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Clipping is a form of distortion that occurs when an amplifier is overdriven, which happens when it attempts to increase voltage or current beyond its limits.
When an amplifier is pushed to create a signal with more power than it can support, it will amplify the signal only up to its maximum capacity, at which point the signal will be amplified no further. As the signal simply "cuts" or "clips" at the maximum capacity of the amplifier, the signal is said to be "clipping." The extra signal which is beyond the capability of the amplifier is simply cut off, resulting in a distorted waveform.
Many electric guitar players intentionally overdrive their guitar amplifiers to cause clipping in order to get a desired sound. See Guitar distortion.
All amplifiers have a maximum amount of power, so theoretically they all can clip. However, many amplifiers will not allow a user to turn gain up beyond that point, so that the amplifier never clips. This is sometimes to reduce accidental distortion, or more importantly, to keep from damaging the amplifier as some amplifiers cannot withstand the heat generated by some forms of clipping.
In power amplifiers, the signal from an amplifier operating in clipping has two characteristics that could damage a connected loudspeaker:
In digital signal processing, clipping occurs when the signal is restricted by the range of a chosen representation. For example in a system using 16-bit signed integers, 32767 is the largest positive value that can be represented, and if during processing the amplitude of the signal is doubled, sample values of 32000 should become 64000, but instead they are truncated to the maximum, 32767. Clipping is preferable to the alternative in digital systems — wrapping — which occurs if the digital hardware is allowed to "overflow", ignoring the most significant bits of the magnitude, and sometimes even the sign of the sample value, resulting in terrible modification of the signal.
In analogue audio equipment, there are three common causes of clipping.
Some audiophiles believe that the clipping behavior of vacuum tubes is superior to that of transistors, in that vacuum tubes clip more gradually than transistors, resulting in harmonic distortion that is generally less objectionable.