Audio Analog-to-Digital Converter Performance Specification and Test Method Introduction

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Contents:

  • Normative References
  • Informative References
  • Scope
  • Sources of Information and Inspiration
  • Levels of Device Performance
  • Is Initial Testing and Continual Monitoring Necessary?
  • Framing the Analysis
  • Testing to Refine the Metrics
  • The Test Suite
  • Device Field Testing and Specification Refinement: Background and General Conditions
  • Frequency Response
  • THD+N
  • Dynamic Range (Signal to Noise)
  • Cross-Talk
  • CMRR
  • Intermodulation Distortion (IMD)
  • Amplitude Linearity
  • Spurious Aharmonic Signals
  • Input Overload Behavior
  • Alias Suppression Sync Input Jitter Susceptibility
  • Jitter Transfer Gain
  • Sync Input Lock Range
  • Field Test Summary and Conclusions
  • Appendix: Comparison to TC-04

This document provides an explanatory background to the Federal Agencies Digital Guidelines Initiative (FADGI) Recommendation for metrics and methods pertaining to the performance of audio analog-to-digital converters (ADCs) in preservation reformatting workflows. This introduction is a product of FADGI’s AudioVisual Working Group and in particular the work of the primary consultant on the project, Chris Lacinak of AVPreserve.It begins by framing the group’s approach to determining the recommendations, justifies why initial and continual testing of ADCs is needed and describes field tests undertaken in order to develop the final performance specifications. When relevant, it compares the testing with other professional audio standard approaches (IASA TC-04, AES-17 and IEC guidelines). It then presents the outcomes of testing five different devices and the resulting recommendation per parameter tested. The appendix compares the final list of recommended metrics with those in IASA TC-04.

This introduction is necessary reading for those wishing to understand how the resulting metrics were developed and to understand how they relate to other important standards in the audio engineering field. It provides transparency in the research approach and outcomes as well as a justification for what the working group sees as necessary additions to what was beforehand considered to be the current standard for testing ADCs (IASA TC-04).