The Z2040 is a powerful 4-pole low pass filter with a similar core to that of the SSM2040 filter chip used in the Prophet 5 REV2 synthesizer. both the Z2040 discrete circuit and the SSM2040 integrated circuit are based on a us patent assigned to Oberheim Electronics in the 70s.
However, the Z2040 includes additional circuitry to provide even more modulation capabilities not originally found in the SSM2040, extending its unique sound signature.