LA Audio C400 - Manual (Page 5)

Page 5
2.0 DESCRIPTION OF CONTROLS
2.1 BYPASS switch
Pressing BYPASS cancels compression by removing the side chain voltage from
the voltage controlled amplifier (VCA). The Input-Output and level change
circuitry remain in the signal path.
The BYPASS led lights when the compressor is Bypassed.
2.2 PROG. switch
The PROGRAM switch inserts a low-cut filter into the side chain to remove the
bass content of the program material which can cause over compression or
pumping.
The filter response makes the side chain 6dB less sensitive at 100Hz.
2.3 THRESHOLD control
In HARD knee mode THRESHOLD sets the reference level above which signal
compression starts. The RATIO control then adjusts the amount of compression
applied to input signals above threshold.
In SOFT knee mode, compression occurs gradually over a 10dB range of input
signal level. The indicated THRESHOLD level is approximately in the centre of
this range and the slope set by the RATIO control will not be reached until the
signal level has increased some way above the threshold - see Fig 2.1 and 2.2.
Control range is -40dBu to +20dB.
2.4 RATIO control
RATIO controls how much compression is applied to an input signal once it has
increased above threshold and refers to the final compression slope.
The RATIO markings around the control indicate how many dB the input signal
must increase to cause a 1dB rise in output level. A RATIO of 2:1 means the
input has to increase by 2dB for a 1dB change of output level. A 4:1 ratio requires
a 4dB increase of input level for a 1dB change of output, etc.