Jeannie 8 voice polyphonic DIY Synthesizer

Jeannie is an 8-voice polyphonic open source synthesizer with 24dB Ladder Filter and 12dB State Variable Multimode Filter

Jeannie is an 8-voice polyphonic open source synthesizer kit with digital sound synthesis and digital filters based on a fast ARM Cortex-M7 processor with 1MByte Ram. For sound generation, the user has a variety of classic and band-limited waveforms at his disposal. A pool of 15 waveform banks with 63 different waveforms each offer plenty of space for sound experiments. A waveshaper with different characteristics provides for gentle to vicious sounding distortions. To tame the waveforms, there is a digital 12dB multimode filter with fade function from low-pass to highpass and a band-pass function. In addition, there is a 24dB LP ladder filter. A 24Bit DSP effect module with adjustable parameters rounds off the sound synthesis. An integrated polyphonic 16-step sequencer provides for the playfulness of the small synthesizer. A total of 2048 sound patchesfrom 15 banks can be loaded and stored via an integrated SD card. A color 1.8 inch TFT display allows a clear menu structure and easy operation of the synthesizer. The parameters are entered via four rotary knobs below the display and an encoder for selecting the sound programmes and switching to the menu functions. In addition, there are six buttons for operating special synthesizer functions.

ā€¢ DIY 8-voice polyphonic synthesizer
ā€¢ ARM Cortex-M7 processor 720MHz with 1MByte Ram
ā€¢ two digital oscillators per voice
ā€¢ 15 waveform banks with a total of 945 waveforms
ā€¢ 12 standard waveforms, some of which are band-limited
ā€¢ Noise generator (white and pink noise)
ā€¢ Oscillator Modulation (XOR, XMOD, MOD, AND, PHA, FM)
ā€¢ Waveshaper with different curve shapes
ā€¢ 2 LFOs with 6 different waveforms and fade in / fade out function
ā€¢ 2 ADSR generators 0.3ms ā€“ 12s with positive and negative control
ā€¢ 1 PWM LFO from 0.04Hz - 25Hz
ā€¢ Digital 12dB multimode filter with resonance and fade function (LP/HP/BP)
ā€¢ Digital 24dB low pass ladder filter with resonance
ā€¢ 24Bit DSP effect module with 15 effects and adjustable parameters
ā€¢ Polyphonic 16 step sequencer
ā€¢ SD cards for loading and saving the sound programs max. 2048
ā€¢ Colored 1.8 inch display with a resolution of 160x128 pixels
ā€¢ Volume control
ā€¢ Boost function for improved bass reproduction
ā€¢ Stereo audio output jack 6.3mm
ā€¢ 4 potentiometers for parameter input
ā€¢ Encoder for menu control and sound selection
ā€¢ 6 function keys
ā€¢ Midi In and Midi Out / Midi True
ā€¢ USB 2.0 midi interface
ā€¢ Simple firmware update via USB
ā€¢ External power pack 12V DC / 1000mA
ā€¢ and power switch

Sounds on soundcloud ā€¦

Videos on youtube ā€¦


Panel Board


Teensy 4.1 MCU Board with 720MHz

32bit DAC Board PCM5102A

SPN1001-FV1 Effect Board


Greetings from germany. Rolf


My latest video Klang Impressionen

I personally like the sequence from 16:00 very much. All played live and randomly with the ARP in DeepMind 6. The high chirp tones are played by the DeepMind 6 and the others come from Jeannie.

Greetings Rolf


Hi Rolf,

Thanks for sharing this. Jeannie sounds great!

For a while I have been using Teensy 3 and 4 in MIDI controller projects, and have recently been thinking about adding a basic synth on board so that the controller can also stand alone as a musical instrument. So Iā€™m quite interested to see synth designs like yours which are based on Teensy. I previously experimented with the Teensy Audio Library and managed to get some nice sounds. On the base 600MHz Teensy 4.1 the Moog Ladder filter seemed to use quite a lot of CPU, with a couple of oscillators it was around 10% CPU if I recall correctly. Overclocking is obviously one way around this problem.

How do you find the performance of the Moog Ladder versus the State Variable filter?

I notice that you used an external effects DSP. Is this purely for performance reasons, or is there some other advantage of the SPIN-FV1 over software effects running on the Teensy?

Cheers, Stewart

Hello Stewart. Thank you for your interest. In the Jeannie I have integrated both filter types. In the System menu you can select Ladder or State Variable Filter. The CPU performance with 8 voices is between 65-75% depending on the sound patch. The memory utilization is around 85%.
Additional audio effects would overload the Teensy 4.1 processor. For this reason we used an external effect DSP (Spin Semiconductor FV-1). This DSP offers up to 15 programmable effects.

Jeannie voice

At the moment we are still working on a modulation extension with a 3rd LFO.

Here are some sound samples

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