DIY semi modular audio synthetizer / stylophone

Who we are, and what we're doing

We are team of lectuers at freetime electronic club for kids in Lužánky Brno.

Every school year multiple times a week we have freetime club meetings with kids interested in electronics and programming from 10 to 18 years old. The electronics club usually have about 20-25 kids .

We as a tem have to make sure that these kids will have best experience possible, which is in our experiences come from making some sort of long-time project requiring lots of soldering and patience to get it to work. Last year we prepared fully programmable LED matrix display whose construction took large portion of school year.

Club meeting usually consists of theoretical part and constuction part. In theoretical part we try to explain function portion of circuit they are about to solder etc. After they solder their circuit we usually test the circuit via osclilloscope and multimeter so kids get confortable using these instruments.

Project Descript__ion

This year we watned something big and interesting, as mentioned above our best bet for last year was big matrix LED display, but beacuse many kids in our club remain for many years we cannot make same project every year. so we decided to design this analog synth.

The synthetizer itself consists of many separate modules connected only by supply traces on one PCB, and by connecting signals from and to those modules with external wires via inserting them to sockets we can make almost any combination of different modules to make unique sounds and beats. The synth consists of:

Differential power supply delivering 12v and -12v

Raspberry pico with MIDI in and out extension, 4x PWM to analog converters and 3x ADC inputs

2x stylophone-like resistor divider rails

2x exponential VCO (voltage controlled oscillator)

2x LFO (low frequency osclillator)

2x envelope generator

3x VCA (voltage controlled amplifier)

2x drum-like oscillator

2x signal mixer

soft signal clipper

wavefolder

resonant diode bridge low pass filter

resonant diode bridge high pass filter

I2C OLED display

6x cherry MX mechanical keyboard switches with LED

3.5mm jack output or automatically selected class AB speaker output amplifier

lots of LEDs

GPIO pin header for extensions (9 free GPIOs)

It is quite easy to 3d print extension like keyboard instead of stylus, which would make this synth more piano-like.

Its 12V input and quite low power consumption (<100mA) makes it possible to be powered by batteries.

If you have any quescions or advices feel free to contact us.

Words to PCBWay

We are hoping PCBWay will be able to help us by sponsoring our analog synthetizer board. We have put countless hours in the careful design, and re-design of this board to make full use of PCBWay's manufacturing capabilities. We hope that this is enough to convince PCBWay to manufacture us these boards which woud othervise cost us about 190$ for 25 boards, which would otherwise upset our yearly budget for our electronic kids/students.

Render in Fusion 360

Board in Eage