- Only an STM32 evaluation board, 2 oscillators and some knobs and switches needed.
- Excellent audio quality: 16/24bit audio DAC with headphone amplifier
- Can load waveforms with Theremin sound directly from an USB stick
- Very fast autotune: 1sec
The STM32F407G-DISC1 evaluation board can be used.
So you need only 2 additional oscillators and some potentiometers and switches.
(Values of pitch oscillator)
The oscillators can be built up on a breadboard:
| Component | Pitch | Volume | Price |
|---|---|---|---|
| C1 | 150pF | 180pF | 0.05$ |
| C2 | 150pF | 180pF | 0.05$ |
| C3 | 330pF | 390pF | 0.05$ |
| C4 | 1µF | 1µF | 0.05$ |
| R1 | 2M2 | 2M2 | 0.05$ |
| R2 | 1k | 1k | 0.05$ |
| R3 | 10R | 10R | 0.05$ |
| IC1 | CD4069UBE | CD4069UBE | 0.48$ |
Suppliers: m: www.mouser.com f: www.farnell.com / www.newark.com d: www.digikey.com
L1 should be an air-coil with 1mH. Eg. 200 windings of 0.15mm wire on a core with 40mm diameter.
Use http://hamwaves.com/antennas/inductance.html for other diameters.
| Name | PIN Name | Connector | Description |
|---|---|---|---|
| GND | GND | P1 | Ground for oscillators and potentiometers |
| VDD | VDD | P1 | 3V supply for oscillators and potentiometers |
| PITCH_OSC | PE9 | P1 | Signal from pitch oscillator |
| VOLUME_OSC | PE11 | P1 | Signal from volume oscillator |
| ANALOG_1 | PA1 | P1 | Analog input from volume potentiometer |
| ANALOG_2 | PA2 | P1 | Analog input from zoom volume potentiometer |
| ANALOG_3 | PA3 | P1 | Analog input from shift pitch potentiometer |
| ANALOG_4 | PC4 | P1 | Analog input from zoom pitch potentiometer |
| ANALOG_5 | PC5 | P1 | Analog input from waveform potentiometer |
Connect an extra 100nF capacitor under each potentiometer from the potentiometer output to GND.
The blue button on the STM32 discovery board starts the Auto-Tune procedure.
You can also use an additional button and connect it to:
| Name | PIN Name | Connector | Description |
|---|---|---|---|
| VDD | VDD | P1 | 3V supply auto-tune button |
| Auto-tune | PA0 | P1 | Signal from auto-tune button |
Optional display to show the current played note one a piano like display.
Connect 3mm LEDs with a series resistor of 100R to these PINs and connect all cathodes of to GND:
| Name | PIN Name | Connector | Description |
|---|---|---|---|
| PITCH LED 0 | PE12 | P1 | Note c |
| PITCH LED 1 | PE14 | P1 | Note cis |
| PITCH LED 2 | PE15 | P1 | Note d |
| PITCH LED 3 | PB11 | P1 | Note dis |
| PITCH LED 4 | PB12 | P1 | Note e |
| PITCH LED 5 | PB13 | P1 | Note f |
| PITCH LED 6 | PB14 | P1 | Note fis |
| PITCH LED 7 | PB15 | P1 | Note g |
| PITCH LED 8 | PD8 | P1 | Note gis |
| PITCH LED 9 | PD9 | P1 | Note a |
| PITCH LED 10 | PD10 | P1 | Note b |
| PITCH LED 11 | PD11 | P1 | Note h |
The STM32 discovery board must be supplied by 5V (100mA). It is importand that the GND is connected to earth (PE). If a normal wall adapter is used, there must be an extra connection to earth (PE).
The best power supply would be a linear one like this: https://github.com/gerdb/tinnitus32/wiki/Power-supply
It's possible to store a *.WAV or a *.C file on an USB-stick and use it as sound source for the theremin.
The file name must be WAV1.WAV and it must contain 1 periode of a sound sample. File format must be WAV (Microsoft) and the data format signed 16 bit PCM with only one mono track. Use Audacity to export it. https://www.audacityteam.org/
The file name must be WAV1.C and it must contain 1 periode of a sound sample. File format must be the same as the Audio Wavetables from the Open.Theremin V3 project. http://www.gaudi.ch/OpenTheremin/index.php/download/audio-wavetables
You find the binary file in the "Binary" folder. Download the tinnitus project as ZIP
Program the STM32 board with the STM32CUBEPROG tool.
As case a wooden wine box could be used.
The cheapest way for a professional looking front panel would be to use the service of a sign manufacturer. For example: https://www.digitaldruck-fabrik.de/werbeschilder/hart-pvc-polystyrolplatte.aspx
Price of a 380x110mm front panel is about 4€ or 5$
You can use the template under hardware/Frontpanel, but you have to adapt the size of the front panel file to your wine box. Use eg. https://inkscape.org
