How new products challenge audio test

An exclusive interview with a technical leader

By Larry Maloney, Contributing Editor -- Test & Measurement World, 6/1/2010 12:00:00 AM

BRUCE HOFER Chairman and Co-founder Audio Precision Beaverton, OR Bruce Hofer co-founded Audio Precision in 1984 with a group of audio engineers from the labs of Tektronix. In addition to serving as board chair, Hofer remains technically active as the company's principal analog design engineer. He has received 13 patents, authored many articles and papers, and in 1995 received the Fellowship Award from the International Audio Engineering Society. Hofer earned his BSEE degree from Oregon State University in 1970. Contributing editor Larry Maloney conducted a phone interview with Bruce Hofer on changes in the audio test field brought on by the expanding variety of consumer electronic products Read the continuation of this interview. Read past Viewpoint columns at www.tmworld.com/viewpoint

Q: What are the biggest changes in audio test since your company was founded?
A: The biggest change has been the move from analog to digital storage. When we started in 1984, LP records were still the most popular form of serious music. But about the same time, the compact disc and the personal computer were also coming onto the scene. Both caused profound changes in audio test. For example, the PC soon became a powerful force as a test-instrument controller, replacing expensive HP-IB or GPIB-based testers that often required a software engineer for programming. At Audio Precision, we immediately seized on the PC and made it a part of our product offering. By embracing the PC, I believe Audio Precision led the way in automating audio test.

Q: What are Audio Precision's fastest-growing applications?
A: Testing for HDMI (high-definition multi-media interfaces), Dolby, and DTS (digital theater systems). These applications are being driven by multichannel sound, typically five- to seven-channel, surround-sound systems. Consumer devices have embraced HDMI as a virtual standard interface. We've gotten heavily involved not so much in testing the HDMI interface itself, but in analyzing how audio passes through the interface and appears on a device that reproduces the sound or, conversely, in analyzing how a device that is recording the sound or taking it from another source encodes it and puts it onto the HDMI bus.

Q: How are you changing your equipment to meet the needs of customers who do not have strong backgrounds in audio test?
A: It all starts with the user interface, which has changed significantly from our past products. Earlier products were very hardware-centric and designed for audio engineers who really understood audio measurements. So, you got multiple panels for controlling the signal generator, analyzer, sweep engine, and various options. In contrast, our newer products are much more measurement- or result-oriented. When you use our new APx family, the first thing you do is indicate what you want to measure, such as signal-to-noise ratio, and the instrument automatically sets up and performs the test. This easy-to-use interface is especially important, as our testers get used by engineers all around the world.

Q: What has been your most significant product introduction of the past year?
A: It is actually an option, called the BW52, which adds a faster ADC to our APx520 family of analyzers. This option extends the analyzer's capability from 90 kHz to 1 MHz. This allows you to see the full spectrum of the signal. What is driving the need for this option is the growth in class D power amplifiers, which switch at frequencies of 200 to 300 kHz. R&D engineers need to see what that switching frequency is and how much of it is in the signal, as well as how you modulate switches to minimize distortion. One of the applications we're targeting for this new option is automotive, where most of the multichannel power amplifiers are class D. Still another key application is converter testing.

Q: How about major product announcements for 2010?
A: At the recent Audio Engineering Society show in London, we introduced the APx515, a two-channel audio analyzer for production test. We put a big focus on value engineering so we could offer a product that sells for thousands less than our lowest-priced analyzer. Target applications include power amplifiers and home theater products. Although most of our testers are used in product development and quality assurance, we expect the APx515 will trigger more growth in our production test business.