Virtual Analog Model of the Lockhart Wavefolder
Fabián Esqueda, Henri Pöntynen, Julian D. Parker and Stefan Bilbao
Companion page for a paper in the 14th Sound and Music Computing Conference (SMC-17)
Espoo, Finland, 5 — 8 July 2017
Original paper available here.
Abstract
This work presents a novel virtual analog model of the Lockhart wavefolder. Wavefolding modules are among the fundamental elements of West Coast style analog synthesis. These circuits produce harmonically-rich waveforms when driven by simple periodic signals such as sinewaves. Since wavefolding introduces high levels of harmonic distortion, we pay special attention to suppressing aliasing without resorting to high oversampling factors. Results obtained are validated against SPICE simulations of the original circuit. The proposed model preserves the nonlinear behavior of the circuit without perceivable aliasing. Finally, we propose a practical implementation of the wavefolder using multiple cascaded units.
MAX/MSP Demo
Click here to download a MAX/MSP demo of the proposed virtual analog demo of the Lockhart wavefolder implemented using Gen~.
Matlab Files
Click here to download an example implementation of the Lambert-W function evaluated using Fritsch's iteration.
Errata
Unfortunately, it has been brought to our attention that there are a few mistakes in the paper. The corrections are available in the following document: Errata.