January 2010

Tools of the Computer Trade: Part One

In my review of NAD’s C 565BEE CD player last month, I said that it may well be the last CD player that I ever review, and that in 2010 I’d be concentrating on the future of high-end sound: computer-based playback of digital audio files stored on a computer and decoded by a high-quality digital-to-analog converter.

The audio world is going in this direction for some good reasons. One is that a computer can be more convenient than discs and a disc player. Today, with a decent high-speed Internet connection, a typical three-minute music track of uncompressed CD quality (16-bit/44.1kHz) constitutes about 30 megabytes, which can be downloaded in a few minutes. The contents of an entire CD (upward of 700MB) can be brought down in under an hour -- or even less, with a blazing-fast connection. Such rates of data transfer weren’t feasible a decade ago, and they weren’t even imaginable back in 1982, when the Compact Disc was introduced -- but they’re here today, and transfer speeds are likely to continue to increase. No more going to the record store -- the Internet is the perfect delivery vehicle for digitally encoded music, and your computer, provided you have enough storage space, is a great place to keep it: once those files are on your computer, songs and albums can be cataloged and indexed, making access to a virtually unlimited number of songs and albums only a few mouse clicks away.

Another benefit of computer storage and playback is the better sound quality of higher resolutions. The CD standard, set nearly 30 years ago, was a two-channel format with a word length of 16 bits and a sampling frequency of 44.1kHz. The CD’s 16-bit word length allows up to 96dB of dynamic range, and its sampling frequency was chosen because of the Nyquist Limit, which dictates that you must sample at twice the highest frequency that you wish to record; a sampling frequency of 44.1kHz allows the recording of frequencies up to 22.05kHz, which, at the time, seemed satisfactorily above what’s generally regarded as the upper limit of human hearing: 20kHz.

Not surprisingly, that decades-old standard has been surpassed. It’s now normal to make digital recordings with a 24-bit word length and a sampling frequency of 96 or 192kHz -- or 48, 88.2, or 176.4kHz. These longer word lengths allow a theoretical limit of 144dB of dynamic range, and the higher sampling frequencies of 96 and 192kHz permit the recording of sound frequencies up to 48 and 96kHz, respectively. These are significant improvements -- why shouldn’t our stereo systems at home support them? With a computer system, you can easily take advantage of these improvements; with CD playback, you can’t at all.

Of course, computer-based playback isn’t the only way to get this kind of resolution. DVD-Audio, SACD, and now Blu-ray Disc all offer hi-rez playback, and are still attractive to those happy with buying discs, and who don’t miss the convenience of downloading from the Internet. And all of these physical formats offer multichannel playback -- such files can still be time-consuming to download at high resolutions. But these disc-based formats have never generated much interest or "buzz" among audiophiles, let alone the masses: the DVD-Audio disc has been a complete failure in the marketplace, SACD has been relegated to the status of a niche product for audiophiles, and the music-only Blu-ray Disc has yet to catch on. A physical format might have been a necessary evil when the CD was born, but with the proliferation of the Internet and the continuing increases in download speeds, there’s no longer much need or desire for one. Show me one new music-only disc format that, since the advent of the Compact Disc, has caught on with the masses.

The future of high-resolution digital-audio playback involves, for audiophiles, the marriage of desktop and laptop computers to components made by high-end-audio companies, such as high-quality D/A converters, and the loudspeakers, cables, and other devices necessary to make it all work. It is these products, and how to combine and use them, that will be the focus of much of what I write about in 2010 and beyond. Next month, in "Tools of the Computer Trade: Part Two," I’ll tell you about my own computer-based audio system, which is taking me further away from CD and straight into the new, exciting world of high-resolution digital sound.

. . . Doug Schneider