Analog to Digital Conversion

• sample-and-hold: the instantaneous signal voltage is sampled at regular intervals and held constant between intervals, resulting in sampling errors from the the replacement of a varying signal by a step signal (constant on the regular intervals)
• quantization: the held voltage is converted to the nearest integer value (in some fixed unit such as 0.001 volt.) resulting in quantization errors of up to ± ½ LSB (eq., ± 0.0005 volt)

Surprisingly, by the sampling theorem, if the sampling rate is greater than twice the frequency of the highest component of the input signal, then no information is lost due to sampling errors as the original analog signal may be recovered from the sampled signal! Thus by using a sample rate which exceeds twice the upper limit for hearing and a sample resolution sufficient to reduce the quantization error to below the threshold of hearing we may recover an analog signal which has no audible differences from that of the original. (See High resolution digital audio -- can you tell the difference?)

The quantization error is the difference between the sampled analog signal and the digitized signal:

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