This work presents a generic model to emulate distortion circuits using operational amplifiers and diodes. Distortion circuits are widely used for enhancing the sound of guitars and other musical instruments. This paper introduces a new model for an ideal operational amplifier that does not include implicit equations and is thus suitable for implementation using wave digital filters (WDF). Furthermore, a novel WDF model for a diode is proposed using the Lambert W function. A comparison of output signals of the proposed models to those obtained from a reference simulation using SPICE shows that the distortion characteristics are accurately reproduced over a wide frequency range. Additionally, the proposed model enables real-time emulation of distortion circuits using ten multiplications, 22 additions, and two interpolations from a look-up table per output sample.

Published in

IEEE Transactions on Circuits and Systems. Part II – Express Briefs, vol. 59, no. 10, pp. 688–692, Oct. 2012.

• Dry electric guitar signal #1 An unprocessed electric guitar signal as directly recorded by the sound card.
• PSPICE reference simulation with noninverting distortion..
• Proposed WDF model with noninverting distortion.
• PSPICE reference simulation with inverting distortion..
• Proposed WDF model with inverting distortion.