PreSonus ACP88 User Manual
Page 8
CONTROLS & CONNECTIONS
5
2.2 Compressor Controls
• Threshold
The Compressor Threshold sets the level at which compression begins. The below and
above LED’s over the Threshold knob indicate whether the input signal is below or
above the Threshold setting. When the signal is above the Threshold setting, it
becomes ‘eligible’ for compression. Basically, as you turn the Threshold knob counter-
clockwise, the input signal is compressed. (If you have a ratio setting of greater than
1:1.)
• Ratio
Ratio sets the compression slope. This is defined as the output level versus the input
level. For example, if you have the Ratio set to 2:1, any signal level above the Threshold
setting will be compressed at a compression ratio of 2:1. This simple means that that for
every 1dB of level increase into the compressor, the output will only increase ½ dB, thus
producing a compression Gain reduction of 0.5 db. As you increase the Ratio, the
compressor gradually becomes a limiter. A limiter is defined as a processor that limits
the level of signal to the setting of the Threshold. For example, if you have the
Threshold knob set at 0 dB, and the Ratio turned fully clockwise, the Compressor
becomes a Limiter at 0 dB. This means the signal will be limited to an output of 0 dB
regardless of the input signal.