Sisyphus is built around a granular engine and a palette of eight new filters. Its granular system allows multiple grains to coexist within a single stereo audio stream, where they combine and interact with each other.

This filter is based on a comprehensive granular approach to sound: rather than a granular engine followed by a filter, it offers true integration of filtering into the grain-generation process. Each generated grain carries the filtering characteristics defined by the musician and will be combined with other grains according to evolving, configurable patterns.

These filters have been developed entirely from scratch in-house, without using typical filter libraries, so they each have their own unique color for you to explore!

Filters

Lowpass
Attenuates high frequencies above the cutoff frequency. 12 dB/oct slope.

Highpass
Attenuates low frequencies below the cutoff frequency. 12 dB/oct slope.

Bandpass
Lets through a band of frequencies around the cutoff frequency. 12 dB/oct slope.

Notch
Dips around the cutoff frequency while letting the rest of the spectrum pass through.

Peak 
Boosts the band around the cutoff frequency while allowing the rest of the spectrum to pass without a drastic cut.

Comb
Creates a series of cancellations and resonances based on an internal delay and feedback.

Karplus (Karplus-Strong)
Simulates the vibration of a string or looping resonance by combining a short delay, feedback, and damping.

Ladder
Inspired by Moog-style analog filters, with four stages in cascade. Features a steep slope (24 dB/oct) and a distinctive resonance that can reach self-oscillation.

Filter Controls

Cutoff (Cutoff Frequency)
Defines the filter’s cutoff frequency or center frequency (depending on filter type), ranging from 10 Hz to 20 kHz.

Resonance
Emphasizes frequencies near the cutoff frequency, from a slight bump up to the edge of self-oscillation.

Feedback
Re-injects part of the output back into the filter input.

Variations
Introduces an instability in the setting of the cutoff frequency, resonance, or feedback (depending on the selected filter), allowing for a more or less “organic” filter character.

Grain Controls

The incoming sound is continuously sampled and segmented into buffers. Each segment is analyzed, filtered, and then extracted to become a grain. You can change the length of each grain, the interval between grains, the way grains follow one another, how they are arranged in relation to each other, and their density (number and influence).

Grain Length
Adjusts the length of the audio grains. The shorter the grains, the more the sound fragments into a “grained” granular texture; the longer the grains, the closer the result is to the original sound, but filtered and delayed. When multiple grains are played simultaneously, longer grains make echo effects more noticeable.

Grain Interval
Determines the time between the start of two successive grains (or the probability of automatic triggering).

Pattern
Grains are organized according to predefined, adjustable patterns. Several scenarios allow you to explore different ways grains can combine, from highly organized to more chaotic.

Density
Determines how many grains are played simultaneously and their intensity.

Variability
Sets the magnitude of the special effects specific to each pattern.

Transition
Defines the shape of the envelope applied to the grains as they link together.

Input and Output

Sisyphus works with two parallel channels that share the same settings. You can use it either in stereo mode or as two separate mono audio channels.

CV Inputs

Four CV inputs allow control of Sisyphus using other Eurorack modules. These inputs accept the standard Eurorack voltages (0 to 8 V).
The four basic parameters that can be controlled via CV are: Grain Length, Density, Cutoff, and Resonance.
However, you can configure the module differently using an external file on an SD card. In that case, any CV input can be assigned to any control, the input voltage range (from 1 to 8 V) can be set, LED brightness can be adjusted, and more.

Specifications

Width: 24 HP
Power Consumption:
+12 V: 200 mA
–12 V: 10 mA
+5 V: 0 mA
Depth: 28 mm

Carefully built in France, with all potentiometers bolted to the front panel, and shipped in a metal storage box.

Power cable and knurlies included.

Thanks Yi Jil for first test, music and video!

block diagram

What's New in Version 1.43:

– Grains can now be longer: up to 3 seconds per grain.
– The possible interval between two grains has been doubled.
– There are fewer auto-oscillation “accidents.” However, it's still possible to induce auto-oscillation with certain filters.
– Setting the Density knob to 0 allows you to hear the sound just before it enters the filter: this sound is then used by the granular engine and filtering processes.
– With the Comb filter, the Cutoff knob now allows exploration of the filter’s unique resonances, while the Variation knob accentuates filter distortions.
– The pattern effects have been emphasized, exerting greater influence on the cutoff frequencies per grain.