Audio Precision APx52xB
Audio Analyzer

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APx525B Series Modular, Two- and four Channel Performance Audio Analyzers

The ideal balance of analog performance and breadth of digital I/O.

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Audio Precision APx52xB Audio Analyzer

The APx525B is a two channel audio analyzer for R&D engineers and production technicians who want fast and easy audio test, but who may not need the ultra-high performance of AP’s APx555 nor require the multichannel capability of the APx585.

Versatility in I/O
APx525B has two balanced and two unbalanced analog inputs and outputs plus 216k digital inputs and outputs via AES/EBU, TOSLINK and SPDIF. APx526B is the four channel version of the APx525B, developed for the 4 channel head units typical of the automotive audio industry.

Additionally, I/O may be expanded with optional Digital Serial (APx525B and APx526B), HDMI + ARC (APx525B), PDM (APx525B and APx526B) and Bluetooth (APx525B and APx526B) modules. Additionally, the optional Advanced Master Clock (AMC) module handles input and output clock signals to synchronize the APx52xB Series with external equipment (or vice versa), and the AMC also enables jitter generation and analysis (in conjunction with Advanced Digital, Digital Serial or PDM modules).

Audio Precision APx52xB Audio Analyzer

Audio Precision APx52xB Audio Analyzer datasheet


High-Performance Options – AG52 and BW52
Developed for power amp designers, the AG52 analog generator option generates exceptionally clean square waves with a rise time better than 2 microseconds and has an improved THD+N of -110 dB (typical). The AG52 generates DIM 100, 30, and B square + sine waveforms and maximum output level is increased from 21.21Vrms to 26.66 Vrms (balanced).

The BW52 ultra-high bandwidth option offers advanced FFT performance: 1.248 million points, DC to 1 MHz bandwidth and full 24-bit resolution. Ideal for Class D amplifier design.

Advanced Digital I/O (option)
Provides AES3, AES/EBU balanced digital I/O on XLR; unbalanced SPDIF digital I/O on BNC; and TOSLINK optical digital I/O. The APx ADIO module enables the generation of advanced impairments for sophisticated test of devices via AES/SPDIF/TOSLINK. It also includes the Advanced Master Clock (AMC) module, which handles input and output clock signals for synchronizing an APx with external equipment (or vice versa). AMC also provides jitter generation and measurement functionality for jitter-enabled I/O modules such as ADIO, DSIO and PDM.

Advanced Master Clock (option)
The AMC module handles input and output clock signals to synchronize the APx52x B Series with external equipment (or vice versa). This module also enables jitter generation and analysis in APx500 Series analyzers with Advanced Digital (ADIO), Digital Serial (DSIO) or PDM modules installed.

ASIO (standard)
PC audio interfaces with installed ASIO drivers appear within the APx500 software as one of APx’s I/O options, with support for up to 16 bidirectional channels. All measurements and test sequences in APx may be used via the ASIO interface, allowing for complete characterization of the connected audio device.

Bluetooth Duo (option)
Audio Precision’s next-generation Bluetooth® module, the APx Bluetooth Duo™, delivers a wider selection of A2DP codecs, faster pair and connection times, an increased feature set within APx500 measurement software, and improved RF shielding for use in production test environments. APx Duo supports Bluetooth core specification v4.2, HFP v1.7, HSP v1.2, AVRCP v1.4 and A2DP v1.3. Note: APx Bluetooth Duo requires v4.5 APx500 software (or later) and can only be installed on “Type E” APx chassis (manufactured after August 2012).

Bluetooth Legacy (option)
APx’s Bluetooth module, with built-in radio and software stack, allows engineers to measure their Bluetooth devices directly. All Bluetooth controls are integrated into the analyzer software and APx supports A2DP, HFP 1.6, and AVRCP profiles. Codec support includes SBC, aptX, CVSD, and wideband speech (mSBC).

PDM 16 (option)
PDM 16 is an optional input module providing sample-accurate inter-channel phase information for up to 16 channels of pulse density modulated signals. With its acoustically-silent remote pod and extension cable preserving PDM signal integrity for up to 10 meters, PDM 16 readily supports MEMS microphone measurements in anechoic chambers. As an added feature, the module can provide up to 50 mA Vdd power supply to the device, or devices, under test.

PDM (option)
The APx PDM option provides direct connectivity for audio devices that have a PDM (pulse density modulation) output such as a MEMS microphone, or an input such as the decimator on a smartphone chip. In addition to standard audio measurements, APx provides variable DC voltage, variable sample rate, and PSR (power supply rejection) measurements for testing devices’ full operating parameters. Jitter capable.

Digital Serial I/O (option)
Digital serial capability is essential in R&D for evaluating designs at the circuit board level. The Digital Serial I/O (DSIO) option provides a direct multichannel connection to chip-level interfaces such as I2S, TDM, and other popular serial interface formats including left-justified, right-justified, and DSP. Jitter capable.

HDMI + ARC (option)
The APx HDMI option allows engineers to measure HDMI audio quality and audio format compatibility on devices such as surround sound receivers, set-top boxes, smartphones, tablets, TVs, and DVD or Blu-ray Disc™ players. APx can stream both lossless and compressed formats from pre-encoded audio test files, making it easy to troubleshoot component compatibility and issues related to downsampling, downmixing, or transcoding.


APx500 software options provide measurements and functionality beyond the core set of capabilities standard for the APx52x B Series analyzers. A variety of options are offered, suited to different specific test applications and requirements. For B Series APx analyzers, and Legacy APx analyzers running version 5.0 software, software option licenses are electronically activated and are tied to a specific analyzer via serial number. For Legacy APx analyzers running APx software version 4.6 or earlier, software option licenses are enabled by one “iButtons” that mount on the rear of the instrument.

Electro-Acoustic Production Test (SW-SPK-PT)
The SW-SPK-PT option enables high-speed production test of electro-acoustic devices, providing key loudspeaker measurements in a single one-second sweep. Results include Rub & Buzz detection, essential Thiele-Small parameters, and impedance magnitude and phase. A proprietary modulated noise measurement is also provided to aid in detecting enclosure air leaks.

Electro-Acoustic R&D (SW-SPK-RD)
The SW-SPK-RD option delivers a complete suite of measurements and results tailored to the needs of designers and engineers developing electro-acoustic audio products. It includes key measurements and results such as complete Thiele-Small characterization; time-gated, quasi-anechoic Acoustic Response; Impedance analysis; plus the Loudspeaker Production Test measurements.

Perceptual Audio Test: POLQA (SW-POLQA-2)
Perceptual audio measurement returns a subjective assessment of speech quality using the next-generation POLQA algorithm for wide-band speech devices or devices with acoustic coupling. (Successor to PESQ with support for HD Voice, 3G, 4G/LTE and VoIP technologies)

Perceptual Audio Test: PESQ (SW-PESQ)
Widely-used, enhanced perceptual measurement for subjective assessment of speech quality on low-bandwidth devices. (PESQ algorithm)

Speech Intelligibility: ABC-MRT Measurement (SW-ABC-MRT)
The APx ABC-MRT plugin is a software option for APx500 audio measurement software that provides speech intelligibility measurement based upon the ABC-MRT speech processing algorithm developed by the Institute for Telecommunication Sciences (ITS) of the United States National Telecommunications and Information Administration (NTIA).

Speech Intelligibility: Speech Transmission Index (SW-STI)
SW-STI is a plug-in for conducting Speech Transmission Index (STI) measurements using the STIPA method.

Sine Frequency Range
0.1 Hz to 80.1 kHz

Frequency Accuracy
2 ppm

IMD Test Signals

Maximum Amplitude (balanced)
21.21 Vrms

Amplitude Accuracy
±0.03 dB

Flatness (20 Hz–20 kHz)
±0.008 dB

Residual THD+N (20 kHz BW)
–105 dB + 1.4 µV
Typically <–108 dB (1 kHz, 2.5 V)
Typically <–110 dB (1 kHz, 2.5 V – option AG52 installed)

Analog Output Configurations
Unbalanced & balanced

Digital Output Sampling Rate
27 kS/s to 200 kS/s
27 kS/s to 108 kS/s Optical

Dolby / dts Generator
Yes (encoded file)

Maximum Rated Input Voltage
230 Vpk

Maximum Bandwidth
>90 kHz
>1 MHz [with BW52]

IMD Measurement Capability

Amplitude Accuracy (1 kHz)
±0.03 dB

Amplitude Flatness (20 Hz–20 kHz)
±0.008 dB

Residual Input Noise (20 kHz BW)
1.3 µV

Residual THD+N (20 kHz BW)
–105 dB + 1.4 µV
Typically <–108 dB (1 kHz, 2.5 V)
Typically <–110 dB (1 kHz, 2.5 V – option AG52 installed)

Individual Harmonic Analyzer

Max FFT Length
1248K points

DC Voltage Measurement

• Microsoft Windows 10, or Windows 8, 64-bit operating systems.

• PC with 2 GHz or faster multi-core processor (2 or more cores)
Note: the Intel Atom dual-core processor does not have sufficient performance to run APx software.

• 2 GB or more RAM (4 GB or more recommended for Windows 8).

• More detailed information is available on our AP Software and Windows Compatibility chart

• Download System Requirements Document

• System performance is sensitive to processor speed; faster processors will yield faster results.

• APx500 is data intensive and it is recommended that other data-intensive applications not be run concurrently. This includes Audio Precision AP2700, APWIN or ATS.