Expander

Purpose

The expander provides a means of exaggerating the dynamics in an audio signal.  The expander is often used as a single ended noise reduction device.

The only difference between the Expander and the Compressor is that the expander produces gain reduction when the input signal is below the Threshold Level while the compressor produces gain reduction when the input level is above the Threshold Level.

Whereas the compressor begins to operate as a Limiter at extreme compression ratio settings, the Expander begins to resemble a Gate as the expansion ratio is increased.

Controls

Expansion Ratio

The Expansion Ratio control adjusts the severity of gain reduction produced by the expander when the input signal is below the Threshold Level.

Dynamic variations in the input signal will be exaggerated by a factor equal to the Expansion Ratio.

Tip: When the Expansion Ratio is set above 5, the expander may be considered to be operating as a Gate.

Level Response

Expander output level (vertical axis) plotted against input level (horizontal axis) for a Threshold setting of -48dB, an Expansion Ratio of 4 and Soft Knee off (blue) and Soft Knee on (red). The black line is the unity gain Bypass response.

Threshold

Specifies the input signal level below which (assuming Soft Knee is disabled) gain reduction will occur in the Expander.