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Project Notes

#239 AudioDSP/SuperCrunch

AudioDSP crunchy symmetrical Schetzen distortion effect based on the pedalSHIELD.



SuperCrunch.ino is a crunchy distortion effect from the pedalSHIELD examples. The pushbuttons control the volume of the output signal.

Core algorithm:

  • distortion is derived on a symmetrical clipping system based on Schetzen formula

Schetzen Formula for symmetrical soft clipping is as follows:

         { 2*x                for  0  <= |x| <= 1/3  }
f(x) =   { (3-(2-3*x)^3)/3    for 1/3 <= |x| <= 2/3 }
         { 1                  for 2/3 <= |x| <= 1   }


A vast improvement on the asymmetrical Crunch, and a much warmer fuzz than the simple clipping of Distortion.

Delivers quite a warm crunch with pretty good frequency response, although the upper registers of the guitar are a bit beyond the capability of the Arduino.

AudioDspDriver Library

This example uses a private AudioDspDriver library that contains my refactoring of the core algorithms for driving the board. I may split this out as a stand-alone library at some point.



The Schematic


Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.