Editor's Introduction: In 2013, lossy compression is everywherewithout lossy codecs like MP3, Dolby Digital, DTS, A2DP, AAC, apt-X, and Ogg Vorbis, there would be no Web audio services like Spotify or Pandora, no multichannel soundtracks on DVD, no Bluetooth audio, no DAB and HDradio, no Sirius/XM, and no iTunes, to quote the commercial successes and no Napster, MiniDisc, or DCC, to quote the failures. Despite their potential for damage to the music, the convenience and sometimes drastic reduction in audio file size have made lossy codecs ubiquitous in the 21st century. Stereophile covered the development of lossy compression; following is an article from more than two decades ago warning of the sonic dangers.Editor
Over the past two and a half years, I've auditioned and reviewed a number of digital audio products. It has been a fascinating experience both to watch digital playback technology evolve and to listen to the results of various design philosophies. The road to more musical digital audio has been a slow and steady climb, with occasional jumps forward made possible by new techniques and technologies. Making this odyssey even more interesting (and confounding), digital processors seem to offer varying interpretations of the music rather than striving toward a common ideal of presenting what's on the disc without editorial interjection.
The arrival of the Mark Levinson No.30 digital processor more than 2½ years ago marked a turning point in digital-audio reproduction. Although the No.30's $13,950 price tag put it out of reach of all but a few audiophiles, its stunning performance suggested that much more musical information was encoded on our CDs, waiting to be recovered by better digital processors. Further, it was inevitable that this level of performance would become less expensive over time. I was more excited by the No.30 than I've been over any other audio product. In fact, its musical performance was so spectacular that it alone occupied the Class A category in Stereophile's "Recommended Components."
At a "Meet the Designers" panel discussion at the 1992 Los Angeles Stereophile High-End Hi-Fi Show, I asked a group of successful digital designers (footnote 1) each to state how much of a digital front end's sound quality they believed was due to the transport, digital processor, and interface between the two. There was virtual unanimity: Nearly everyone agreed that a digital processor accounts for about 50% of a digital source's sound quality, the transport 30%, and interface 20%.
High-end audio companies take different approaches to staying successful. One way to maintain a market position is to continue improving fundamental designs, offering a little higher sonic performance with each model. The latest products from a company employing this approach will look and operate very much like their first products.
For many audiophiles, choosing a power amplifier is a vexing problem. Just how much must one spend to get true high-end sound and a solid build quality? How much power is really needed? And what amplifiers are suitable for driving low-impedance loudspeakers?
There are as many ways of designing a digital-to-analog converter as there are engineers. One approach is to select parts from manufacturers' data books and build the product according to the "application notes" provided by the parts manufacturers. This is the electronic equivalent of a paint-by-numbers kit.
A more creative engineer may add a few tricks of his own to the standard brew. Bigger and better regulated power supplies, careful circuit-board layout, tweaky passive components, and attention to detail will likely make this designer's product sound better than the same basic building blocks implemented without this care. Indeed, the vast range of sonic flavors from digital processors containing very nearly the same parts attests to the designer's influence over a digital processor's sound.
Whoever invented the adage "Good things come in small packages" wasn't into high-end audio. Most high-end products are huge and heavy, with massive power supplies, thick front panels, and battleship build quality. This dreadnought approach is justified if it directly affects the unit's sonic performance (as in the Mark Levinson No.31 transport, for example). In some products, however, the massive build can reflect a shotgun, overkill approach by the designer, or a mere fashion statement.
His background may have been in tubed audio product design, but Theta Digital's Mike Moffat is now at the forefront of computer-based digital processor development. His Theta D/A processors are among a handful of products that use Digital Signal Processing (DSP) chips and custom filtering software instead of off-the-shelf filter chips (footnote 1). I recently visited Mike at the Theta factory to get his current ideas on digital audio reproduction and what goes into designing a good-sounding processor. I began by asking Mike if he had always been an audiophile.