Tech Notes


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.

Technote 111: Testing USB Headsets (38.01 MB)

This Technote discusses techniques for testing the audio performance of USB headsets using an Audio Precision APx analyzer. Includes APx projects and wave files.

Technote 113: Measuring Sound Pressure Level with APx 1.0.0 (1.20 MB)

Acoustic sounds or noise in the environment is typically measured with a handheld sound level meter. This Technote explains some of the theory behind such measurements, and how to make them instead using an APx analyzer. Using the analyzer adds the capability to perform spectrum analysis, and to visualize the character of the sound signal over time. The latter is especially valuable when measuring non-steady state sounds, such as a pulsating alarm. Requires the APx Sound Level Meter Utility, available as a separate download, to make the measurements.

Technote 114: Measuring Phantom Power (1.12 MB)

Describes how to test microphone preamplifier phantom power, with and without simultaneous audio. You may instead download the APx Phantom Power Measurement Project, which runs the tests (download also includes this Technote).

Technote 115: Measuring Microphone Preamplifier Noise (1.36 MB)

Making noise measurements of microphone preamplifiers (and other high-gain circuits) involves special techniques that differ from those used to measure low-gain devices. This technote explains the theory as well as how to make these measurements.

Technote 116: Testing Smartphones and Tablets (3.53 MB)

Smartphones and tablets provide many ways to route audio. This technote shows you how to make connections and test the sound quality for a variety of these signal paths. Where possible, we will use file-based test signals and recordings to measure the quality of signal paths so that we are not measuring the impairments of multiple paths simultaneously.

Includes the accompanying APx project file. The associated APx Smartphone and Tablet Video Test Files and APx Smartphone and Tablet Audio Test Files may be downloaded separately.

Technote 117: Measuring PDM Microphones and Inputs with APx (2.03 MB)

This Technote has a short review of how PDM works, describe relevant audio tests, looks at the APx PCM module, and conclude with hands-on testing of a PDM MEMS microphone and a PDM microphone input.

Technote 118: Measuring Jitter with J-Test (740.97 KB)

Describes how to use J-test, a special digital test signal which stimulates worse-case jitter over an AES3 or SPDIF digital audio connection. It allows jitter to be measured on an analog output after D/A conversion.

Technote 11: Remote Test Data Retrieval: Send a FAX (257.40 KB)

This Technote describes how to set up the PC that controls System One to be able to automatically send a fax to a designated fax machine with the results, in both tabular and graphical form, of the measured data. The measuring PC can be at a remote unattended location as the fax capability can be configured to operate completely automatically on time, event of data out-of-limits conditions. The description shows how to integrate commercial fax modem cards and software.

Technote 120: Smartphone Audio Test App 2.1 for Android 4-6 (2.08 MB)

This technote describes and explains the use of the APx Smartphone app for Android-based devices, including:

  • How to install the necessary software on the smartphone or tablet device under test (DUT)
  • How to use the Smartphone app on the DUT
  • Which APx projects to use for testing the various signal paths

NOTE: this file is the technote only.

Audio Precision's Smartphone audio test app for Android allows for full testing of audio pathways, including Bluetooth HFP and A2DP, without initiating a call over the network.

Technote 121: Perceptual Audio Testing (1.21 MB)

Technote 121 describes the PESQ and POLQA Perceptual Audio test models, how they are implemented in APx, and when each is appropriate to use.

Technote 121: Perceptual Audio Testing Supplemental Files (3.49 MB)

This ZIP file contains Technote 121 and supplemental material regarding PESQ and POLQA from OPTICOM GmbH.

Technote 123: Measuring Bluetooth A2DP Profile Audio Quality (825.30 KB)

The A2DP Bluetooth® profile is used for high quality music transmission, employing a variety of supported codecs that include MPEG-1, MPEG-2, MPEG-4, AAC, ATRAC, aptX and aptX Low Latency. This technote illustrates how the APx Bluetooth option is used to control and monitor codec selection, measure latency, and test all essential audio parameters such as frequency response and THD+N for Bluetooth-enabled music playback devices.

Technote 124: Measuring ADCs and DACs with the APx555 (2.30 MB)

This Technote explains how to use the APx555 high performance audio analyzer to perform measurements on Analog-to-Digital Converters (A-to-D or ADC) and Digital-to-Analog Converters (D-to-A or DAC). The measurements include those defined in AES17-1998 (r.2009) “AES standard method for digital audio engineering – Measurement of digital audio equipment” published by the Audio Engineering Society and typical measurements specified in data sheets for converter products and converter IC components.

Now provided as a .zip file including APx500 project files.

Technote 125: Using APx to Test Dante-enabled Devices (1.77 MB)

Enabling high-channel count, high-quality audio transport via Ethernet, the Dante protocol is being designed into a growing number of pro-audio products and systems. However, testing Dante-enabled devices can present some unique challenges. Our latest technote delves into this application and walks through two example test scenarios using APx500 Series audio analyzers.

Technote 126: Jitter Testing of PDM Devices (1.21 MB)

This Technote is intended for those involved in design and test of devices with Pulse Density Modulation (PDM) interfaces. It requires an Audio Precision APx analyzer with the APX-PDM option module (model 228), APX-AMC Advanced Master Clock, and APx500 software version 4.2 or later.