SUNLESS CITY III / VI POLE CASCADE FILTER is an exceptional transistor-based cascade ladder low-pass filter, built on a unique six-pole design. The module attenuates frequencies above the fixed control voltage cutoff point at a rate of 36 dB per octave and 18 dB per octave. The respective six-pole and three-pole ladder positions can be selected via the ‘Slope Type’ slide switch.

The VCF’s signal input can be attenuated using the Drive Level control. Increasing this controller towards maximum level can produce gently overdriven sonic characteristics.

The module creates widely varying timbres utilizing classic subtractive synthesis techniques. The design features a robust exponential current converter and temperature compensation circuit, thereby producing precise voltage tracking.

The principal low-pass frequency is determined by the combination of the Cutoff Frequency position and the control input signals—the latter of which are denoted as F.M. I and F.M. II. Thus, SUNLESS CITY features two distinct and variable frequency modulators. The first potentiometer—denoted as ‘F.M. I’—serves as the frequency modulating tracking attenuator—with its maximum level corresponding to 1 volt per octave. The second potentiometer—denoted as ‘F.M. II’—serves as a precision attenuverter to attain bipolar exponential modulation of the filter’s cutoff amount.

The filter’s cutoff ranges from 10 Hz to 35 KHz.

The Regeneration control varies the filter’s resonance. Increasing this parameter will narrow and boost the strength of the cutoff peak, while simultaneously decrease the amplitude of the lower frequencies. The Q. level can be modulated via the dedicated Regeneration C.V. input.

At relatively high resonance settings, varying the control input voltages will emphasize the upper harmonics of the sound—to the point of selecting pitches in counterpoint to the movement of the signal frequency itself.

Significantly increasing the Regeneration level will lead to uninhibited self-oscillation, wherein the oscillation will permeate well over the totality of the audio bandwidth. This regeneration event results in forming a ‘clean’ sine waveform, which can be further utilized for ‘ping’ filtering, and for generating highly dynamic percussive patterns. The resulting sine wave is highly stable—and superbly tracks at 1 volt per octave.

The module’s Regeneration section has been intricately designed with specialized Q. compensation sub-circuitry—to automatically adjust for gain levels at higher Regeneration settings.

Specifications:

Model: EM-402

SKU: 424-402

Edition II

Dimensions: 12 HP (3U)

Power: +/- 12 V | 70 mA