Synthino XM is a 5-note polyphonic MIDI synthesizer

This MIDI synthesizer is ideal for any musician or Maker looking to create some grooves.

In collaboration with Alex Dyba of GetLoFi, Nootropic Design founder Michael Krumpus recently debuted the Synthino XM, a five-note polyphonic synthesizer packed with a four-track sequencer running on the versatile ATxmega128A4U MCUSuccessfully funded on Kickstarter where it garnered just over $17,000, the open-source device boasts a fun, aesthetically-pleasing interface with just enough buttons and knobs to let users change parameters on-the-fly.


The gadget is equipped with a 1/4” output jack that not only works with headphones, but serves as a line output for recording and a direct connection to any guitar amplifier. With its standard five-pin MIDI input jack, both musicians and hobbyists alike can easily plug-in any MIDI keyboard, sequencer or drum machine to control the Synthino XM. Arguably one of, if not, the most exciting features has to be its integration of MIDI over mini-USB, which enables any model device with MIDI or DAW software to immediately recognize Synthino XM as an available output. The synthesizer can be used standalone as well, with just a 9V battery and a pair of headphones.


Synthino XM has three modes: synthesizer, arpeggiator, and groovebox. Synthesizer mode permits users to play the Synthino XM with a MIDI controller connected to the MIDI jack or from their favorite DAW software over USB. The arpeggiator allows users to play predefined arpeggios or set their own arpeggio notes with MIDI. Meanwhile, groovebox mode is a bit more sophisticated with a “live” 16-step sequencer that lets musicians lay down four different tracks through a MIDI controller.


Visual indicators are in the form of four bright orange LEDs that can be found beneath each button. When powered on, a series of blinking LEDs prompt users to select a mode by pressing one of the buttons, numerically denoted by “1-3,” respectively. In certain modes, the pots have secondary functions labeled as “fn:” These functions are activated by simply hitting the “4” button, which if held down for three seconds can also reset the program and let users choose a new mode.

To round out its sleek design, all of the electronics are housed between a two laser-cut frosted acrylic layers. Other notable features include:

  • 5-note polyphony for superb playability
  • 12 waveforms, 4 drum samples
  • 12-bit audio at 25KHz output rate
  • 4 MIDI channels, each with separate waveform and ADSR envelope settings
  • Low pass filter with cutoff frequency and resonance controls
  • 2 independent low frequency oscillators (LFOs): pitch and filter
  • Selectable waveform for LFOs
  • 1V p-p audio output voltage with enough current to drive headphones
  • Arpeggiator mode, up to 16 notes
  • 4 arpeggiator patterns: up, down, up-down, random
  • 4 built-in arpeggiator chords or use MIDI to specify up to 16 notes
  • Arpeggiator pitch transposition control
  • Tempo control with MIDI clock input
  • 16-step live performance “groovebox” sequencer
  • Pitch fine-tuning adjustment
  • Programmable/upgradable over USB


The Synthino project was first conceived back in 2014. However at the time, it was limited by only five buttons and three pots with no way of playing notes, and like any other prototype, it wasn’t too visually appealing either. Beyond that, the aptly named Synthino ONE was built around an ATmega328 MCU. According to the Krumpus, the latest iteration of the instrument called for a faster processor with double the speed and four times the memory. And so, the ATxmega128A4U was chosen.

2 thoughts on “Synthino XM is a 5-note polyphonic MIDI synthesizer

  1. Pingback: Audiomáquinas | Synthino XM: Un sintetizador MIDI polifónico de 5 notas

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