The ST-CL2 is a high performance compressor/limiter designed to maintain a constant average output level and effective peak control over a wide range of input levels. The input and output are line level and each may be wired balanced or unbalanced. Trimmers provide adjustment for all usual professional and consumer audio input and output levels. Internal detectors feed three timing circuits. The threshold level and slope of each timing circuit are incremented to respond sequentially to signals of varying amplitude and energy levels. The ST-CL2 features a soft-knee compression threshold and compression ratio which automatically adjust to the program material. Two LED indicators cover the incremental ranges of compression, making setting of the input level quick and easy. Two ST-CL2s may be strapped together for stereo operation by connecting the coupling terminals between the two modules.