Technical Library


AP Applied: Acoustic Response (936.73 KB)

A look at some of the important features needed in an acoustic audio analyzer, the problems you may encounter in non-ideal testing environment, the needs of good production line testing, and the range of measurements and results that should be produced.

AP Applied: APx Automation with LabVIEW (1.19 MB)

Describes using LabVIEW with APx in a lab or automated production environment. Examples using the APx LabVIEW virtual instrument driver are shown.

AP Applied: Calculating ROI of Audio Test in Production (1.27 MB)

Cost benefit analysis of high performance, low price audio test equipment in production.

AP Applied: Digital Protocol Analysis (1.06 MB)

Explains the various ways to view, measure, and manipulate digital metadata, primarily over the HDMI interface.

AP Applied: Serial Digital Measurements with APx (2.32 MB)

Serial digital signal analysis is essential in research and development for evaluating audio circuit designs at the chip and at the board level. This AP Applied reviews serial testing procedures, and describes the abilities of the DSIO for APx, as well as the PSIA-2722 for the 2700 Series.

AP Applied: Ultra-High Bandwidth Analysis (1.24 MB)

A look at the traditional ways of examining out of band noise signals, as well as the advantages of using an ultra-high bandwidth audio analyzer with full 24 bit FFT resolution from DC to beyond 1 MHz.

AppNote: Headphone Electroacoustic Measurements (1.3 MB)

Due to the close coupling of earphones to the ears and the acoustic transmission paths involved, headphone measurements are complicated.

Our 26-page AppNote discusses these challenges, headphones types, measurement standards, headphone acoustics, acoustic test fixtures required for measuring headphones, and the practical aspects of headphone measurements. Objective measurements are also discussed.

AppNote: SoundWire Audio Testing (1.48 MB)

Audio Precision has teamed up with LnK to provide a complete test solution for SoundWire™ device audio testing that supports both PCM (I2S) and PDM digital formats. This 10-page AppNote provides an overview of this test solution.

SoundWire is a digital audio bus standard developed for the mobile electronics industry by the MIPI Alliance.


Dolby MS11 Compliance Testing with APx500 Series Audio Analyzers (1,023.45 KB)

In collaboration with Dolby engineers, Audio Precision has developed APx-based test solutions, available to Dolby licensees, to support both the Dolby Digital Plus Consumer Decoder SDK and the MS11 Multistream Decoder SDK. In the case of Dolby Digital Plus, compliance testing includes well over 1,200 individual measurements which, if performed manually, could easily take over a week. The APx solution reduces that time to hours. More importantly, because APx generates the test sequence with all appropriate limits, there is no time wasted on recreating a test methodology or deciphering test requirements. Since Dolby MS11 also supports Dolby Digital Plus, this application note primarily focuses on the MS11 SDK test solution.

    130M23 1/4" Array Microphone Data Sheet (1.05 MB)

    The value-priced 130M23 array microphone is an excellent choice for large channel
    count applications, being a cost-effective alternative to higher-end, class-one test and
    measurement microphones.

    2700 Series Datasheet (1.31 MB)

    The 2700 Series is designed for audio engineers who need the highest performance, lowest distortion and greatest flexibility possible in their audio analyzer.

    378M31 1/2" Free-field Microphone Data Sheet (1.14 MB)

    The Audio Precision model 378M31 is a general purpose measurement microphone
    recommended for high accuracy applications where high sensitivity is required for freefield
    response measurements.

    378M32 1/2" Free-field Microphone Data Sheet (918 kb)

    The Audio Precision model 378M32 has a flat response in applications where high
    frequencies (up to 40 kHz) need to be measured very accurately. As an alternative to
    a standard high sensitivity (50 mV/Pa) microphone, it has an enhanced upper dynamic
    range and doesn’t overload or saturate for measurements above 136 dB.

    378M33 1/4" Free-field Microphone Data Sheet (1.8 MB)

    The Audio Precision model 378M33 is recommended for extreme accuracy applications
    where high frequency measurements or high acoustic amplitude measurements
    are required.

    AECM304 Occluded Ear Simulator Data Sheet (1.40 MB)

    The AECM304 occluded ear simulator presents an artificial ear canal to the ear insert,
    approximating the acoustic impedance of a human ear.

    AP Product Catalog (4.96 MB)

    Complete AP Product Catalog. Includes the APx555 , APx52x Series, APx58x Series, APx515, 2700 Series ATS-1, APx500 software and accessories.

    APx Bluetooth Option Datasheet (657.66 KB)

    The APx Bluetooth® option is the best solution in the world for testing audio over Bluetooth wireless technology. No other analyzer combines integrated Bluetooth controls with APx’s best in class speed, ease-of-use, and performance.

    APx Digital Serial I/O Datasheet (867.61 KB)

    Audio Precision's new Digital Serial I/O for APx audio analyzers provides multichannel, chip-level connectivity for designers of HDMI receiver/ transmitter chips, converters and other micro-components. Innovations include 8 channels of simultaneous audio data, independent clocks, buffered oscilloscope monitors, and built-in support for left or right justified, I2S and DSP formats.

    Technote 001a: Generating Impedance vs. Frequency Plots with APWIN (98.97 KB)

    This Technote is a rewrite of Technote #1 to support System One and System Two using Windows APWIN software. An additional method using an external amplifier and current sense resistor is provided.

    Technote 101: LabVIEW ActiveX Automation for System Two / 2700 Series (1.16 MB)

    TechNote 101 describes the basic principles and techniques needed to operate System Two / 2700 Series instruments using the Audio Precision control software as an Active X automation server within the LabVIEW environment. Although it is possible for LabVIEW to directly control GPIB versions of Audio Precision instruments, GPIB control of Audio Precision systems is not the subject of this TechNote. Instead, TechNote 101 deals with the capability of LabVIEW to control the standard APIB versions of Audio Precision PC-controlled instruments via the instrument control software, using Microsoft ActiveX automation.

    Technote 102: Using Audio Precision High Speed Tester (HST) (28.09 MB)

    The AP High Speed Tester (HST) application was originally developed to test playback only devices on the production line. The objective was a fast, accurate and easy-to-operate test station with a limited graphical user interface that just indicated the test results and had the ability to save results to a log file.

    In addition testing play-back devices, HST 2.0 can use the instrument's generator to drive the input of the device under test. Both input and output can be set to digital or analog, and limits, user prompts and sample rate can be defined easily via a new setup utility.

    This flexibility allows HST 2.0 to test almost any type of audio device - amplifiers, DACs, ADCs, signal processors, MP3 / DVD players etc. - quickly and easily.

    Technote 104: Introduction to the Six Basic Audio Measurements (1.19 MB)

    Technote 104 discusses methods of making a set of basic measurements using an Audio Precision 2700 Series or ATS-2 audio analyzer.These are Level, Frequency Response, THD+N, Phase, Crosstalk, and Signal-to-Noise Ratio

    Technote 105: FM Radio Receiver Testing with APx Audio Analyzers (1.54 MB)

    In this technote, we discuss how to test the analog sound quality of FM radio receivers using an Audio Precision APx500 Series audio analyzer. We also discuss how to test the Radio Data System (RDS), which allows text, such as song title and artist, to be transmitted digitally as part of the analog radio signal.

    Technote 106: Measuring PSRR (Power Supply Rejection Ratio) (1.16 MB)

    In this technote we describe and compare two different methods to measure PSRR. Then we give instructions for using the APx PSRR Measurement Utility, which simplifies the calculations and graphing on APx analyzers.

    This technote is included in the APx PSRR Measurement Utility download.

    Technote 107: Measuring the Sound Pressure Level of Portable Audio Player Headphones (1.27 MB)

    Describes how to measure the sound pressure level developed by portable audio players and their associated headphones, according to British Standard / European Norm 50332. Also shown is how to use the APx Portable Audio Player / Portable Headphone Test Utility to facilitate making the necessary measurements with an APx500 analyzer.

    Performing the described tests requires that you download the APx Portable Audio Player / Headphone Test Utility. This Technote is also included in that download.

    Technote 108: PC Audio Testing (20.51 MB)

    This Technote discusses the techniques necessary to perform the "Basic Six" audio measurements on consumer-level PC audio devices. This category includes sound systems integrated into notebooks, netbooks, tablets, and PC motherboards, as well as expansion cards and some external devices. It doesn'€™t include USB-connected headsets, nor pro-audio devices with balanced input and output connections.

    Includes APx project and .wav test signal files for playback.

    Technote 10: SWR-122 Series Switchers APIB Interface Description (64.35 KB)

    System One SWR series switchers are normally controlled via the APIB interface and S1.exe software. This Technote describes the APIB interface used on the switchers and explains how to control them from a generalized parallel port. A sample BASIC program is included to program the switchers from a PC parallel printer port. This Technote assumes programming and hardware knowledge.

    Technote 110: Legacy Instrument Migration to APx (1.81 MB)

    Addresses conversion of tests and procedures/macros written using AP'€™s Windows-based APWin, AP2700, or ATS software to APx500. If you are using AP'€™s DOS-based S1.EXE software for System One, please refer to Technote 109 instead.

    130M23 1/4" Array Microphone Full Specifications (129 kb)

    Full specifications for the 130M23 1/4" Array Microphone.

    2700 Series Full Specifications (1.59 MB)

    2700 Series Full Specifications

    AP specifications in hard copy booklets & brochures can be out of date. The specifications documents available for download from our Web site have the most current and correct information. If there is a conflict between printed and online specifications, the online version is the prevailing document.

    2700 Series Getting Started Guide (5.9 MB)

    Getting Started With Your 2700 Series Instrument


    2700 Series User Manual (8.43 MB)

    2700 Series User Manual

    378M31 1/2" Free-field Microphone Full Specifications (133 kb)

    Full specifications for the 378M31 1/2" free-field microphone system.

    378M32 1/2" Free-field Microphone Full Specifications (138 kb)

    Full specifications for the 378M32 1/2" free-field microphone system.

    378M33 1/4" Free-field Microphone Full Specifications (138 kb)

    Full specifications for the 378M33 1/4" free-field microphone system.

    AP Basic Extensions Manual for the ATS-2 (1.59 MB)

    AP Basic Extensions Reference for ATS-2

    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.