PreSonus ACP22 - Manual (Page 8)

Controls & Connections
2.1 Front Panel Basic Layout
Notice that the front panel is divided into two identical sections. These
are the two signal processing channels of the ACP-22. Each channel
contains:
· Compressor/Limiter;
· Noise Gate;
· Gain (output control);
· Link & Bypass Control.
2.2 Compressor Controls
Threshold
The Compressor threshold sets the level at which the onset of
compression begins. When the signal is above the threshold setting, it
becomes 'eligible' for compression. Turning the threshold knob counter-
clockwise causes more of the input signal to become compressed if you have
a ratio setting of greater than 1:1.