Virtual analog Buchla 259 wavefolder

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Journal Title
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Volume Title
Conference article in proceedings
Date
2017
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Language
en
Pages
8
192-199
Series
Proceedings of the 20th International Conference on Digital Audio Effects, Proceedings of the International Conference on Digital Audio Effects
Abstract
An antialiased digital model of the wavefolding circuit inside the Buchla 259 Complex Waveform Generator is presented. Wave-folding is a type of nonlinear waveshaping used to generate complex harmonically-rich sounds from simple periodic waveforms. Unlike other analog wavefolder designs, Buchla's design features five op-amp-based folding stages arranged in parallel alongside a direct signal path. The nonlinear behavior of the system is accurately modeled in the digital domain using memoryless mappings of the input-output voltage relationships inside the circuit. We pay special attention to suppressing the aliasing introduced by the nonlinear frequency-expanding behavior of the wavefolder. For this, we propose using the bandlimited ramp (BLAMP) method with eight times oversampling. Results obtained are validated against SPICE simulations and a highly oversampled digital model. The proposed virtual analog wavefolder retains the salient features of the original circuit and is applicable to digital sound synthesis.
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Citation
Esqueda , F , Pöntynen , H , Välimäki , V & Parker , J D 2017 , Virtual analog Buchla 259 wavefolder . in Proceedings of the 20th International Conference on Digital Audio Effects . Proceedings of the International Conference on Digital Audio Effects , University of Edinburgh , pp. 192-199 , International Conference on Digital Audio Effects , Edinburgh , United Kingdom , 05/09/2017 . < http://www.dafx17.eca.ed.ac.uk/papers/DAFx17_paper_82.pdf >