Quad channel compressor with unique and intuitive presence control that improves the high frequency sound quality without increasing noise or squealing (howl-round). Originally devised to reduce the dynamic range of audio signals. To do this they use gain modification that makes adjustments to signal levels automatically, dependant on the level and dynamic of the signal itself and upon the character and control settings of the particular compressor unit. Throughout the history of dynamics processing many different types of compressor have been produced using many different types of gain technology. Each type has a distinctive sound. Users have found many applications which benefit from these often unintentional compression audio artifacts, taking the use of compressors far beyond simple dynamic range reduction, sometimes even generating the complete reverse; dynamic enhancement. It is with these creative applications in mind, that the DN540 has been designed to offer a latency-free, comprehensive and compact dynamics processing package.