PB701 Electric Intonarumori

The core of that noise board is the digital delay chip PT2399. It has some OpAmps build in to filter the sound and do the echo. In this application everything that helps to get rid of the noise of the chip itself was avoided, that leads into a self sustainable noise source.

The board is based on a design of the Chaos Looper by Urs Gaudenz from Gaudi Labs and from the Schweizer Gesellschaft Für Mechatronische Kunst - thanks for that!
I added the voltage control of the delay and some extra functions, like the noise on/off, the boost and the mute function to the circuit.

The “echo” could be changed with a potentiometer, the “delay” with CV (0 to 5V) or with a potentiometer. An other Low Pass filter could be changed with the third potentiometer.

The Electric Intonarumori has an audio and an control voltage input, while building the board one has to choose between bus 1 and bus 2 for the audio input and one has to use the other bus for the control input.

The board is an homage and is named after the instrument “Intonarumori” of the Italian Futurist, painter, composer and the author of the manifesto The Art of Noises, Luigi Russolo.


Thanks to Taymur Streng for the reverse engineering of the circuit, I never manged to make any schematics of it.

Paper PCB


  • Resistors:
  • 1x 330 Ohm
  • 1x 220 Ohm
  • 1x 1 kOhm
  • 5x 2 kOhm
  • 1x 4,7 kOhm
  • 1x 5,6 kOhm
  • 1x 20 kOhm
  • Capacitors:
  • 1x 1 nF (foil)
  • 1x 4.7 nF (foil)
  • 1x 39 nF (Foil)
  • 5x 100 nF (foil)
  • Electrolytic Capacitors:
  • 1x 4,7 µF
  • 1x 10 µF
  • 1x 47 µF
  • Semiconductors:
  • digital delay PT 2399
  • optocoupler TLP521
  • 1x LED
  • Mechanical:
  • 1x IC socket, 16 pin
  • 1x IC socket, 4 pin
  • 1x pin strip 1×9
  • 2x pin header, female 90° 1×3, 1×2
  • 2x pin header, male 90° 1×3, 1×2
  • 3x mini switch
  • 3x push button
  • 3x jumpers
  • Potentiometers:
  • 2x 10k
  • 1x 100k


The PB701 Electric Intonarumori was designed by Wolfgang Spahn, 2017-20.
It is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Creative Commons License