Guidelines: Analog-to-digital converters (ADCs): low cost metrics and measurements
Audio-Visual Working Group

Addressing the Need for Affordable Test Equipment

As noted in the discussion of high-level performance metrics and measurement, the highest level of ADC testing requires expensive test equipment (on the order of $20,000 when this research was conducted in 2016) and advanced engineering skills. In order to serve modestly resourced preservation facilities, the Working Group sought a performance-testing approach that reduced both cost and the need for staff with advanced skills. This subsidiary project yielded a description of how to assemble and operate testing equipment with a net cost on the order of $1,500.

The limits inherent in less expensive and less demanding equipment, however, resulted in a testing regimen that is not as broad and precise as that for the high-quality guideline cited above. The high-quality guideline includes 12 metrics, several with very exacting measurements. The low-cost approach is capable of examining 7 metrics, with aim points that make a good fit for affordable test equipment.

Benefits of ADC performance measurement

As reported in the discussion of high-level performance metrics and measurement, the Working Group identified three benefits to performance testing. The first had been anticipated while the second and third emerged from field tests carried out in three federal audio-preservation facilities:

• Benefit 1. Did it pass? How did your ADC perform against the guideline recommendations? Although the low-cost guideline and method does not confirm that an ADC is performing at the highest level, this testing regimen provides partial confirmation and will also identify serious shortfalls in performance.
• Benefit 2. Crosscheck system setup. Equipment and systems may have been incorrectly installed and operators may not be fully attentive. The formality of running the test spotlights problems and motivates corrective action.
• Benefit 3. Ongoing monitoring of ADC performance. Running a test and retaining a report provides a benchmark: run the test again a few weeks later and compare. If something has changed, this finding will motivate further checking and correction if needed.

Guideline for low-cost testing and explanatory reports

Metrics and methods

• Audio Analog-to-Digital Converter Performance Specification and Test Method: Low Cost (PDF, 198 KB). Approved by Working Group, September 30, 2017.

Resources for how to do low cost ADC testing

ADCTest open source software application

Instructions for a test setup encompassing a computer running the Windows operating system and ARTA software installed (http://artalabs.hr/), a user-provided DAC, and an ADC for testing.

• Audio Analog-to-Digital Converter Performance Testing: Low Cost Test Setup User Guide (PDF, 99 KB). Approved by Working Group, September 30, 2017.
• Audio Analog-to-Digital Converter Performance Testing: Template for Recording Results of Low Cost Performance Testing (XLXS, 75 KB). September 30, 2017.

Access to earlier versions of the guideline and planning documents is provided on the archived ADC documents page.

Working Groups

Still Image Working Group
This group is involved in a cooperative effort to develop common digitization guidelines for still image materials.

Audio-Visual Working Group
This group works collaboratively on common and sustainable technical guidelines, methods, and practices for digitized and born digital sound recordings and moving images.