What Is Harmonic Distortion?

- Sep 04, 2018-

Harmonic distortion is a distortion caused by nonlinear components in a power amplifier. This distortion causes the audio signal to generate many new harmonic components that are superimposed on the original signal, creating a waveform-distorted signal. The distortion caused by each harmonic is superimposed, which is the total harmonic distortion, and its value is expressed as a percentage of the ratio of the rms value of all harmonics in the output signal to the effective value of the fundamental voltage. Here, the fundamental signal is the input signal, and all harmonic signals are the harmonic signals introduced by the nonlinear distortion. Obviously, the smaller the percentage is, the smaller the harmonic distortion and the better the circuit performance. At present, the harmonic distortion of Hi-Fi power amplifier is generally controlled below 0.05%, the harmonic distortion of many high-quality power amplifiers is less than 0.01%, and the harmonic distortion of professional-grade audio power amplifiers is generally controlled below 0.03%. In fact, when the total harmonic distortion is less than 0.1%, the human ear is difficult to distinguish. It should also be noted that for a given audio power amplifier, for example, the total harmonic distortion index of an audio power amplifier is expressed as THD < 0.009% (1 W). At first glance, it seems that the total harmonic distortion is small, but it is only the total harmonic distortion at an output power of 1 W, which is different from the total harmonic distortion value obtained under the measurement conditions required by the relevant standards. Therefore, when the total harmonic distortion index of the audio power amplifier is indicated, the measurement conditions are generally indicated.



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