P R D X L
A PARADOXICAL SOUND SYNTHESIZER
by Thierry Rochebois 1/2/94
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 is a wave table paradoxical sound synth.
I built a basic prototype of this synth this
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
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
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.
The Intel Hex File for the EPROM
The Binary File for the EPROM