Why is it that the higher the listening level, the more distortion occurs in an output waveform signal?

Question

In a complementary push pull amplifier circuit, it was observed in our experiment that the higher the listening level (or the higher the amplitude of a wave) the more pronounced the distortion is...why is this so? moreover, at low listening levels, there hardly occured any distortion...Can someone explain this situation in detail?

Answer 1

Look at a graph of the transfer function of your amplifier. Since you use the term "push-pull amplifier" I am assuming that you are also OK with "transfer function".

At low levels, the plot is (should be, anyway) linear. When the output is linearly related to the input, you hear no distortion (at least none from the amplifier - you might have some distortion from speakers or other components).

As the level increases, you reach a point where the transfer function reaches nonlinearity and distortion begins. As the signal gets large enough, you reach a point of clipping, where - no matter how much more input you provide -  the output remains the same. At the clipping point, distortion becomes really noticeable and particularly annoying.