The  SB4001 500 Series Stereo Bus Compressor from Serpent Audio is a quad VCA based compressor, and can be used for either stereo or mono applications. It can be used for gain reduction and is suitable for a number of signal types and musical applications.
 
This stereo compressor has six Ratios, ten Attack Times, High Pass/Boost/Slope Sidechain Filters, Wet/Dry Blend Control, External (Key) Input, Classic Stepped Release Settings, Classic and Alternate Auto Release, Variable Release Control, and "Grind" Mode (a valve style harmonic drive adding vintage color).