Heads Up: Strong market growth is
The push for better sound quality in smaller packages is sparking a race to develop amplifier chips based on Class D technology, completing the conversion to a digital chain. Vendors are rolling out amps that match the performance of many high-end audiophile components, yet fit into flat panel TVs and other space-constrained applications.
Class D amps have been equated with low quality, but vendors are pushing forward, improving sound quality without reducing positive attributes. "It used to be that for the best audio, you'd use Class A, and for the smallest space you'd use Class D. Now Class D has a combination of advantages, with true audiophile performance and low EMI, along with small size," says Bill Slattery, product line manager at the Analog Semiconductor Components division of Analog Devices Inc.
Class D amps complete the digital processing chain, eliminating the need for a digital to analog converter before the speaker. Beyond that, their central benefit is higher efficiency, which means less heat, so there's less need for bulky heat sinks. For example, Philips Semiconductors says its Class D amplifiers have 80-95 percent efficiency, compared with conventional Class AB amplifiers that convert only 25 percent of their power into amplifying sound. That means the amps can produce eight times the power in the same space as Class AB amplifiers.
Though companies including Texas Instruments, Philips, and STMicroelectronics unveiled chips a few years ago, the market takeoff hasn't yet been great. But that may change.
Digital Decrease: Apogee's Class D
technology provides the final link in a digital pathway, eliminating
components and saving space.
Analysts at Forward Concepts Inc. of Tempe, AZ, call it a "disruptive
technology" that "may eventually replace linear amplifiers in most
audio-frequency applications." Growth in 2003 was an impressive 200 percent, yet
worldwide revenues only reached $84 million. However, revenues should soar to
$823 million by 2008, the company predicts.
Apogee Technology of Norwood, MA, began focusing on this market at the start of the decade, gaining solid acceptance in the home theater market where high wattage systems must fit in fairly small packages. "2004 was a watershed year, the number of engineers who said digital channels did not provide enough performance finally reached the tipping point," says John Gitelman, Marketing Director at Apogee.
That's attracting more players. Analog Devices entered the market late last year with the AD1991, a Sigma Delta modulator that provides feedback. "Closed loop feedback is a key element for performance," Slattery says.