Walsh 32 Generator. www.haraldswerk.de

Motivation

This is is the realization I dreamed of for a long time. A Walsh function generator. This one generates the first 32 Walsh functions. They are mixed together with potentiometers, so you can dial in the waveform you want at the output. I have grouped the outputs in four groups for experimenting with different numbers of partials (7, 15, 23, 31). Those four outputs are only slightly low pass filtered with fixed cutoff frequency. For usage I recommend to use the raw output add on and go through a proper voltage controlled filter using the same control voltage as the driver VCO. I drive the Walsh Generator from my High Speed VCO. Which gives a max output frequency of 7.5kHz. This should be enough for audio use. You can go higher though. There is a method to calculate waveforms described by Benjamin Franklin Jacoby PhD in "Walsh Functions, A Digital Fourier Series" Byte Book of Computer Music pg65ff or Byte Magazin September 1977. I used this article intensively for this build. The other one used was from Electronotes Supplement S-008 pg5ff. You can find other sources for Walsh functions on the net as well. Including interactive Walsh generators. There is a other add on module which gives access to the individual Walsh functions

Specs and features

31 one individual adjustable Walsh partials
Four grouped outputs 1-7, 1-15, 1-23, 1-31
Individual volume control per group
Outputs for add on on the back. Raw out and singles out
Power consumption below 15mA each rail

Implementation

Schematic

Walsh 32 Function Generator Walsh functions — Walsh 32 Function Generator: Walsh functions

Walsh 32 Function Generator schematic 02 main board — Walsh 32 Function Generator schematic: Main board 02

Walsh 32 Function Generator schematic control board A1 — Walsh 32 Function Generator schematic: Control board A1

Walsh 32 Function Generator schematic control board F2 — Walsh 32 Function Generator schematic: Control board F2/01

Description:

The logic circuitry is a combination from Electronotes Supplement S-008 pg5ff and Benjamin Franklin Jacoby PhD in "Walsh Functions, A Digital Fourier Series" Byte Book of Computer Music pg65ff or Byte Magazin September 1977. You can look up the detailed description there. The rest are just potentiometers to add the functions and four standard low pass filters.

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