Purple Audio BIZ: Add some great color to your 500 rack, both literally and figuratively. The discrete 3-amplifier BIZ sounds truly unique. With separate input gain and output level, along with a dual mode that splits the signal between a pair of Class-A op-amps, the BIZ is capable of an incredibly wide-range of tone – and it delivers an awesome 75db of clean gain! The BIZ is truly hot. Hot, and purple.