Beaverton, Oregon—If you're developing a multi-channel audio product such as a Dolby 7.1 Surround Sound or automotive sound system, here's news of a PC-controlled tester from Audio Precision, Inc. that will let even semi-skilled operators get up-and-running quickly. Its liberal use of colorful 3-D graphics makes it a snap to learn and use.
Slated for availability this July, the APx585 audio analyzer will work in conjunction with a fast Windows PC. As an almost plug-and-play box, the APx585 will also feature a Windows user-interface that lets new users take measurements almost immediately.
Communicating with a PC across a 480-Mbit/s USB 2.0 (Universal Serial Bus) connection, the Model APx585 analyzer will accommodate both balanced and unbalanced I/O, with eight low-crosstalk simultaneously-operable inputs and eight outputs. The analyzer’s inputs also auto-range, making operation with unknown signal levels rather straightforward.
Both BNC coaxial cable connectors and DB-25-type connectors are located on the unit’s front panel.
Finally, you’ll also get two channels of SPDIF-EIAJ per IEC60958-compatible digital I/O.
Automated Sequences
Audio Precision’s latest analyzer will also be able to automate test sequences—without ever writing a single line of code.
Automating test sequences can save development time, and make for a seamless transition from the lab onto a production line. On the factory floor, where workers may be semi-skilled or even totally unfamiliar with test gear, automated test sequences are de rigueur. More on this in a moment.
On-Screen Checkbox
In a pre-release demo I witnessed at eeProductCenter, the APx585's tree-style user interface, dubbed the measurement Navigator, revealed that the instrument can make a broad set of measurements. After a 20-minute warm-up, it was ready for use.
Using an on-screen checkbox, then clicking on Run, lets an entire test sequence be defined (by selecting multiple tests). Then all you need do is click the Navigator's Run button to let the instrument make the selected measurements. Settings such as frequency range and voltage level are located next to the display of test results, so you can make changes and run a test again rather quickly.
Running Sequences
As mentioned above, selecting a variety of different measurements and running them sequentially can also be done. To do that, you check on-screen boxes next to the measurements you want to make, then click the system’s Run button. The sequence is then run automatically. If you wish, you can then modify your settings and repeat the whole sequence very quickly, without fussing.
When you run a sequence, you can also set Pass/Fail limits. The APx585 has many options for creating limits, and you can actually draw them right on a display of the measurement results. Alternatively, you can map measurement results into a limit grid, and ultimately get editable limit curves. You can also create your own custom limit curves by specifying numeric values as upper or lower limits at different frequencies.
In operation, measurements are marked with Pass or Fail icons in the Navigator, and measurements that exceed limits are flagged.
You can also use the Navigator to run multiple sequences of measurements on different signal paths. You can even select combinations of analog and digital signal paths, and define values for settings such as voltage levels. You can also select the measurements you wish to make on each path.
Integrated Reporting
The test sequences run on the APx585 are also supported with an integrated reporting facility. It generates graphic reports on individual test settings and results every time a sequence is run.
Reports include the parameters for each test setup, and a graphical display. The reports also show numeric test results. Moreover, each channel and each test can be flagged if a limit was exceeded.
Reports are generated in HTML format, and are also exportable into other popular Windows applications.
Project Files
What's more, collaboration among project design teams can be expedited using the APx585's project file structure. Measurement settings and automated sequences are saved in a project file, which can be loaded and immediately run by another APx585 user. This enables test results to be quickly reviewed and analyzed independently by different team members.
Confidence Testing
Especially significant is that Dolby and DTS (Digital Theatre Systems) so-called projects are shipped with the APx585. The DTS and Dolby files give designers of audio systems that conform to these standards a way to assess readiness for Dolby and DTS certification.
Dolby Digital 5.1, for example, implements discrete channel soundtracks encoded to an AC-3-compatible bitstream so that sound can be heard through five main speakers and a sub-woofer. Each speaker is independent of the others and uses its own track.
Dolby Equivalent
The projects use measurements developed by Audio Precision that are the equivalent of those used by Dolby and DTS. Also included is a family of multi-tone IMD (intermodulation distortion) measurements, including standard DFD, MOD, and SMPTE types.
When you load these projects and click Run in the APx585's measurement Navigator, all appropriate measurements are made and a report is generated. The reports also contain information about signal paths, measurements, settings, Limits, and sequences. All are saved in a project file.
Now, if the project file is routed to other team members, and then loaded into another APx585, the Navigator is automatically configured with everything to make the identical measurements you made. Or, a co-worker can run your entire automated test sequence.
Ultra-Fast Sweeps
The APx585 also uses a patent-pending sweep method Audio Precision dubs continuous sweep. The continuous sweep operation is claimed to be much faster than previous approaches, and I've seen it in operation. It is indeed lightning fast.
Audio Precision's continuous sweep mode can also make multiple measurements at once. A typical 1-second sweep, for example, with a subsequent ten seconds or so of PC processing time, results in up to 14 measurements of characteristics such as frequency response, THD (total harmonic distortion), crosstalk, group delay, and more. Wow. The amount of information gleaned from the data of a single sweep is awe-inspiring.
The screen image shown below is that of an 8-channel THD+N measurement (on colored meter bars). Pull-off signal monitors provide both oscilloscope and spectral views. The Measurement Navigator/Sequencer is at the left.
Click to view Windows screen image
The APx585 also provides a measurement Selector that displays thumbnails of all these measurements. This selector can be clicked under Windows to display in a full-screen mode.
Other tools available in the APx585 include realtime input-signal monitors, and a general-purpose FFT (fast Fourier transform) spectrum analyzer.
Scope And Spectral Views
For its part, the input-signal monitors provide a choice of a realtime oscilloscope view and an FFT spectrum view. The instrument's FFT tool provides both time-domain and frequency-domain views, with an FFT acquisition variable of up to one million points.
You can also use the input-signal monitors to provide level, frequency, and THD+N (THD plus noise) meter readings. All of these meters display all eight channels, and any number of them can be viewed in realtime while the APx585 is making measurements.
Click to view scfeen image
The screen image above shows an 8-channel frequency response measurement on the system’s 3-D graph. The Selector filmstrip of small box views at the bottom can show as many as 14 thumbnail views. These can be ready for full-screen expansion at the click of your mouse button.
Hardware Specs
Let’s look at some hardware specs. The box operates at a sampling rate of 192-kHz, and exhibits a bandwidth that extends from DC out to 80-kHz-plus. The system is quiet, too, with a -102-dB of residual THD+N, and just 1.3-µV of residual input noise.
On the output side, the APx585 generates signals ranging from 2.5-µV to 14.4-V (rms, balanced) over a range extending from 5-Hz to 80-kHz, with 3-ppm frequency accuracy. Each channel can deliver up greater than 30-mA peak.
Options
There are also some options for the APx585 that can make life simpler. These include a APx581 8-channel switching amplifier measurement filter (shown here) for testing switch-mode amplifiers such as Class-D types.
The filter controls high slew-rate signals and out-of-band noise that’s common in switch-mode power amplifiers. This filter is priced at $3,000.
An optional $800 CAB585 cable kit provides a set of cables for connecting the APx585 to a test device, with cables harnessed and color-coded to simplify the task of connecting up to eight channels.
A $1500 2-year extended warranty, which adds two years to the company's standard 3-year warranty is also available. Annual factory adjustment is also available.
A Dramatic Change
"We've seen a dramatic change from audio experts to engineers who have little formal audio training," Audio Precision co-founder and chairman Bruce Hofer mentioned in a recent interview. "For these people, designing products such as PCs and portable media players, the 585 can be a productivity tool."
Hofer says his APx585 will be available in July, priced at about $21,000. Computed on a per-channel basis, that's quite cost-effective.
The Dolby and DTS projects will be shipped as a free upgrade by the end of the year.
Want to know more? Contact Tom Williams at Tech Support, Audio Precision, 5750 S.W. Arctic Dr., Beaverton, Oregon 97005. Phone: 800-231-7350 or 503-627-0832. Fax: 503-641-8906. E-mail: techsupport@ap.com or tomw@ap.com
Audio Precision, 503-627-0832, www.ap.com
