Virtual analog modeling is needed when simulating classic analog circuitry by DSP, for example, when emulating analog sound systems. In this paper we show how wave digital filters (WDFs) can be applied to efficient real-time simulation of vacuum-tube amplifier stages, typical in professional guitar amplifiers, which pose nonlinear behavior for desired distortion effects.

Published in the IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP), May 14-19, 2006, Toulouse, France.

Medium gain
• Dry electric guitar signal #1 An unprocessed electric guitar signal as directly recorded by the sound card.
• Commercial amplifier modeling software. Medium gain. The previous signal processed by a commercial amplifier modeling software, medium gain.
• Our WDF modeling algorithm. Medium gain. Dry electric guitar signal #1 processed by our WDF modeling algorithm, medium gain.
High gain
• Dry electric guitar signal #2 Another unprocessed electric guitar signal as directly recorded by the sound card.
• Commercial amplifier modeling software. High gain. The previous signal processed by a commercial amplifier modeling software, high gain.
• Our WDF modeling algorithm. High gain. Dry electric guitar signal #2 processed by our WDF modeling algorithm, high gain.

In the sound samples above, both amplifier simulations, the commercial and WDF-model, also provide a loudspeaker emulation. In the case of our WDF-model, the emulation is a simple lowpass filter with cutoff frequency at 5 kHz and a 6 dB notch at 1.2 kHz.