/DI Box The practice of connecting an electric musical instrument directly to the input
of the mixing console, rather than to an amplifier and loudspeaker which is covered
by a microphone feeding the console.
Equaliser A device that allows the boosting or cutting of selected bands of frequencies in the
signal path.
Fader A linear control providing level adjustment.
Feedback The `howling’ sound caused by bringing a microphone too close to a loudspeaker
driven from its amplified signal.
Foldback A feed sent back to the artistes via loudspeakers or headphones to enable them to
monitor the sounds they are producing.
Frequency response The variation in gain of a device with frequency.
Gain
The amount of amplication in level of the signal.
Headroom The available signal range above the nominal level before clipping occurs.
Impedance balancing A technique used on unbalanced outputs to minimise the effect of hum and interfer-
ence when connecting to external balanced inputs.
Insert A break point in the signal path to allow the connection of external devices, for instance
signal processors or other mixers at line level signals. Nominal levels can be anywhere
between 0dBu to +6dBu, usually coming from a low impedance source.
Pan (pot) Abbreviation of ‘panorama’: controls the levels sent to left and right outputs.
Peaking The point at which a signal rises to its maximum instantaneous level, before falling
back down again. It can also describe an equaliser response curve affecting only
a band of frequencies, (like on a graphic equaliser), “peaking” at the centre of that
band.
Peak LED A visual indication of the signal peaking just before the onset of clipping, which will
distort the signal.
PFL Pre-fade listen: a function that allows the operator to monitor the pre-fade signal in
a channel independently of the main mix.
Phase A term used to describe the relationship of two audio signals. In-phase signals reinforce
each other, out-of-phase signals result in cancellation. Phase is a measurement of
relative displacement between two waves of identical frequency.
Polarity A term used to describe the orientation of the positive and negative poles of an audio
connection. Normally connections are made with positive to positive, negative to nega-
tive. If this is reversed, the result will be out-of-phase signals (see ‘phase’ above).