STEREO_AUDIO_COMPRESSOR

Published:2009/7/13 2:28:00 Author:May | From:SeekIC

The block diagram of the stereo compressor is shown. The input signal is fed to a voltage-con-trolled amplifier (VCA) that has a nominal gain of unity. Some of the output signal is fed to a precision rectifier followed by a logarithmic converter circuit. The output of this block is a dc voltage proportional to the log of the average level of the input signal. By sending some of this dc control voltage to the VCA, the gain of the VCA is automatically reduced when the input signal exceeds a user-determined threshold level. It is important to note that the signal level is determined after the VCA and not before. This allows the output level to increase and sound normal, but not increase as much as the input signal does. By varying the amount of feedback, the compression ratio is adjusted, which, in conjunction with the THRESHOLD control, determines the operating characteristics of the compressor. The optional sidechain jacks permit external processing of the audio signal or substitution of a completely different audio signal as the control signal. This add-on circuitry lets the user ex-periment and achieve some useful audio effects.



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