The advantages of digital techniques were first realized in the field of magnetic recording. Analog magnetic recording creates significant deterioration of the original sound: using analog techniques, for example, it is difficult to obtain a flat frequency response at all signal levels. Furthermore, the signal-to-noise ratio is limited to some 70 dB, the sound deteriorates by speed variations of the recorder mechanism, crosstalk and print-through problems arise, and any additional copying deteriorates the characteristics even further. In addition to this, to keep the equipment within close specifications, as required in a professional environment, frequent and costly realignment and maintenance are required.
Digital magnetic recording, on the other hand, solves virtually all of these drawbacks. Recording of digital data, however, presents some specific problems:
Several different techniques have been developed, outlined in the following chapters.