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.
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.
An in-depth look at the behaviors of decoupling schemes in power supply designs for audio.
Fast Audio-Band Measurement Using Log-Swept Chirp Signals by Dr. Tom Kite, AP VP of Engineering
Characterizing professional and consumer audio equipment requires techniques which often differ from those used to characterize other types of equipment. Sometimes this is due to the higher performance requirements. Other times it is due to the peculiarities of the audio industry. Other fields deal with some of the same measurements as those in audio. From level and THD to jitter and noise modulation, no other field has the breadth of requirements found in high performance audio.
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.
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
Transmitting and storing audio signals in the digital domain is well-established in the broadcast industry. Analog audio has given way to the AES3 and Sony/Philips Digital Interface Format (SPDIF). AES3 data streams are also embedded in SDI television signals. Handling audio in the digital do- main offers many advantages over analog methods. An analog signal incurs progressive degradation as it passes through a chain of circuits. Converting the analog signal into digital and converting back to analog as late in the chain as possible overcomes this degradation.
Measuring Distortion in Switching Amplifiers by Bruce Hofer
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.
The Personal Computer audio environment has evolved over the years to become a significant entity within the field of acquisition and rendering of audio information. The personal computer is a highly sophisticated interactive environment that is much more complex than a conventional dedicated home audio device, leading to new problem areas. These include, but are not limited to, stochastic interrupts, network accesses, disc I/O and disparate hardware qualities. While the environment of a highly matrixed multi-tasking concurrent operating system offers many opportunities to overcome quality issues, the PC, due to the media-rich tools and feature sets, is becoming the entertainment capture and rendering device of choice for future generations. Presented at the 114th Convention, 2003 March 22–25 Amsterdam, The Netherlands. Wayne Jones, Michael Wolfe, Theodore C. Tanner Jr., Daniel Dinu
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.