  P  R  D  X  L


  A PARADOXICAL SOUND SYNTHESIZER
  by Thierry Rochebois 1/2/94
     email: thierry@marion.ief-paris-sud.fr


Paradoxical Sounds

  The main property of paradoxical sounds is that
  their frequency do not change when you go an
  octave higher. This property is achieved thanks
  to an appropriate spectrum modelling as shown
  in the picture file paradoxi.gif.

PRDXL

  Prdxl is a wave table paradoxical sound synth.
  I built a basic prototype of this synth this
  summer.
  Its schematics are shown in the picture file
  prdxl.gif. The EPROM is filled with the 12
  paradoxical tables. Its contents can be found
  in the file prdxl.hex: an hex code per line
  in ASCII format (32k lines). I hope that every
  EPROM programmer can read this kind of raw 
  file format.


The schematics can be divided in two parts:


  THE KEYBOARD ENCODER

    It encodes the 12 keys in a 4 bit format and
    generate a gate signal.
    This is not the most interesting part of the
    schematics.

  THE WAVE TABLE READER

    It reads the wave table addressed by the 4
    bit key code. A dac transforms the binary
    output data into analog signal.
    This is the must interesting part to build
    (you can test it by simulating the 4 bit
    key code and the gate signals with switches,
    but playing music in binary code is not very
    easy!). A basic envelop is implemented as
    a capacitor on the ref voltage pin of the
    DAC, you can improve it by using a true
    ADSR and a true VCA (or by using modules
    of the synth you own).


  Nota: these schematics are basic and can be
  improved by adding modules such as filters,
  ADSR,VCA, sequencer and so on.


