Effects and Signal Processors - Expander

Its functions are similar to those of gates, with the difference that instead of having an attenuation interval expressed in dB we have an expansion-ratio. Its functions are illustrated in the following expansion curve:

Expansion Curve

Beneath the threshold the signal is amplified in accord with an expansion-ratio value. Above the threshold the input signal proceeds unvaried to the output.

The following is the sound of snare drum before and after the application of an expander (the applied expansion is, in this case, very pronounced, to the point of sounding unnatural).

Drum-kit snare drum [Track 45]

Drum-kit snare drum with expander [Track 46]

In this case the expander amplifies the lower sounds, whereas it leaves those that go beyond the threshold unvaried. The following diagrams compare the two envelopes (a single beat of a snare drum has been chosen for this example).

Envelope of a single beat of a snare drum

Envelope of a single beat of a snare drum with expander