8-4

Compressor

Figure 8-2Compressor component.

A compressor (see Figure 8-2) is used in situations where the input signal has a greater dynamic range, or ratio of loudest to softest, than is desired in the output signal. Compression is accomplished by preventing the output signal from changing in level as much as the input signal, and can be thought of as a form of automatic gain riding.

Familiar Controls

Most of the controls in the ISP-100 Compressor are common to nearly all traditional dynamic range compressors. These controls should be familiar to anyone with experience in the operation of any compressor.

Compression Ratio

The Compression Ratio control adjusts the amount by which the output signal level changes for a given change in input signal level. When compressing, the output level change in dB will be equal to the input level change in dB divided by the compression ratio:

output level change

= input level change

compression ratio

For example, if the compression ratio is 2:1 and the input level changes by +10 dB, then:

output level change =

input level change

= + 10 dB = +5 dB

 

compression ratio

2

Any compressor is essentially a limiter once the compression ratio is increased beyond approximately 6:1.

Compression Ratio is selectable from {1.2:1, 1.5:1, 2:1, 3:1, 4:1, 6:1, 8:1, 12:1, 16:1, 24:1}, though any compressor is essentially a limiter once the compression ratio is increased beyond approximately 6:1.

Threshold

The Threshold control adjusts the input signal level above which compression is used. When the input signal level is below the

10 July 1998

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Telex ISP-100 manual Compressor, Familiar Controls, Compression Ratio, Threshold