Mutable Instruments Shruthi 1 Synthesizer

via this auction

via the seller:
"I professionally built this myself and it has a rare and nice looking black on white display. It does not include a case, but I never used one with it. Has never been gigged, only played a couple times. It has the SMR4 filter installed, which sounds a lot like the SSM2044 (korg polysix etc). Real smooth and sweet with a good amount of resonance!"

Full specs:
Digital/analog hybrid monosynth.
2 digital oscillators

band-limited sawtooth with adjustable phase
band-limited square wave with adjustable pulse-width
band-limited triangle wave with adjustable waveshaping
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
harsh, aliasing-full waveforms obtained by bit-toggling
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



Mixer

adjustable oscillator balance
mixing algorithms: simple sum, simple sum with synchronization, ring modulator, xor modulator, sum with post-mixing tanh fuzz, mixing with sample rate reduction.
extra sources: noise, sub-oscillator (triangle, square, pulse, -1 or -2 octaves) 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.

Filter

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.
IR3109: Classic Roland filter + LM13700 linear VCA.
(à suivre)

Modulation

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)
operations (sum, product, max, min…) between modulation sources
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
Envelopes attack speed
LFO1 FM
LFO2 FM

Performance
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

Arpeggiator

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

Sequencer

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

Performance

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. See the standard MIDI implementation chart here.
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. Warning: only use a signal in the 0-5V range. Deeper or high peaks in the signals might damage the Shruthi-1’s ADC.
cv outputs: up to 2 CV outputs.
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 navigation
backlit 2x16 LCD display"