ElectroTechnique TSynth An $99 Open Hardware Synthesizer

ElectroTechnique shared this intro video for the TSynth, a low-cost DIY desktop synthesizer, based on the PJRC Teensy 4.1 micro-controller board.

The virtual analog synth is 12-voice polyphonic, with two oscillators per voice.

The pcb and front panel are available from Tindie.com with SMD 4067 multiplexers, 6N138 opto-isolator, capacitors and resistors fitted. ElectroTechnique says that the entire cost of parts to build TSynth will be around $99, if you buy components from the cheaper suppliers, and the build time should take about two hours.

Plans for a 3D printed/laser cut enclosure are also available.



  • 12 voice polyphony (last note priority), two oscillators per voice, velocity sensitive, detunable with +/- 2 octaves range, Sine/Sample & Hold (like tuned noise)/Square/Sawtooth/Ramp/PWM/Var Triangle/User waveforms and level. Square, Sawtooth and Pulse waves are band-limited.
  • Pulse Width/Var Triangle can be set for each oscillator with PWM by dedicated LFO or from the filter envelope
  • Pink or white noise level
  • Dedicated LFO for pitch mod (can be retriggered by note on), Sine/Triangle/Sawtooth/Ramp/Square/S&H waveforms
  • Pitch can be modulated by filter envelope (+/-)
  • Oscillator FX – XOR creates lots of harmonics with certain waveforms and X Mod ‘Cross Modulation’ bell-like sounds.
  • Dynamic Unison with all 24 oscillators detunable from each other – one, two, three or four notes can be played with oscillators distributed among them
  • Chord Unison with all oscillators playing a chord selected from detune control – major, minor, diminshed…
  • Polyphonic Glide with variable time


  • State variable 12dB filter (SVF) with continuous mix between LP and HP (provides notch filter) and BP
  • Cutoff freq and resonance
  • Cutoff can be modulated by dedicated ADSR envelope (+/-), dedicated LFO
  • LFO has same waveforms as pitch LFO (can be retriggered by note on) and rate can be set to match MIDI clock (tempo) with variable time division (1,3/4,1/2,1/4,1/8…)


  • Dedicated ADSR envelope
  • Volume
  • Effect amount and mix – currently for stereo ensemble chorus rate and mix but could be set up to allow choices in Settings menu

Patch & Program Buttons

  • Encoder with button for data entry, Back button for menu navigation
  • Save and Delete buttons for storing patches
  • Holding Settings initialises the current patch to match the panel controls. Holding the Save button takes you into a patch deletion page.
  • Settings Menu – Velocity curve, Pitch Bend and Mod Wheel range, VU Meter, Oscilloscope display, Bass enhance, MIDI In and Out channel.


  • USB HOST MIDI Class Compliant (direct connection to MIDI controller, no PC needed)
  • USB Client MIDI In from PC
  • MIDI In 5 pin DIN
  • MIDI Thru 5 pin DIN


  • SGTL5000 Audio Shield 16 bit, 44.1 kHz Stereo out
  • USB Audio in/out—appears as 16 bit, 44.1 kHz audio interface on PC

See the ElectroTechnique site for details.

25 thoughts on “ElectroTechnique TSynth An $99 Open Hardware Synthesizer

  1. Nicely thought out, with a creditable sound to offer. I like the more colorful GUIs of name synths, but I’m for sure impressed by smaller efforts that still have some reach. A perfect panel-buddy for one of those more famous red synths.:P

    1. Did you come here only to spam about Behringer garbage?

      You’re asking about the price under the headline ‘ElectroTechnique TSynth An $99 Open Hardware Synthesizer’.

      The TSynth has the same polyphony as Behringer’s only polyphonic synth, but costs $800 less.

      For the record, the Behringer 2600, like their miniature Arp 2500 knockoffs, is a small, sad imitation of the real thing.

      1. No it’s not. Deep Mind has
        1. Filter per voice
        2. Effects processor
        3. Mod matrix including effects
        4. Keyboard

        DM is in different league, but I like open hw and tinsy as general idea.

      2. I agreed with you … until your last 2 statements. How can you possibly compare a DIY synth without housing or keyboard, to an $800 synth with a 49-key aftertouch keyboard, LCD screen, FX, pitch and mod wheels, software? And then you complain that the 2600/2500 is a sad imitation of the real thing. You complain about someone spamming their love for Behringer, which kinda makes you a spammer of Behringer hate. I agree it was a silly question given that the price (albeit estimated) is listed in the title.

        What do you think a teensy-powered synth is an imitation of?

      1. And the article says pretty clearly “ElectroTechnique says that the entire cost of parts to build TSynth will be around $99”.

        TimS’s comment just sounds like he came to the site to spam about Behringer synths, rather than to read the article and actually say something relevant about this synth.

  2. This is a brilliant idea and it’s fantastic that it’s open source and the price can be kept so low. It would be great to see some other derivatives of this too with different synthesis engines.

  3. As an open source DIY offering I like this and am on the waiting list for PCB and kit. AT present the PCBs go within minutes from the Tindie store which the developer uses as an outlet. The Architecture is quite malleable ,so I can see many DIY folks particularly those who have invested in making Eurorack modules being interested .
    Personally I hope someone from THONK in the uk, gets in contact with the developer and helps making this available . At present the PCBs etc get sold instantly .

  4. I cannot see any info re. MIDI CC implementation, other than it sends CC data as the knobs are turned.

    I hope that it can receive MIDI CC messages to control the many synth variables, like the Audiothingies- Micromonsta.

    What would make this product a lot cheaper – eliminate the entire control surface (except for maybe the display and patch select buttons) and only include the Teensy brain + the DAC board.
    – Then to control it all via MIDI CC’s from either a PC or tablet controller eg. CTRLR or a VST panel layout.

    1. as far as I can tell you’re free to edit it if the Midi implementation isn’t what you want, and also to release it in a different form factor. (Personally I’m not sure the appeal would be there for a knob-less version, because you may as well just use a VST or ipad synth if you’re using a computer or ipad to control it already.)

  5. Hello, thanks for the feature again. I’ve had lots of interest since May and have been getting the Teensy 4.1 version finished. All the information you’re looking for is on the website or in the User Manual and Build Guide, or you can email me.
    I’m looking for resellers to help with distribution as I’m limited in what I can do at the moment. I’m still excited each time I switch it on, after many months.
    The T4.1 is very capable and you’ll find TSynth has features rivaling what you may or may not find on desktop units costing ten times more. The important waveforms are band-limited now and I’m hoping people will have a go at the open source firmware code (basically Arduino level) and improve the sound further.

    1. Yeah. I am looking forward to finishing my build, but it was closer to $300 by the time I got all my parts. There’s a company in Brooklyn selling kits for about $275 and honestly it’s not a bad deal.

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