Nonlinear Processing: Distortion, Tube Simulation, and HF Exciters
Will C. Pirkle · 2019
The time domain transfer functions do a good job at describing the effect of the nonlinear amplification on the waveform. It is easy to see the difference between the hard clipped and soft clipped waveforms insomuch as how they modify the shape of the signal. All nonlinear processing algorithms will add harmonics to the original signal. A perfect sinusoid has a frequency domain magnitude response that consists of a single spike at the sinusoidal frequency. When linearly processed, the output signal may have a different magnitude and/or phase, but the spectrum consists of that single spike representing the sinusoid. The number, size, and amplitude ratios of these harmonics determine how the original sound is altered to change its timbre. These added harmonics will cause aliasing if they exist above the Nyquist frequency.