Digital Processor Reviews

If there's one buzzword in high-end audio for the 1990s, it's undoubtedly jitter. "Jitter" describes timing variations in the clock controlling the ones and zeros that represent the analog audio signal. If that clock isn't stable to an extraordinarily precise degree, the sound quality of the digital processor will be degraded.

A CD transport/digital processor combination introduces jitter in three ways: 1) the transport puts out a jittered signal; 2) the S/PDIF or AES/EBU interface between the transport and processor creates jitter; and 3) the digital processor adds its own jitter to the clock. These additive factors are largely responsible for the great range in sound quality we hear from different transports and interfaces.

Remember the early days of CD, when some players were touted as having the revolutionary new "2x-oversampling" digital filters?

Ten years ago, the average consumer was unaware that he or she needed an e-book reader. Since that time, neither those people nor the authors whose books they consume have changed very much. But the people in between have grown restless and unsatisfied, and it is they who call the tune. Consequently, many of you have gone from owning books to sort of, kind of owning books (and sort of, kind of not).

Even the most savvy Stereophile reader might wonder what a "network music player" is. Linn rightly considers a music server to be a combination of 1) stored digital files, 2) music-management software, and 3) a device that uses #2 to transfer #1 to your hi-fi. What Linn's Klimax DS is is a high-quality digital-to-analog converter (DAC) that receives digital data through an Ethernet connection rather than optical or electrical S/PDIF or AES/EBU inputs.

I'm beginning to understand why some people enjoy writing about crazy tweaks like electron counseling and magic listening trousers: When an idea is that new, it brings with it the chance for some gifted but heretofore unappreciated journalist to rise through the ranks and describe it to an anxious world. By contrast, when a defeated and baggy old establishment writer sets out to describe a CD player or amplifier, the product is surely the millionth such thing to come down the pike, and before long the readers complain: We used to like you, but you don't try very hard to excite us anymore.

In the summer of 1999, Sony held a press event in New York City to mark the introduction of the Super Audio Compact Disc, then the sole domestic embodiment of the Direct Stream Digital (DSD) technology, jointly developed by Sony and Philips. The new format was hailed, in prepared remarks, by an impressive list of audio and music dignitaries: Nobuyuki Idei, then president of Sony Corporation; Steven Epstein, senior executive producer for Sony Classical; Yo-Yo Ma, appearing in a video created for the event; and Wynton Marsalis, appearing in person. All of the speeches—every single one of them—flattered SACD by likening its sound to that of the analog LP.

You know what's fascinating? As digital audio technology matures, DAC design is not converging on a single most popular or overall best approach. Multiple design paths continue to thrive, new ones are still appearing, and each variation on the DAC theme has its adherents and side trails: bitstream, non-oversampling, upsampling, various filters, DSD playback options, and on and on.