LIVERPOOL Tube Compressor
Page 9
1. Input Gain Control:
The input control has a dual function. This control is used to adjust the
input level and to provide the desired average compression as indicated
on the compression meter. The input control on the LIVERPOOL is located
ahead of the tubes and directly after the input transformer. So as you
advance the input control, you're hitting the input tube, which is the gain
reduction stage, with more and more signal. The signal is then amplified
by the second stage. The control signal is taken from the output of the
second stage then rectified into a negative control voltage (CV). Gain
reduction is done by making the DC bias on the first stage tube more
negative. So as the input is increased so does the CV and therefore the
amount of compression. The onset of compression is determined by the
threshold and how far the input control is advanced. The input tube has a
limit as to how far it can be biased negative to reduce gain before it goes
non-linear, and since your audio signal is obviously swinging both positive
and negative, the big swings of the audio signal plus the negative gain
control voltage will eventually push the tube into cut off. The limiting
characteristics shouldn't change much, but the distortion characteristics
will. Distortion can be creatively used by turning up the Input and turning
down the Output while using very little or no compression.
