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The spec is defined in percentage of purity in harmonics to the actuals. Distortion derived from the creation of harmonics (multiples of a base frequency signal) in an audio system adding additional frequency peaks to the output. This specification is applicable to cassette decks, amplifiers etc. Harmonics are multiples of the original signal being reproduced by an audio system. For instance, if a signal at 2 kHz is being produced by an audio system, harmonics would be located at 4 kHz, 6 kHz, 8 kHz, 10 kHz and so on with each progressive frequency being smaller than the one before.
This type of distortion affects the audio signal by adding to it frequencies that were not included and not meant to be reproduced. Total harmonic distortion figures are derived by feeding a pure sine wave into an audio component and then measuring the amplitude of the fundamental (the original pure sine wave being input) and its harmonics. Amplitude is the height of a sign wave from the base level to its peak. Signals with greater amplitude are louder or more powerful. The amplitudes of harmonics are smaller than that of the original signal (fundamental). By dividing the amplitudes of the harmonics by the amplitude of the fundamental (the original pure signal), a THD figure can be generated. Look for low THD figures preferably of 0.5% or less. Anything lower than .5 % will not even be noticed. But some of the amps coming in our product list even upto .05% are affordable for medium category budget customers
THD+N (Total Harmonic Distortion plus Noise) Combination of total harmonic distortion (THD) with noise to achieve a complete figure representing distortions present in an electronic component with lower levels below one percent being preferable (see THD and Noise). |
