Specifications

Appendix A - Digital Recording Concepts
ADAT LX20 Reference Manual 73
APPENDIX A
DIGITAL RECORDING
CONCEPTS
ANALOG RECORDING BASICS
Digital recording works very differently from analog recording. With analog
recording, tape containing millions of tiny magnetizable particles move past a
record head. The magnetic field around this head fluctuates according to the audio
signal present at the tape recorder’s input. These fluctuations permanently
rearrange the particles on the tape to form a pattern that is analogous to the
original audio signal.
On playback, the patterns on tape are read by a separate playback head (or from
the record head, set up to read instead of record signals) that converts the magnetic
fluctuations back into an audio signal.
The biggest problem with analog recording is that the tape itself alters the sound
originally recorded on tape. Tape hiss is one problem; it superimposes a low-level
rushing noise onto the audio signal. Although there are ways to minimize noise,
such as noise reduction circuitry, this colors the sound in the process of masking the
noise.
Tape’s frequency response is also an issue. Tape has a hard time “absorbing” higher
frequencies, which can dullen the sound. Moving tape faster allows the heads to
magnetize more particles and extends the high frequency response, but the tradeoff
is increased tape costs, and heftier transports to move bigger reels of tape.
DIGITAL RECORDING BASICS
With digital recording, the technology is similar — tape moves past a record head,
and plays back through a playback head. However, the signal recorded on tape is
very different.
Audio signals entering each channel of the LX20 first pass through an analog-to-
digital (A/D) converter, a device that takes 48,000 samples or “snapshots” of the
signal level every second
1
. Each sample is assigned a specific numeric value that
corresponds to its level.
1
48,000 samples are taken per second at a sampling rate of 48 kHz; 44,100
samples are taken per second at a sampling rate of 44.1 kHz.