12
COMPRESSOR THEORY OF OPERATION
Compressor Basics
Before we dig in to a description of the compressor circuit, it is useful to examine the general characteristics of
compressors and review some terminology. The chart below depicts the input/output characteristics of a com-
pressor, an expander and a perfect amplifier. When operated within its specified range, an amplifier provides a
constant amount of gain regardless of the level of the input signal. In figure 4 below, the middle line depicts a
perfect amplifier with a gain of 10 dB. To see this, notice that a signal with an input level of -30 dB will result
in an output level of -20 dB, which is an increase of 10 dB. Similarly, an input level of 0 dB will result in an
output level of 10 dB, hence the gain stays fixed at 10 dB regardless of the input level.
INPUT/OUTPUT CHARACTERISTICS OF A COMPRESSOR, AN EXPANDER AND A PERFECT AMPLIFIER.
