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.
