Building off of the very popular SB4000 DIY Compressor, the SB4001 pushes the limits and sets new standards for the 500 Series Format. Boasting Quad VCA's, 6 ratio's, 10 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, as well as "Grind" Mode (a proprietary valve style harmonic drive adding vintage color), the SB4001 is capable of delivering whatever sound you need. Whether Clean, Dirty, Vintage, Subtle, or Crushed, the SB4001 is sure to be one of the most flexible compressors in your arsenal.