P R D X L
A PARADOXICAL SOUND SYNTHESIZER by Thierry Rochebois 1/2/94 email: email@example.com
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 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.
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