62 lines
1.6 KiB
Plaintext
62 lines
1.6 KiB
Plaintext
P R D X L
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A PARADOXICAL SOUND SYNTHESIZER
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by Thierry Rochebois 1/2/94
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email: thierry@marion.ief-paris-sud.fr
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Paradoxical Sounds
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The main property of paradoxical sounds is that
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their frequency do not change when you go an
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octave higher. This property is achieved thanks
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to an appropriate spectrum modelling as shown
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in the picture file paradoxi.gif.
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PRDXL
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Prdxl is a wave table paradoxical sound synth.
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I built a basic prototype of this synth this
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summer.
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Its schematics are shown in the picture file
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prdxl.gif. The EPROM is filled with the 12
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paradoxical tables. Its contents can be found
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in the file prdxl.hex: an hex code per line
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in ASCII format (32k lines). I hope that every
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EPROM programmer can read this kind of raw
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file format.
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The schematics can be divided in two parts:
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THE KEYBOARD ENCODER
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It encodes the 12 keys in a 4 bit format and
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generate a gate signal.
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This is not the most interesting part of the
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schematics.
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THE WAVE TABLE READER
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It reads the wave table addressed by the 4
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bit key code. A dac transforms the binary
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output data into analog signal.
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This is the must interesting part to build
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(you can test it by simulating the 4 bit
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key code and the gate signals with switches,
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but playing music in binary code is not very
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easy!). A basic envelop is implemented as
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a capacitor on the ref voltage pin of the
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DAC, you can improve it by using a true
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ADSR and a true VCA (or by using modules
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of the synth you own).
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Nota: these schematics are basic and can be
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improved by adding modules such as filters,
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ADSR,VCA, sequencer and so on.
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