First glimpse of the Mutable Instruments ShrutHI-1 digital/analog hybrid monosynth

September 13, 2010 · Posted in Uncategorized 

A sneak preview of a new DIY synth project – the Mutable Instruments ShrutHI-1 digital/analog hybrid monosynth.

The video demonstrates some of the presets on ShrutHi-1 Kit #000.

Specs below. See the Mutable Instruments site for details.

2 digital oscillators

  • band-limited sawtooth with adjustable phase
  • band-limited square wave with adjustable pulse-width
  • band-limited triangle wave with adjustable waveshapping
  • phase-distortion emulation of a low-pass filtered sawtooth (casio CZ-101)
  • phase-distortion emulation of a low-pass filtered sawtooth with high resonance (casio CZ-101)
  • phase-distortion emulation of a low-pass filtered sawtooth in the Rocker Launcher’s world in which sine waves are turned into triangles (casio CZ-101)
  • mysterious phase-distortion thing (could have been in the CZ-101 if the engineers at casio dared…)
  • phase-distortion emulation of a Jew’s harp / Morsing (could have been in the casio CZ-101)
  • stack of 4 detuned sawtooth waves (with aliasing)
  • simplistic FM (1>2 configuration), with adjustable modulation index and frequency ratio
  • wavetables, wavetables, wavetables!
    • sweepable table of basic waveforms
    • tampura transwave
    • PPG harsh creature
    • single cycle waveforms taken from D50 patches
    • cello transwave
    • slap bass transwave
    • organ/drawbars single cycle waveforms
    • male voice
    • user wavetable, can be edited by SysEx messages
  • 8bit-like harsh waveforms with wavetable scan
  • sine wave with variable amount of bitcrushing
  • poor man’s square with pulse-width modulation (plenty of aliasing but fat for basses)
  • colored noise (sweep from low-pass filtered white noise -> white noise -> high-pass filtered white noise)
  • lo-fi vowel synthesis (think “speak and spell”) with vowel morphing


  • adjustable oscillator balance
  • mixing algorithms: simple sum, simple sum with synchronization, ring modulator, xor modulator, sum with post-mixing tanh fuzz
  • extra sources: noise, sub-oscillator (triangle or square) or percussive attack generator (click, glitch, blow, metallic, pop)

Audio quality/resolution

  • Internal digital audio signal processing chain: 39062 Hz, 8 bits.
  • Internal digital control signals processing chain: 976 Hz, 8 bits.
  • Digital outputs: 10 MHz, 1 bit.


  • Exchangeable analog signal processing boards:
    • CEM3379: based on the CEM3379, uses the same circuit as the original Shruti-1 with the “click filtering” mod
    • SMR4: a 4-pole LPF (very SSM2044-like) and linear VCA built with the widely available LM13700 transconductance amplifier and TL074 op-amp
    • SSM2044: SSM2044 4-pole LPF, SSM2164 2-poles HPF + linear VCA.
    • (à suivre)


  • LFOs: 2, with square, sawtooth, triangle, sample & hold, and step sequencer shapes. Syncable to tempo. Adjustable “raise/attack” time. LFOs can be free-running, sync’ed to envelope retriggers, or retrigger envelopes.
  • envelopes 2 ADSR
  • modulation matrix: up to 12 source -> destination connections. Adjustable modulation amount in the -100% — 100% range
  • modulation sources:
    • LFO 1/2
    • step sequencer
    • first / second half of the step sequence
    • arpeggiator gate
    • mod. wheel
    • aftertouch
    • pitch bender
    • DC offset
    • CV inputs 1/2/3/4
    • MIDI CC 16 to 19
    • noise generator
    • env 1/2
    • random value resampled at each note on
    • note velocity
    • note number (eg for filter tracking)
    • keyboard gate
    • audio signal from the mixer output (decimated at 1kHz)
  • modulation destinations:
    • filter cutoff
    • VCA gain
    • pulse width/Parameter osc. 1/2
    • wide pitch osc. 1/2
    • pitch, applied to osc 1 & 2 simultaneously
    • very fine pitch, applied to osc 1 & 2 simultaneously
    • oscillator balance
    • noise level
    • subosc level
    • resonance
    • PWM CV output 1
    • PWM CV output 2
    • 2 bits digital value on CV output 1/2
    • LFO1 FM
    • LFO2 FM


Clock/tempo generator

  • internal clock: 40-240 BPM, with some additional extra fast tempi for effects (270, 300, 360, 480, 600, 720, 960)
  • external MIDI clock with divider
  • 6 groove templates (swing, shuffle, push, lag, human, monkey) with adjustable amount


  • 1-4 octave range
  • up, down, up&down, random
  • 15 preset rhythmic patterns + 1 programmable rhythmic pattern
  • warp: creates complex rhythms by cyclical repetitions of steps (eg 1212343456567878 instead of 12345678)
  • latch/hold


  • 16 steps, with legato/slide, velocity, and modulation
  • 4 modes corresponding to different interactions between the sequence and keyboard play: latch / transpose / loop recorder / override


  • custom page in which 4 user-selectable parameters can be assigned to the 4 editing pots
  • microtunings/key maps for arabic scales (1/4 tones) and a selection of hindustani ragas
  • portamento, legato on/off
  • master tune

System and memory

  • complete MIDI implementation, including patch editing by CC or NRPNs, patch and sequencer data transfer, full memory backup, wavetable transfer
  • MIDI out modes: off, thru, thru+knob movements sent as CC, sequencer/arpeggiator generated events only, polychaining, split (plays notes below split point, forwards the other notes)
  • patch memory: 80 patches and 80 sequences stored in EEPROM (no backup battery required)
  • firmware update by SysEx

Hardware and connectors

  • power: 2.1mm connector, requires 7.5V-9V 300mA supply (can be unregulated). Center pin positive (+), outer collar negative (-)
  • audio input/output: 6.35 Jack (Mono audio out), 6.35 Jack (External signal in)
  • cv inputs: up to 4 CV inputs for easy experimentation with controllers ( might not be broken out on analog VCF/VCA board )
  • cv outputs: up to 2 CV outputs ( might not be broken out on analog VCF/VCA board )
  • MIDI: in, out
  • serial: extra UART TX pin available on control panel board (might be used in future firmware updates to control extension boards)
  • ISP connector for firmware development
  • controllers:
    • 8 facade LEDs (current page / modulation matrix visualization)
    • 6 navigation switches
    • 4 pots for patch editing
    • clickable rotary encoder for fine parameter adjustment or navigationbacklit 2×16 LCD display


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