Compressors are a key tool in audio mixing, and they are used to reduce the dynamic range of an audio signal. This means that they reduce the difference between the loudest and softest parts of the signal, allowing the overall level to be increased without clipping or distortion. Compressors work by applying a variable gain reduction to the signal, based on the input level and the settings of the compressor.
When a compressor is applied to an audio signal, it first detects the level of the signal. This is typically done using a detector circuit, which measures the amplitude of the signal and generates a control voltage (CV) based on the level. The CV is then used to control the gain reduction applied to the signal.
The amount of gain reduction applied by the compressor is determined by several factors, including the threshold, ratio, attack, and release settings. The threshold is the level at which the compressor starts to reduce the gain of the signal. When the input level exceeds the threshold, the compressor starts to apply gain reduction. The ratio is the amount of gain reduction applied for each dB that the input level exceeds the threshold. For example, a ratio of 4:1 means that for every 4 dB that the input level exceeds the threshold, the gain is reduced by 1 dB.