Analog to digital converter

Overview

The term "analog to digital converter" is used to describe a device that accepts analog audio inputs and outputs a digital code that represents the original analog input. This code is typically linear PCM format; but may also be other formats such as DSD or I2S (typically used internally in analog to digital converter units). Once encoded, the information can be stored, transmitted, or copied in a lossless manner. In most instances; further processing is used to generate other formats that employ data compression of both the lossless and lossy variety.

The term can be used to describe the actual analog to digital converter IC or circuit, or an entire unit that incorporates all of the necessary support circuitry to accept line level analog input signals and output the encoded digital audio signal in one or more formats.

For brevity, the term "AD converter" or "AD" will be used interchagably with "analog to digital converter" in the following discussion.

History

Prior to the development of practical digital audio recording systems; AD converters were used in applications such as medical testing and monitoring equipment, and instrumentation (industrial measurement and monitoring). These early converters were limited either by the converter technology at the time or by the amount of data that associated system could handle to much lower resolution than typically used to encode audio. The resolution both in the amplitude domain (typically voltage of the input waveform) and time domain was often quite limited by digital audio standards.

Before storage of the huge amount information generated by CD quality