Aux Input.
The front panel auxiliary input sockets may be switched between high level signals
(“LO GAIN”, suitable for active guitars and keyboards) and low level signals (“HI
GAIN”, suitable for microphones, pick ups or passive guitars), and are also controlled
by the input gain control.
LF Cut Filter.
The voice processor is equipped with high pass (low frequency cut) filter, which may
be used to remove unwanted low frequencies from the input signal. It is effective in
reducing hum, rumble caused by traffic or wind noise, and excessive LF signal content
from close mic applications.
Phase Reverse.
The phase reverse switch changes the polarity of the input signal. The effect is not
apparent with a single microphone setup, but is essential to correct any phase error in
a stereo application, or where the processor is patched into the insertion point of a
mixing console. A phase error typically appears as an apparent loss of bass.
Compressor Section.
Compressor Operation.
A compressor functions by reducing the gain of the signal when it exceeds a certain
level, or threshold. The amount of gain reduction may be fairly gentle through to
limiting, where the signal is clamped at the threshold level. The amount of gain
reduction is determined by the ratio control, which is calibrated as a ratio of the
output to input signals.
The gain of the signal is reduced by a voltage-controlled circuit. Variable time
constants are applied to the control voltage to adjust the rate at which the gain is
reduced, called the attack time, and the rate at which unity gain is restored after the
signal returns to below the threshold, referred to as the release time.
The effect of compression is to limit the dynamic range of a signal. It may be used to
keep a variable output from a bass guitar, for example, at an even level, or to add
punch to vocals, drums, guitar or a complete mix.
Whist the subjective sound quality can be improved by compression, the overall signal
level may be reduced. A gain make-up control at the output of the compressor stage
allows the signal level to be brought back to the same loudness as the uncompressed
signal.
