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.
The z2040’s sound spectra is wide and will excel over other filter types at creating bass lines, percussive elements, pads and drones. the three different regions of the gain knob allow for a variety of tonal options. first, a reproduction of the ssm2040 ‘sweet’ sound appears from min to 0db. a gain compensated resonance to add punch appears just at 0db and a soft and hard clipping, as well as very high gain output appears at just beyond 0db to max.
The z2040’s four modulation inputs are built to handle cv and audio signals, enabling deep modulation of the filter core and passing signals. a vc resonance input is provided to modulate and even clip the sine wave produced by the filter feedback loop. A frequency modulation input (fm) provides for dynamic filter sweeps and the unique vc-fm index provides modulation of the incoming fm signals. on top of that, the z2040 provides an audio vca that can be configured to act upon the input or the output of the filter.
The z2040 uses a space saver design but will produce a 'big' sound.