Empress Effects Compressor - Manual (Page 3)

The Basics of Compression
Compression can add consistency and sustain to your playing or it
can be used to add note definition and other effects. It essentially
narrows the difference between high and low audio levels by
reducing the gain to any signal over the threshold.
The ratio determines how much
gain reduction will be applied to
the signal once it crosses the
threshold. At a 4:1 ratio, for
every 4dB of input signal above
the threshold, there will be 1dB
of output signal. A 10:1 ratio
would output 1dB for every
10dB of input signal, etc.
Attack controls how quickly the gain reduction will begin after a
signal has crossed the threshold. Release controls how long it takes
for the compressor to return to its initial level after the signal drops
below the threshold.