Emulation of Operational Amplifiers and Diodes in Audio Distortion Circuits

Authors
Rafael Cauduro Dias de Paiva1, Stefano D'Angelo1, Jyri Pakarinen1, Vesa Välimäki1
Status
Published in IEEE Transactions on Circuits and Systems II: Express Briefs, vol. 59, no. 10, pp. 688–692, October 2012
DOI
10.1109/TCSII.2012.2213358
1
Aalto University, Espoo, Finland
BibTeX
@article{depaiva2012opamp,
  title={Emulation of Operational Amplifiers and Diodes in Audio Distortion Circuits},
  author={de Paiva, Rafael Cauduro Dias and D'Angelo, Stefano and Pakarinen, Jyri and V\"alim\"aki, Vesa},
  journal={IEEE Trans. Circ. Systems II: Express Briefs}, 
  volume={59},
  number={10},
  pages={688--692},
  month={10},
  year={2012},
  doi={10.1109/TCSII.2012.2213358}
}

Abstract

This brief 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 brief 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 (WDFs). 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 lookup table per output sample.

Implementation

Sound samples