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Create a synthesizer with a Raspberry Pi

A Raspberry Pi is a credit-card-sized computer in which Polyphone can be installed. By integrating it into a box containing speakers and associating it with a master keyboard, it's possible to create a real synthesizer!

Home-made synthesizer - front
Home-made synthesizer - front
Home-made synthesizer - back
Home-made synthesizer - back

Materials required

This list can be adapted to suit your project:

  • a Raspberry Pi,
  • a micro SD card with a capacity of 32 GB or more,
  • a power supply for the Raspberry Pi,
  • an analog/digital converter (DAC) to transform a USB output into an audio jack,
  • computer speakers, which have the advantage of containing both the speakers and the signal amplification part,
  • a general on/off switch,
  • a 2x male to female USB flush mount cable,
  • a case to put everything inside,
  • and of course a master keyboard for playing.

To easily configure the Raspberry Pi, it is recommended to also have:

  • a screen with a mini-HDMI cable for the connection to the Raspberry Pi,
  • a keyboard,
  • a mouse.

In the example on this page, second-hand Edifier R1280T speakers have been used. For a modest price, they are capable of reproducing low tones relatively well, and as you will see below, it will be possible to correct frequency response shortcomings.

The master keyboard used is an Akai MPK Mini Plus, connectable via USB. The USB / jack adapter is a first-price UGREEN and the Raspberry Pi is version 5.

(the aim of these details is not to advertise any particular brand, but to present a combination that works)

Preparing the box

This tutorial will not focus on one particular way of making a box. The use of wood will showcase your carpentry skills, as in this example, but cardboard can work just as well. It's up to you to express your creative talents! Overall, you will need a cover to access the components, and openings for:

  • the speakers,
  • the power cable,
  • the on/off switch,
  • the volume and - if necessary - equalization knobs,
  • the Helmholtz resonators for the bass-reflex, and so on.

A suggested order of installation in the box is as follows:

  • start by recessing the on/off button, the USB connectors on the rear panel and any other buttons connected to the speakers,
  • place the power cable and connect it to the input of the on/off button,
  • place the transformer associated with the speakers and connect it to the output of the on/off button,
  • place the speaker circuit board and connect it to the transformer,
  • attach the speakers and connect them to the circuit board,
  • attach the Raspberry Pi,
  • connect the Raspberry Pi power supply to the output of the on/off button (the output of the button supplies power to both the speakers and the Raspberry Pi),
  • connect the double USB cable to the Raspberry Pi,
  • connect the USB/jack converter to another USB socket,
  • connect the speaker circuit board via a jack cable.

In the following image, the power supply and the electronic board related to the speakers are circled in orange. The Raspberry Pi is circled in blue.

Inside the synthesizer
Inside the synthesizer

Note: speakers must be placed so that there is no possible return of sound between the speaker output and the inside of the box, otherwise a resonance will appear. So not like in this example! Sometimes we need to experiment to discover traps...

The Raspberry Pi
The Raspberry Pi

3 USB ports are used:

  • one to obtain a jack output,
  • the other 2 are redirected to the back of the box and will be used to connect the master keyboard or, when configuring the Raspberry Pi, a keyboard and a mouse.

(more coming soon)

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