Digital Audio Amplification Reaching Critical Mass?

Although it first appeared as an infant technology more than 20 years ago, digital audio amplification may finally be coming of age. Recent months have seen announcements from several companies, including news of Apogee's DDX technology (see previous report) and Cirrus Logic who recently purchased their Pulse Width Modulation (PWM) digital amplification technology from B&W Loudspeakers (see previous report).

Texas Instruments has also been in the audio news this year with its acquisition of Toccata Technology, developer of the "Equibit" digital audio amplification approach used in products from TacT. At the time of the announcement last March, TI explained that it would be using Toccata's resources to push into the market for "all types of audio equipment, including personal computer speakers, A/V receivers, car stereos, and home theater systems."

TI now appears ready to make good on that promise, announcing this week several new digital audio solutions intended for use by manufacturers building products for the home, car, computer, and portable markets. TI's Niels Anderskouv works with the company's Digital Audio Group, based in Denmark, and says that several major audio manufacturers will be announcing products based on TI's technology as early as spring/summer 2001. In addition, Anderskouv says that TacT will continue to license the Equibit technology for its current and new products.

According to TI, the all-digital audio solution combines the company's newly developed True Digital Audio Amplifier (TDAA) with its digital signal processing (DSP) technology and now preserves the audio signal in a power-efficient digital format from the source to the speaker. TI says that the DSP provides audio filtering and processing, while the company's dedicated Digital Audio Processor performs speaker equalization and correction, tone management, dynamic range compression and expansion, and volume, bass, and treble control.

The new TDAA chipset family is based on the Equibit technology from Toccata, and consists of a TAS5000 pulse-width modulator (PWM) and two TAS5100 H-bridges. TI says that the TAS5000 digital modulator takes I2S, 44.1 to 96kHz and 16- to 24-bit datastreams and processes the incoming Pulse Code Modulation (PCM) data into PWM digital data. The TAS5100 digital power stage is fed by the digital PWM signal directly from the TAS5000 and converts this signal into the desired digital power level at the speaker terminals. TI says that the conversion into an analog signal either takes place in the speaker's voice-coil itself or is done by a simple LC filter.

Anderskouv points out that TI has also been heavily involved with developing the IEEE-1394 (aka FireWire) standard for distributing digital data and sees great opportunity in applying the new TDAA technologies in 1394-based systems. Anderskouv adds that 95% of automobile manufacturers will soon be using 1394 for running digital signals around cars, and that TI's TDAA process is perfectly suited for this application.

As for the high-end digital audio future, Anderskouv hints that TDAA products capable of handling 192kHz/24-bit streams are on the horizon, and that TI is also looking at accommodating Sony's DSD format (currently used for SACD). Clearly TI is trying to bridge as many format gaps as possible—Anderskouv added that "TI's all-digital audio solution establishes a new paradigm in audio reproduction by transferring the high-fidelity experiences of high-end audio systems into the mass market. Recognizing the value and potential of this technology for its customers, TI has realigned its business to have a dedicated focus on the home and PC audio markets."

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