AP - The Recognized Standard In Audio Test



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. 



What is ASIO?

ASIO is a PC audio driver technology developed by Steinberg Media Technologies GmbH (and since adopted across the pro-audio industry) that allows audio software to communicate directly with connected audio hardware with extremely low latency, high channel count and bit-transparent transfer of data.

ASIO and PC Audio

ASIO is widely used on Windows-based PCs for professional recording and production because audio interfaces that rely on the native Windows drivers may experience excessive latency and unwanted gain, EQ, distortion and resampling. Using an ASIO driver in a test & measurement situation ensures that it is the performance of the device under test being measured, not the effects of the Windows operating system interfering with the measurements.

ASIO and Audio Interfaces

High quality audio interfaces for PCs now embrace a wide range of digital I/O options and definitions, but nearly all employ ASIO drivers to provide bit-transparent data transfer with low latency to Digital Audio Workstation (DAW) software.

Examples include:

  • USB audio interfaces
  • Firewire audio interfaces
  • High performance PCI and PCIe sound cards
  • MADI sound cards
  • AES/EBU sound cards
  • Virtual interfaces for networked audio

The APx ASIO interface allows you to connect directly to any of these technologies directly on the test PC, allowing for comprehensive testing of audio with no unnecessary components or conversions.


ASIO is standard for the APx555, as well as the APx52x and APx58x Series audio analyzers as part of APx500 v3.1 and higher. The APx515 production test analyzer supports any two channels of ASIO at one time and requires the ASIO software option (SW-ASIO) or the APx515 software bundle 2 (SWB-2).

With ASIO built in to APx500, measurements of ASIO-compliant audio interfaces may now be made directly on the PC running the measurement software, without passing through additional hardware. Note: in order for APx500 to function properly, an APx analyzer must remain attached via USB

Testing PC Audio Interfaces with ASIO

Complete testing of PC Audio Interfaces can now be performed, using signal paths that send or receive audio via USB or Firewire as well as those that employ the analog and digital I/O on the DUT itself. This allows the test environment to closely mirror the "real world" application of the DUTs.

ASIO setup

Virtually any configuration of DUT signal path can be realized and measured. Finally, manufacturers of PC audio interfaces can completely test their devices from end to end.

Comprehensive audio test from the recognized standard

ASIO can be selected for both the analyzer inputs and outputs simultaneously, or ASIO can be paired with any of the other available I/O formats: analog (bal/unbal), AES or S/PDIF digital, Bluetooth, HDMI, or serial digital. Over 30 one-click audio measurements may be made, either individually or in an automated project. Features include weighting filters, and user defined high and low pass filters, 1.2M point FFTs, real-time oscilloscope monitoring, custom reports, statistical calculations, and quasi-anechoic acoustic measurements.

Fast and intuitive UI

APx500 software is the industry standard for clarity, speed and ease of use. Measurements are organized within projects that can be saved, edited and shared. The results browser gives engineers a comprehensive view of all available measurements within a category so that issues can quickly be identified. Absolute and derived results are always available for all datasets.

Automation and sharing data

Complex test sequences can be created within the UI, or the APx API can be accessed for full control from any .NET application or LabVIEW. Graph results are stored within the project, and projects can be locked before sharing with contract manufacturers or other partners.

Rich reports with color graphs and pass/fail results can be generated automatically using default or customized Microsoft Word templates.

Key features

  • Direct connectivity to any PC audio interface with an ASIO driver
  • Complete, interference-free testing of interface characteristics
  • Multiple I/O interface options: PDM, analog balanced/unbalanced, AES3 and S/PDIF digital, HDMI, Bluetooth, and serial digital
  • A flexible, intuitive UI with over 30 one-click audio measurements
  • Powerful “code-free” built-in automation
  • API for VB.NET, C#.NET, MATLAB, or LabVIEW automation and control
  • Custom reports using Microsoft Word templates or output to database
  • Compatible with APx555, APx52x Series, APx58x Series and APx515 Audio Analyzers

  • PC with 2 GHz or faster processor, 2 GB or more RAM
  • Microsoft Windows XP (32-bit, SP 2 or later),Windows Vista (32-bit), Windows 7 (32 or 64-bit)or Windows 8 (32 or 64-bit).
  • 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.

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