Clipping (audio)

Encyclopedia : C : CL : CLI : Clipping (audio)

Clipping is one form of distortion that occurs when an amplifier is overdriven, which happens when it attempts to increase voltage or current beyond its limits.

The picture shows an oscilloscope screen of an amplifier "clipping." The amplifier should be outputting a clean sine wave, but instead the top and bottom of the waveform is cut off, or "clipped." This can be observed because the tops and bottoms of the wave, which should be rounded, are flat. The term "clipping" is used because the top and bottom of the waveform appear to visually have been "clipped" with a pair of scissors or shears.

When an amplifier is asked to create a signal greater than its maximum capacity, 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 "clipped." The extra signal which is beyond the capability of the amplifier is simply cut off, resulting in a fixed signal. Note that this fixed signal suffers from other forms of distortion, such as total harmonic distortion.

Many electric guitar players intentionally overdrive their guitar amplifiers to cause clipping in order to get a desired sound. See Guitar distortion. Amplifiers with vacuum tubes are often considered to have a better sound.

All amplifiers will clip at some point.

In high fidelity systems, the signal from an amplifier operating in clipping has two characteristics that could damage a connected loudspeaker:

• Because the clipped waveform has more area underneath it than the smaller unclipped waveform, the amplifier produces more power in clipping. This extra power can damage any part of the loudspeaker, including the woofer or the tweeter.
• The clipping introduces additional high frequency components, meaning the clipped signal will be weighted more towards treble than the unclipped signal. Some people believe this additional treble weighting is dangerous to tweeters. Others believe that it is not dangerous, noting that normal music recordings sometimes have significant treble energy (e.g. from an effects pedal which overdrives into clipping) and yet don't damage tweeters.

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 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.

See also

• Loudness war
• Valve sound
• Clipper

External Links

• [Clipping and speaker damage]

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.