Editing Distortion (section)

==Correction of distortion==
As the system output is given by y(t) = F(x(t)), then if the inverse function F<sup>−1</sup> can be found, and used intentionally to distort either the input or the output of the system, then the distortion is corrected.

An example of a similar correction is where LP/[[gramophone record|vinyl]] recordings or [[FM broadcasting|FM audio]] transmissions are deliberately pre-emphasised by a [[linear filter]], the reproducing system applies an inverse filter to make the overall system undistorted.

Correction is not possible if the inverse does not exist—for instance if the [[transfer function]] has flat spots (the inverse would map multiple input points to a single output point). This produces an uncorrectable loss of information. Such a situation can occur when an amplifier is overdriven—causing [[clipping (audio)|clipping]] or [[slew rate]] distortion when, for a moment, the amplifier characteristics alone and not the input signal determine the output.

===Cancellation of even-order harmonic distortion===
Many symmetrical [[electronic circuits]] reduce the magnitude of even harmonics generated by the non-linearities of the amplifier's components, by combining two signals from opposite halves of the circuit where distortion components that are roughly the same magnitude but out of phase.  Examples include [[Push–pull output|push-pull amplifiers]] and [[long-tailed pair]]s.