Longtime leading supplier of high-performance audio processing technology for professional and premium consumer applications, Analog Devices, Inc. introduced a new digital audio processor designed to bring a rich acoustic experience to cost-conscious consumers of automotive and home stereo systems. While audio sources, such as CD and MiniDisc, have all converted to digital media by now, the technology used in audio processing has remained primarily analog based. This new development from Analog Devices represents a major milestone in the migration from the analog to the digital domain for audio processing.

The first member of the ADI's SigmaDSP family of digital audio processors combines high-performance, 112 dB, digital-to-analog converters (DACs) with a digital signal processor (DSP) optimized to execute audio algorithms. Customers have embraced the sound quality and the ease with which the digital audio processor can be configured using a Microsoft Windows-compatible graphical user interface (GUI) provided by ADI.

The premier member of ADI's SigmaDSP family, the AD1954, alters the landscape for audio system designers, who have traditionally relied upon all-analog solutions to keep costs low. Featuring a high-quality digital audio processing engine configured through an intuitive GUI, the AD1954 SigmaDSP simplifies the digital development process by not requiring any DSP programming expertise and thereby speeds time-to-market. The AD1954 provides a rich feature set that improves the sound quality of speakers and eliminates high-volume distortion, thus satisfying the demands of customers who want an optimal audio system at the best possible price.

"The AD1954 SigmaDSP is an alternative to a fully programmable DSP or all-analog solution," said Patrick O'Doherty, product line director, Digital Audio Group, Analog Devices. "This first SigmaDSP solution both demystifies DSP development for the analog designer and makes affordable the addition of DSP functionality to a wide range of automotive stereos and to the entire spectrum of home stereo systems."

About the AD1954 SigmaDSP Digital Audio Processor

The AD1954 solves the essential problem of integrating high-performance audio converters with a DSP optimized for audio processing on a single chip, thereby allowing the signal to remain entirely digital from the audio source to the system output. Key features include: 3 channels of digital audio; a 7-band, 48-bit stereo equalizer; delays for loudspeaker location adjustment; Phat Stereoý spatial enhancement; and a dual-band, professional-quality dynamic processor. Its three DACs achieve 112dB signal-to-noise ratio (SNR) at 48 kHz. Its dynamic processing features include:

• Fine-tuned bass boost to enhance low frequencies for small loudspeakers
• Algorithms that virtually increase loudness by removing distortion at high volumes
• Midnight mode which automatically reduces loudness in high-volume instances (e.g., sudden loud scenes on DVDs)
• Low-level expansion to lift low-volume signals above road noise (for car stereos)

Analog Devices, Inc 804 Woburn Street Wilmington, MA 01887. Tel: 800-ANALOGD (800-283-5643), Fax: 781-937-1021. http://www.analog.com/

Although digital audio has been with us for some time, it has not been completely digital. For example, the majority of systems out there, including mini component systems, small radios, and car audio systems, are still analog processing based. The SigmaDSP audio processor technology from Analog Devices helps bridge the gap between the analog and digital worlds. It integrates a sophisticated DSP engine with on-chip converters offering a performance level of 110 dB signal to noise. This chip isn't the only integrated solution but it is the only one that performs at such an impressive performance level. Analog Devices didn't stop there with the integrated solution, they also addressed programming needs with a graphical users interface (GUI) designed for the non-gurus of DSP to be able to program the chip.

The company is targeting PC multimedia that offers two speakers and a sub woofer, as well as PC gaming, home stereo, car audio and mini component systems. The mini component systems are an example of the analog signal processing. A system like this drives sources like CD, DVD, CDR or Minidisk. These systems have their own DAC onboard so the output is analog and the output is fed into the analog signal processing. Analog Devices is moving those DACs, which are typically pretty poor performers, into a central processor - the SigmaDSP - and moving the processing to the digital domain. This will simplify the signal chain, improve the performance, and allow it to compete with existing analog solutions, a good move.

The normal configuration for the first SigmaDSP chip - the AD1954 - is for the left and right speaker DACs to be full range and the third DAC to be specifically low frequency, for the subwoofer. However, you don't have to work within the normal configuration of the part. ADI decided to provide flexibility by allowing you to program your own mode through the control port. All you do is download your custom programming using the graphical compiler. There is also a digital output that allows you to hook up an external stereo DAC for a five channel system, all use the SigmaDSP processing engine (3 onboard plus 2 external).

This is a very sophisticated chip and one of the most impressive parts is the dynamic processing of the compressor. It has dual band compression and treats the sub woofer channel separately from the main audio channel. At the output you see not only the three channels plus the digital output, another feature allows you to process low frequency information separately, even if you don't have a sub woofer in the system, and then sum all channels back into the left and right channels.

Another impressive feature of the chip is the GUI because it allows you to program the part and to know what's happening in real time. So if you move the bands on the equalizer, you hear the difference on the output. You can select from a range of filters that are the most common in audio, including peaking, butterworth, and others. ADI designed into the part a gang of IR filters to let you see what you are doing with the GUI. This way you are not preprogramming the core as you would with a general purpose DSP.

A significant advantage this chip offers for designers of say, car audio, is a reduction of parts on the shelf. For example, car manufacturers presently stock different amplifiers with different equalization for each car type. So the car manufacturers have a shelf of amplifiers for all the configurations of cars they have. SigmaDSP allows car manufacturers/stereo manufacturers to have one set of hardware and just a different program for each of those cars. So the car manufacturer needs a lot less inventory of amplifiers.

The AD1954 SigmaDSP digital audio processor is available in either a 44-pin MQFP or a 48-pin TQFP package and is rated for the extended -40ý C to +105ý C temperature range. The AD1954 is sampling now; production begins Q1 2002. Prices begin at $5.88 in 10,000-piece quantities. The 1954 will be released from production in January 2002.

More information