Another Theremin-like instrument

emmanuel63

Well-known member
Hello,
Here is another Theremin ! This one is very simple : a Time of Flight sensor for the pitch, and FSR for volume. The synth section is also very simple, just one oscillator, a LP filter, minimalist LFO and reverb. In fact, this project is designed for workshops, so it has to be simple. The core is a T3.5 that was feeling lonely in my junk box... I use the well known and so cheap PCM5102 as audio DAC. A small 5V class D amp is also included (PAM8403). These amps are difficult to use because they inject so much noise... but they are so efficient ! Real theremins are difficult to master. So I have programmed a "scale mode" to keep the intonation right.

This time, I will publish schematics and large part of the code. This will be done shortly (hopefully) on a dedicated website (see Youtube description).

Emmanuel
 
Great projects. Will you come to the Synfest France? It's a very friendly event where DiY enthusiasts like you and me are welcome. It is located near Nantes and is scheduled in april.
 
Love the "scale mode". Great work!
I restored a 1961 Moog Melodia Theremin for a friend. Quite the challenge to adjust all the tuning coils. Emulating with a Teensy opens up new territory to explore.

BTW, most Theremin's increase the note frequency when the hand approaches. Maybe you could add a switch to flip this feature around.
Moog Theremin Melodia 1961.jpg
 
I will certainly add a switch to choose the orientation of the pitch.
I have tested it quite a lot now, and it is really fun to play. There is of course room for improvements ! I have used a VL53L1X sensor to mesure distance. I appears to be a good compromise for cost and accuracy. But I still need to filter the readings to smooth the sound. I add a little latency. I am looking for a better sensor :
- fast ranging frequency (the fastest it is, the more I can smooth the signal. 100 hz would be great)
- stable reading without noise (easier to filter)

Emmanuel
 
Since the original Theramin heterodyned the oscillator controlled by the hand I believe you could set it to go either way too by choosing high or low local oscillator frequency. Or even to reduce in frequency on approach down to zero and start increasing again if you want! For most purposes you want increasing, as there isn't a high pitched idle tone, especially if you can set the fully distant hand beat frequency to sub-sonic.

With a ToF sensor you've the freedom to set the position->frequency curve to anything you want, which might offer some interesting possibilities.
 
Back
Top