User Manual

73
Soundcraft Si Expression User Guide V1.0 0213
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 negative.
If this is reversed, the result will be out-of-phase signals (see ‘phase’ above).
Post-fade The point in the signal path after a fader and therefore affected by the fader position.
Pre-fade The point in the signal path before a fader, and therefore unaffected by the fader position.
Ratio The amount by which a compressor squashes a signal when compressing expressed as a
ratio. 1:1 means no compression (1db input level increase to the compressor = 1db ouput
level increase from the compressor) 12:1 (12dB input level increase to the compressor
= 1db ouput level increase from the compressor)
Rolloff A fall in gain at the extremes of the frequency response.
Shelving An equaliser response affecting all frequencies above or below the break frequency i.e.
a highpass or lowpass derived response.
Solo An almost generic term used to describe PFL or AFL functions.
Spill Acoustic interference from other sources.
Threshold Limit above which a process will start, usually used in relation to dynamic processors
such as compressors or gates to set the level at which compression will start or the gate
will open
Transient A momentary rise in the signal level.
Unbalanced A method of audio connection which uses a single wire and the cable screen as the signal
return. This method does not provide the noise immunity of a balanced input (see above).
+48V The phantom power supply, available at the channel mic inputs, for condenser microphones
and active DI boxes.