Antex Electronics SX-26 Digital Audio Adapter User Manual
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In digital-to-analog conversion, the PCM bitstream is converted at
the sampling frequency to a continuously changing series of
quantization levels which are individual "steps" of discrete voltage
equal to the quantization levels in the analog-to-digital process.
The shape of this continuously changing stream of quantization
levels approximates the shape of the original wave. This is shown
in the top half of Figure 2. This signal is then passed through a low-
pass filter, which removes the digital "switching noise." The end
result, shown in the bottom half of Figure 2 is an analog output
signal whose waveshape is a very close approximation of the
original analog input signal. The foregoing is a very brief and, of
necessity, oversimplified explanation of how digital audio works.
For the interested reader, the book Principles of Digital Audio by
Ken C. Pohlmann, copyright 1985 by Howard W. Sams, is highly
recommended.