The influence of program material on the nonlinear behavior of audio power amplifiers driving complex loads

Nonlinear distortion of an audio power amplifier is conventionally characterized by total harmonic distortion and other similar values, provided that it is excited by a sinusoidal signal and that it drives a resistive test load. In this paper, thoroughly selected segments of musical signals were fed to power amplifiers driving a complex load designed on a statistical basis. Output voltage and current waveforms, were digitized by means of a A/D acquisition system and projected in the V-I plane. The probability density function was computed and nonlinear operation of amplifiers was successfully traced in the same plane. The isolation of the nonlinear operation area and the evaluation of its associated probability value, provided a quantitative measure of amplifier nonlinear distortion, under music reproduction. It also became evident, that several other conclusions concerning design procedures of such devices, can easily be derived.