Shipping Of The Shruti-1 PCBs Will Start Shortly

If you plan to build a Shruti-1 synth you should hurry. Shipping seems to start very, very soon. BUT the PCBs and kits are limited only to a small amount.

Info via Mutable Instruments:

Old-school technology

Minimalist digital oscillators…

800MHz ARM core? Sharc DSP? Hardware-accelerated band-limited interpolation? Come on guys! The Shruti-1 runs on a modest AVR microcontroller (of the Arduino fame) clocked at 16 MHz and providing a whopping 2kb of RAM. You’re more likely to find this 8-bit wonder in vending machines than in synths… Yet, the Shruti-1’s firmware squeezes the most out of this tight processor to render classic waveforms, but also FM or weird digital sounds – all of them in their full 8-bit quirkiness.

... with an analog twist!

Today’s synths use DSPs or general purpose CPUs to emulate classic analog filters. To color and warm up your sounds, the Shruti-1 directly uses the real thing: a CEM3379 VCF/VCA, belonging to a lineage of chips found in the Prophet VS, my beloved Ensoniq ESQ-1 or the Waldorf Microwave. Perfect for fat basses or lively sequences.

DIY, Dudette!

The design is so simple you can build the Shruti-1 yourself. In fact, you’ll have to – the first units will be distributed as a kit. Hacking and experimenting with the Shruti-1 is easy – whether you want to connect an accelerometer or add a new synthesis algorithm to its OS.

Small and portable

It’s up to you to decide what kind of case you want to put the Shruti-1 internals in – but with a 10×7.5 cm main board, and a 10×6.5 cm controller board, this is certainly not going to be a 19” rack or a massive desktop module. Oh, and you can power it from a 9V battery.

No compromises

On musicality…

There are many cheap DIY noise-makers out there… but how many of them can you really compose melodies on, or use on stage to play sequences with? The Shruti-1 is by contrast a complete MIDI instrument. You can play it from a MIDI keyboard – the joys of weighted piano keys – or your favorite sequencer. As for the sound quality, we did our best to make it sound as little “cheap/chippy” as possible, and tried to cover a wide range of textures. Listen to some samples .

... and on features

Many features you expect to find on a professional synth – arpeggiator, patch memory, freely assignable modulations – are implemented. Some of the Shruti-1 features, like the step sequencer or the non-western tunings, are not even available on many synths manufactured nowadays. Have a look at the user manual to find out what’s there!


Digital/analog hybrid monosynth.

Digital oscillators

Available for all oscillators, and band-limited

impulse train (high-pass filtered square wave) with pulse-width modulation
square with pulse-width modulation
triangle with waveshapping
sawtooth with waveshapping
Available for oscillator 1 only

sawtooth with sweepable resonance (casio cz-like). This creates a resonance directly in the oscillator output, without using the filter
simplistic FM (1>2 configuration), with adjustable modulation index and frequency ratio
8bit-like harsh waveforms with wavetable scan
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
wavetable (16 waveforms) with wave morphing, for drones
“sweep” oscillator which scans through all the band-limited waveforms

adjustable oscillator balance
mixing algorithms: simple sum, simple sum with synchronization, ring modulator, xor modulator
extra sources: noise & sub-oscillator (triangle or square)

CEM3379 analog VCF/VCA, with external audio input

LFOs: 2, with square, sawtooth, triangle, sample & hold shapes. Syncable to tempo
envelopes 2 ADSR
modulation matrix: up to 14 source -> destination connections. Adjustable modulation amount in the -100% — 100% range
modulation sources:
LFO 1/2
step sequencer
arpeggiator gate
mod. wheel
pitch bender
DC offset
CV inputs 1/2/3
noise generator
ENV 1/2
note velocity
note number (eg for filter tracking)
keyboard gate
modulation destinations:
filter cutoff
VCA gain
pulse width/Parameter osc. 1/2
pitch osc. 1/2
vibrato (fine pitch, applied to osc 1 & 2 simultaneously)
oscillator balance
noise level
subosc level

step sequencer: 16-steps (4-bits value per step). Adjustable cycle length
arpeggiator: 15 rhythmic patterns, each of them with up/down/up&down/random variants. 1-4 octave range
clock: internal, 40-240 BPM with swing, or external (MIDI)
tuning: alternative tuning schemes/keyboard mappings: pythagorean scale, just temperament, 1/4 tone on E/A/B, Melakarta ragas
“patch performance”: custom page in which 4 user-selectable parameters can be assigned to the 4 editing pots
System and memory

MIDI implementation: notes, controllers, clock synchronization, patch editing by NRP, individual patch load/save by SysEx
patch memory: 16-patches stored in EEPROM
easter egg
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: 3 CV inputs (0-+5 V, labelled “HACK_ME!” on the PCB) for easy experimentation with controllers, accessible through pin header on the motherboard
MIDI: in, out (logical thru + patch dumps)
serial: tx/rx/reset pins for interfacing with an usb->serial chip, for on-chip firmware development
12 facade LEDs (current page / modulation matrix visualization)
backlit 2×16 LCD display
4 pots for patch editing
volume and input gain pot
5 navigation switches, one inc/dec switches pair


MidiVox: $26 Synthesizer Shield For Your Arduino

Via Narbotic Instruments:

MidiVox turns an Arduino board into a programmable MIDI synthesizer.

The assembled kit provides an isolated MIDI input jack along with a single-channel, 12-bit, digital audio output. Any MIDI keyboard with a DIN-5 output can be used to control the shield. Assignable knobs/faders on your controller will come in handy for modifying synth parameters as sou play.

Intended for use as an experimental digital synthesizer, the board can be easily modified for use as a MIDI->CV converter or a MIDI output device.

The kit incorporates an MCP4921 Digital to Analog Converter (DAC) chip, with an 6N138 optocoupler for industry-standard MIDI input.

Features include:

  • Indicator LEDs for power and MIDI data
  • 2-pole passive lowpass filter
  • Onboard volume trimmer w/ knob
  • Slide switch for allowing MIDI or Arduino programming data
  • Single channel 12-bit audio out
  • optocoupled MIDI input
  • a fine lookin’ PCB

[watch on youtube]