The C400 is a professional 4 channel compressor that can be operated as 4 separate processors or linked as two independant stereo pairs. In Link mode, Channel 1 and 3 provide Master control and 'rms summing' is used to ensure that signals from both the linked channels affect compression equally. Each channel has fully variable controls for Threshold, Ratio, Release and Gain. The compression slope can be switched between Hard or Soft knee, with Hard knee providing tight control of compression Ratio and Soft knee a more progressive style of compression. Two Attack/Release modes are available; Auto (program dependant) Attack/Release or Auto Attack with manuallly adjustable Release. A low frequency Program filter can be switched into the sidechain to reduce the effects of bass heavy material causing over compression. Each channel also has a sidechain insert jack. Gain Reduction is displayed on an 8 segment LED bargraph. The Bypass and Link switches also have led indicators. All Inputs and Outputs are electronically balanced and can be switched between +4dBu and -10dBV operating levels.