Slew-induced distortion (SID or slew-rate induced distortion) is caused when an amplifier or transducer is required to change output (or displacement), i.e.
slew rate
In electronics, slew rate is defined as the change of voltage or current, or any other electrical quantity, per unit of time. Expressed in SI units, the unit of measurement is volts/second or amperes/second, but is usually expressed in terms of m ...
, faster than it is able to do so without error. At such times any other signals may suffer considerable gain distortion, leading to
intermodulation distortion
Intermodulation (IM) or intermodulation distortion (IMD) is the amplitude modulation of Signal (electrical engineering), signals containing two or more different frequencies, caused by non-linear, nonlinearities or time variance in a system. ...
.
[http://www.aes.org/par/i/#IM AES Pro Audio Reference for Intermodulation Distortion] Transient intermodulation distortion may involve some degree of SID and/or
distortion
In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signa ...
due to peak compression.
These are effects that tend to occur only during parts of a
waveform fed through
audio amplifier
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...
s, that may give rise to audible degradation of the sound quality in music, even when fixed-
frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
harmonic distortion
In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal ...
tests show low amounts of distortion for a simple
sinewave test signal.
TIM (Transient Intermodulation Distortion) was first discovered by Matti Otala in the 1960s due to accidentally wiring an amplifier incorrectly.
References
Audio effects
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