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THE EVOLUTION OF RECORDING
Digital Tape Recorders differed from Magnetic Tape Recorders (Analog) in that they stored digital information about sound rather than the sound itself. Although Digital has its own noise, it does not have the tape hiss associated with Analog magnetic tape. Since Digital stores INFORMATION rather than sound, the most important part of Digital sound quality was the CONVERSION from analog to digital information.
The full path to Digital Audio is: Sound waves that have already been converted (through transducers) from physical (moving in the air) to electrical (even if it has been stored magnetically) can then be converted to DIGITAL AUDIO by passing through an ANALOG TO DIGITAL CONVERTER. The A/D converter analyzes the audio in slices of time. The number of slices per second is the SAMPLE RATE. CD audio consists of 44,100 slices per second. Audio that is used in Digital Video consists of 48,000 slices per second.
BIT DEPTH indicates the amount of information about each slice that is captured and stored. A graphic image with a color depth of 8 bits (with only 256 colors) is not as photo-realistic as a graphic image with 16 bits (with thousands of colors), or a graphic with 24 bits. Digital audio also becomes more realistic at higher bit depths (and of course sample rates).
The first A/D converters were stand-alone units with professional audio inputs. Now A/D converters are built into computers, or accessed through USB or FIREWIRE computer connections. The connection speeds vary, and slower connections can add to the delay caused by converting. The amount of delay (LATENCY) can add up to the same amount of time between playing and hearing sound as was the case in analog audio before the invention of the sync head. To compensate for this, most digital recording software (and hardware) will allow you to directly hear the input of what you are recording.
As sample rates and bit depths increase, Digital Audio will improve in sound until it may rival Analog. Some feel it is already there, but that is still a hotly debated topic.