Hard clipping is a type of distortion effect where the amplitude of a signal is limited to a maximum amplitude. This effect can be created in the analog or hardware world when a transistor is pushed to a maximum amplitude. At this amplitude, the transistor saturates and cannot output a signal above a specific level, so the input signal is clipped.
This type of distortion effect can also be created using software. This is accomplished by detecting when the amplitude of a signal goes above a specified threshold. If the amplitude of the signal goes above the threshold, then the amplitude is assigned a new value (resulting in clipping).
Audio signals have positive and negative amplitude (for compression and rarefaction). In the case of hard-clipping, there should also be a minimum specified amplitude. If the amplitude of the signal goes below the negative of the threshold, then the amplitude is assigned a new value.
An equation to determine the amplitude of a processed or clipped, output signal is the following:
out = thresh, when in > thresh
out = -thresh, when in < -thresh
out = in, otherwise
When implemented in computer code, a conditional statement can be used to perform hard-clipping. In this case, an if statement, an elseif, and an else statement are all necessary to handle the three possible conditions.
Next, let’s look at a different, closely-related type of distortion called soft clipping.