rossum-electro-music-evolution

Rossum Electro-Music Evolution

Legendary ladder filter with voltage-controlled pole count and character

16 HP Eurorack module

Evolution is a pure analog voltage-controlled lowpass ladder filter based on Dave Rossum's legendary E-mu Systems 2100 LPF, offering variable pole count (3-6 poles), voltage-controlled distortion character via the Species control, and voltage-controlled resonance with Q Level Compensation. Its ability to sweep pole count in real time — including at audio rates — produces entirely unique timbral transformations unavailable in traditional ladder filters.

Features

  • Pure analog ladder filter based on E-mu Systems 2100 LPF / 1100 submodule design by Dave Rossum
  • Voltage-controlled pole count: 3, 4, 5, or 6 poles (18, 24, 30, 36 dB/oct) with continuous transitions
  • Real-time pole modulation at LFO and audio rates for unique timbral effects
  • Species control: voltage-controlled drive level into ladder for variable characteristic distortion
  • Q Level Compensation control: variable boost of sub-cutoff frequencies to counteract resonance-induced thinning
  • Voltage-controlled resonance (Q) using SSM2164 VCA cells
  • Self-oscillation mode producing high-quality sine wave for use as VCO
  • 1V/Oct frequency tracking accurate over 10 octave range, rivaling best analog VCOs
  • Frequency range: 22Hz to 22kHz (manual); 0.02Hz to 40kHz (with CV)
  • Three frequency CV inputs: 1V/OCT (full level), FREQ CV2 (attenuverter), FREQ CV3 (attenuator)
  • DC coupled throughout — can process CVs as well as audio
  • Input: up to 20Vp-p; Output: up to 20Vp-p without clipping

Controls & Jacks (25)

  • 1V/OCT— Calibrated 1V/Octave frequency control input with accurate 10-octave tracking. Also functions as high-quality sine wave oscillator when in s
  • Q CV2— Attenuverter for Q CV2 input, allowing positive and inverted resonance modulation.
  • SPECIES CV1— Full-level distortion control voltage input. Summed with SPECIES knob and SPECIES CV2 input.
  • Q— Sets the initial height of the resonant peak. At approximately 4V, the filter enters self-oscillation mode producing a pure sine wave.
  • Q LEVEL COMPENSATION— Controls the balance between resonant signal and frequencies below cutoff. Fully counterclockwise gives traditional ladder behavior; clockwi
  • GENUS— Sets the initial number of filter poles (3, 4, 5, or 6), which defines the attenuation slope. 5 volts covers the entire pole range.
  • SPECIES— Controls the signal level into the ladder's distortion circuitry, from subtle distortion (full counterclockwise to 12:00) to pronounced dist
  • Q CV1— Full-level resonance control voltage input. Summed with Q knob and Q CV2 input.
  • FREQ CV2— Attenuator for FREQ CV3 input, controlling frequency modulation at 1V/Oct response.
  • FREQ CV2— Frequency control voltage input (modulated by FREQ CV2 attenuverter knob). Summed with FREQUENCY knob and other CV inputs.
  • GENUS CV2— Attenuverter for GENUS CV2 input, allowing positive and inverted pole count modulation.
  • GENUS CV2— Full-level pole count control voltage input. Summed with GENUS knob and GENUS CV2 input.
  • FREQ CV3— Attenuverter for FREQ CV2 input, allowing positive and inverted frequency modulation at nominal 1V/Oct response.
  • OUTPUT— Filtered audio output. Provides signal levels up to 20Vp-p without clipping, depending on input level and control settings.
  • GENUS CV1— Pole count control voltage input (modulated by GENUS CV2 attenuverter knob). Summed with GENUS knob and GENUS CV1 input.
  • SPECIES CV2— Attenuverter for SPECIES CV2 input, allowing positive and inverted distortion modulation.
  • SPECIES CV2— Distortion control voltage input (modulated by SPECIES CV2 attenuverter knob). Summed with SPECIES knob and SPECIES CV1 input.
  • Q CV2— Resonance control voltage input (modulated by Q CV2 attenuverter knob). Summed with Q knob and Q CV1 input.
  • INPUT— Main audio input. Accepts signals up to 20Vp-p. DC-coupled, so CVs can also be processed.
  • FREQ CV3— Frequency control voltage input (modulated by FREQ CV3 attenuator knob). Summed with FREQUENCY knob and other CV inputs.
  • FREQUENCY— Sets the initial cutoff frequency from approximately 22Hz to 22kHz (without CVs). With CVs, range extends from 0.02Hz to 40kHz.
  • 3 POLES— Indicator showing when 3-pole setting is active.
  • 4 POLES— Indicator showing when 4-pole setting is active.
  • 5 POLES— Indicator showing when 5-pole setting is active.
  • 6 POLES— Indicator showing when 6-pole setting is active.

How-To Guides

  • Classic Moog-Style Lowpass
  • Precision Sine Wave VCO
  • Bubbly Pole Modulation
  • Audio-Rate Pole FM
  • Fat Bass with Q Compensation
  • Species Distortion Sweep
  • Self-Oscillation Arpeggiator via Genus
  • Species AM Oscillator
  • 18dB Soft Warmth (3-Pole Mode)
  • 36dB Brutal Darkening (6-Pole Mode)

Explore the interactive Evolution panel on BleepDex — tap any control to learn what it does.

8c571ce