Amplification - Distortion by saturation

Now let's see what this implies in terms of sound itself. As we have already seen in its pertaining section, a sinusoidal signal comprises of one single frequency [Pure sinusoid ] , equal to the number of cycles that the sinusoid itself undergoes per second. However if we consider a signal that has many sudden transitions, it will have other frequencies. So, a signal that has sudden transitions in time, has not just one, but a series of frequencies. The more sudden the transitions the higher the frequencies needed to reproduce them. In connection to this last point, let's not forget that a rectangular wave [Square Wave ] has instantaneous transitions (this is a theoretical abstraction which doesn't exist in real life, seeing that amplitude transitions can never occur in a 0 sec time interval). To represent a signal of this kind we'd need an infinite amount of sinusoids with ever-increasing frequencies, thus in fact we'd need infinite frequencies (this also is clearly an abstract theory).

So we see that by severing the sinusoid's peak, the amplifier imposes some transitions onto the signal that are not contained in the original one. This generates new frequencies which also weren't present in the original signal, and this is what causes the distortion. So, unless we are seeking to use distortion as an effect, input voltage must always remain within the amplifier's specific limits regarding the input signal.