White Papers & Books


Appnote 5: Measurement Techniques for Digital Audio (Julian Dunn) (2.94 MB)

This book by the late Julian Dunn examines in great detail techniques for evaluating the performance of converters and digital interfaces.

Includes a full set of AP2700 macros and tests that accompany the text.

APx PDM Option Technical Details (389.22 KB)

Document describes in detail the features and operation of the APx PDM module. The module is an available option for the APx555, APx52x Series and APx58x Series Audio Analyzers.

Building Analog in the 2010s (1.37 MB)

Slide presentation (in PDF format) given by AP Chairman Bruce Hofer at the 131st AES (Audio Engineering Society) convention in New York City in 2011. Bruce'€™s presentation draws from 30+ years of experience to focus in-depth on five select topics: Models of non-linearity, passive component quality (“perhaps one of the most significant factors in analog design”), op-amp selection, noise in analog circuits, and circuit layout considerations.

Class D and Linear Power Amplifier Testing (2.32 MB)

Joe Begin's presentation given at AES Brazil 2012

Designing for Ultra-Low THD+N (6.13 MB)

Bruce Hofer describes some of the lesser known phenomena that can make the difference between a truly great and a merely good analog design, and offers examples of estimates of noise and distortion due to these effects. This article was originally released in two installments in the publication AudioXPress. We wish to thank editor Joao Martins for his kind assistance and support for Audio Precision.

Fundamentals of Audio Test (2.58 MB)

Tom William's presentation at AES Brazil 2012

How to Write (and Read) Audio Specifications (404.34 KB)

Discusses writing and reading good audio specifications. Guidelines are provided, then key specifications for two classes of audio device are examined for correct expression and form, with examples of real-world specs for comparison.

Limitations in making audio bandwidth measurements in the presence of out of band noise (72.26 KB)

Audio analyzers are optimized to make high quality measurements up through their maximum specified bandwidths. The presence of significant energy above these bandwidths can have a profound effect on the audio measurements and possibly induce errors. This white paper provides valuable information on avoiding the possibility of errors when testing digital to analog converters and other audio devices that contain significant energy above the audio band. Written by Bruce Hofer

Measuring Switch-mode Power Amplifiers (1.80 MB)

Switch-mode audio power amplifiers are becoming increasingly popular due to their smaller size, lower weight, and improved efficiency. Their advantages are obvious in low power battery operated personal audio players and laptop computers. However they are also progressively displacing more traditional linear designs in mainstream applications such as home entertainment systems, automotive sound systems, and professional installations where high quality audio is important. Measuring the performance of switch-mode amplifiers presents some new and unique challenges. They inherently generate ultra-sonic artifacts and spurious signals with slew rates that can provoke non-linear behavior within the input stages of high quality audio test and measurement equipment. Absolutely worthless and inaccurate results can result unless effective measures are taken to prevent this non-linear behavior. Written by Bruce Hofer.

Testing Broadcast Audio Consoles (143.14 KB)

Describes the importance of a comprehensive audio console (mixer) testing and repair program in the broadcast field. Includes recommended tests and procedures.

The Audio Measurement Handbook (1.60 MB)

This reference handbook is a practical, hands-on guide for workers in all phases of the audio field. It covers basic tools and techniques, common environments for audio testing, application of these techniques to common audio devices, the typical ranges of performance to expect in different devices, and a glossary of terms and key specifications used in audio measurement. 178 pages Written by Bob Metzler.

Understanding PDM Digital Audio (621.03 KB)

by Dr Tom Kite, AP's VP of Engineering.