Audio.TST Archive

The other good news was people's positive reaction to v1.1 of the APx software. We saw a lot of nodding heads when we talked about the need for easy Dolby/DTS confidence testing. There was also an ongoing discussion at the booth on the dividing line between those who need the flexibility and performance of the 2700 Series or ATS-2 versus the simplicity and speed of the APx.

Read on in this issue for some background on audio fidelity in Windows Vista, take a closer look at testing playback-only devices, and talk with Jim Duncan, AP's longest-term employee and Senior Service Manager.

Bruce

Testing playback only devices with APx: a new approach to "external sweep"

Playback-only devices have always been a challenge for audio testers. With no input to receive a generated stimulus signal, measurements have to be taken from an independent tone played back on the device under test. With traditional audio analyzers such as the SYS-2722, playback-only devices are characterized by having the analyzer measure two parameters, with one being the independent (x-axis) variable, and the other the dependent (y-axis) variable. For example, the frequency and level of a tone are measured and plotted on a graph, with frequency on the x-axis and level on the y-axis. This gives you a frequency response measurement. This approach allows for maximum flexibility in creating custom measurements; however it does create a dependency on the stimulus signal, and actual set-up of each measurement can be very complicated.	Frequency sweep in AP2700
Creating the measurement requires the user to describe the stimulus tone and adjust settings in several panels, for example telling the analyzer how to know when to take a measurement. Then if the signal sweeps too quickly, the analyzer may miss a data point while the device under test is settling. Calculating THD+N or other measurements requires another completely different setup and a rerun of the measurement.
Easier test with the APx The APx585 solves these problems by providing a list of known measurements and specifying the stimulus tone. The analyzer is listening for a known signal, so it's closer to a closed loop test with an on-board tone generator. Setup of a playback-only sweep is reduced to just a few seconds: Select the measurement (for example "Stepped frequency sweep") from the Measurement Navigator Play the specified tone on the device under test Click Start Because the APx knows what to expect, settling parameters are optimized and the software knows if it missed a point. Of course, different tests require different signals, so the APx Reference CD contains several tones and sweeps with varying numbers of points and levels. From a single sweep, level, phase, deviation, frequency response, and THD+N are all calculated and graphed ready for export or further analysis.	Frequency sweep in APx
For the power user, nothing matches the 2700 Series in terms of flexibility and performance, but for the vast majority of test, this faster and easier approach to testing playback-only devices is proving very popular. In addition to measuring playback-only devices, the APx now has Dolby/DTS confidence tests. Download the v1.1 beta software and run in demo mode to see how easy it is, or contact your AP Sales Partner for an on-site demonstration.

Audio Fidelity in Microsoft Vista Logo testing

Last month, we announced that Microsoft had specified the SYS-2722 as the official audio analyzer required for the Audio Fidelity tests for the Windows Vista Logo Program. Audio.TST spoke with Steve Peterson of ATECS, the AP Sales Partner for the Northwest of the USA (including the Microsoft campus in Redmond, Washington). Steve has become AP's resident expert on Microsoft Audio Fidelity tests.

How did AP get involved with Microsoft audio requirements?

AP has a long history with Microsoft. In the late 1990's Microsoft & Intel developed a performance specification called PC-99. It had requirements in all areas of PC performance -- including audio. Many of those audio performance requirements were tested with System Two test files.

Audio Precision got involved when it became clear that with our expertise in audio test, we could contribute to the development of a standard testing procedure for defining and measuring audio performance in PCs. This resulted in the Personal Computer Audio Quality Measurement (PCAQM) document referred to in chapter 17 of PC-99, with contributions from Audio Precision, Compaq, Crystal Semiconductor, Intel, and Microsoft. The net result was better audio all around, so everyone was a winner.

What can we expect from Vista Audio Fidelity Requirements?

Microsoft has defined very strict requirements for its Vista Logo Program, and that means audio fidelity must meet higher performance standards than in the past.

When designing the requirements for Vista, Microsoft's goal was to radically improve PC audio. Before Vista, audio performance was not consistent and many vendors weren't testing audio as recommended. Then Intel introduced their High Definition Audio standard in 2004 with its 8 channel, 24 bit, 96/192 kHz audio and that really changed the game.

Microsoft's new Universal Audio Architecture or UAA raises the bar for audio quality, ensuring that audio performance is consistent and that Windows Vista takes full advantage of improved hardware capabilities. With Vista, audio performance must meet the audio fidelity requirements for the device to carry the Vista Logo.

Why isn't the ATS-2 able to perform the tests?

The short answer is because Microsoft developed their Driver Test Manager or DTM audio fidelity tests only for the SYS-2722, the recognized standard in audio test. The ATS-2 may not provide sufficient performance or features for future Windows Logo requirements.

Who needs to know about Vista Logo Program Audio Fidelity?

Anyone who wants a Vista logo! That means vendors who provide codec parts, USB audio devices, motherboards, video conferencing equipment, USB headsets, anything.

One important fact to keep in mind is that every SKU, i.e. every different model or configuration of a product, must pass tests independently. Even if you change the layout of audio cables inside the PC, the whole battery of tests has to be rerun because the new layout may change the audio quality.

How complicated is Vista Audio Fidelity Testing ?

There's definitely a learning curve. The test set up requires three PCs all networked together: a DTM Controller PC, a client PC running Vista, and a PC running AP2700 software to control the SYS-2722, all synchronized though Microsoft's DTM software. Getting everything connected, and then becoming familiar with the operation can take some time. Once it's all set up, running audio fidelity tests is straightforward. Passing the tests is another matter.

The good news is Microsoft recognizes the learning curve, so enforcement of the audio fidelity requirement doesn't start until June 2007. That gives everyone time to become familiar with the tests and correct hardware or software design flaws, so when the requirements are enforced there will be a high level of confidence that a PC will pass.

The bottom line is: start audio fidelity testing now to be ready with high quality audio performance before next summer.

The SYS-2722A-M is a specially configured 2722 with all the required filters and cables as specified by Microsoft for the Vista Logo Program Audio Fidelity Tests. For more information, please contact your local AP Sales Partner.

To read more about the Vista Logo Program Audio Fidelity requirements, visit the AP website's Audio Fidelity Testing for Windows Vista Logo page: www.ap.com/windowsaudiotest

News

APx585 wins Pro Audio Review "Best Audio Test Equipment 2006"

At AES earlier this month, Pro Audio Review announced that the APx585 won the first prize in the PAR Excellence 2006 Awards in the Test & Measurement Equipment category. Look out for the APx in the November and December issues of Pro Audio Review.

Meet AP: Jim Duncan, Senior Service Manager

AP's third hire, Jim Duncan started in 1984. There's very little he doesn't know about audio analyzers.

What's your specialty here at AP?

I started off as a manufacturing tech on the production line, but now as the service manager I deal with customers most of the day. I spend a lot of the time diagnosing problems over the phone or email to determine whether they need to send the unit back to the factory.

A lot of people want to make repairs themselves. I can usually tell from a Performance Check whether the job is manageable or whether they need to send it in. Sometimes I can tell from a photo of the display: like if someone hears a buzzing, and I can see the input termination is enabled, chances are the input was over 32 volts and the protection circuit kicked in. 

What's your best contribution to AP over the years?

I'm most proud of the work we did training the AP Sales Partners to offer maintenance and service out in the field. We set up a communications network so they knew who I was and I was able to get out there and meet them in their location, see what kind of tools they have. Sometimes an oscilloscope and a soldering iron just won't cut it. It's been some work, but it's worth it. Performance checks have become my best friend. 

Do the engineers ever come to you for product development input?

Engineers quiz me for quality control to find weak spots. I enjoy working with them to improve the new APx product. And I helped get the Portable One display lens changed to acrylic rather than glass. Acrylic is much stronger and we designed the replacement to just pop out, which makes servicing a lot easier. 

Are you working on any interesting side-projects?

Yes. The AP Museum. I'm trying to put together a collection of every instrument AP has ever released. I have everything from 1989 onwards, though sometimes it's been a case of taking a test unit that Engineering has been experimenting on and downgrading it back to its original form. And I found the System One Serial Number 4, the first true AP audio analyzer. Numbers 1 through 3 were prototypes. I have Number 5 at home - and it still works !

What do you do for fun? Any audio-related hobbies?

Right now I'm working on transferring an audio history of family stories from DAT to PC. Just goes to show you can never know which format is going to survive. Other than that it's more leisure time, hiking, camping. I recently did Larch Mountain in the Columbia River Gorge.

Next time you have a service question, chances are Jim will be involved. You can contact Service anytime by emailing service@ap.com

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