The high end’s trademark is sonically meaningful evolution; revolutions are rare. USB, however, gives every indication of being the latter. Though its roots are pedestrian—the interface was designed to facilitate connectivity between computers and standard peripherals—USB now augurs a potential sea-change in the way audiophiles acquire, store, and play music.
In the USB world, PCs serve as the primary audio source. They store entire music libraries, yet offer the ability to access desired material—based on any number of criteria—without the need to scour a single dusty shelf. Silver discs are history, all of them having been “ripped” to the PC. New music need not ever reside on such physical media, for it can be downloaded with a click. Playback emanates from hard drives, which sound better than optical disc readers. And, perhaps most importantly from a sonic standpoint, CD-quality sample- and bit-rates are no longer a barrier; PCs and USB both support much higher resolution levels.
Dedicated music servers can do all this, too. But they tend to be expensive and are still in limited distribution. In contrast, USB empowers anyone who owns a PC to reap the benefits of purpose-built music servers.
Of course, a stock PC does not a music server make. To assume that mantle, PCs require a support ecosystem that includes hard drives with the capacity to store a music library, Web sites offering a varied selection of music in formats from MP3 to HD, and user-friendly music-server software. As it happens, all of these essentials are already in plentiful supply, many of them for free or close to it. The final necessary element in this ecosystem is a means for the PC to connect to the rest of the playback chain. This is where USB comes in.
True to its first initial—the other two stand for Serial Bus—USB is indeed “universal” among PCs, making it the natural choice for such a connection. But there must also be something within the audio system that supports the same interface. For high-end installations, that something is a USB DAC—and manufacturers are unleashing a flood of them. Indeed, USB has become a checklist feature; new DACs exclude it at their competitive peril. Meanwhile, for those with “legacy” DACs, a new component class has emerged: the USB-to-S/PDIF converter. With these offerings, the audiophile industry has delivered the last pieces needed to realize a sonic revolution.
But let’s step back a minute. Before clasping USB to our collective bosom, shouldn’t the high end first ask some basic questions about this interface, such as how does it actually sound? TASthinks so. Which is why yours truly spent roughly six months listening to and generally playing around with USB as delivered through a score of PCs, software programs, cables, DACs, and converter boxes. I was seeking credible, reliable answers to fundamental USB-related questions. And because my experiences with the interface proved remarkably consistent across time, products, and source material, I believe I found them.
Before delving into those questions and answers, though, a few notes about the test bed. The primary source device through this journey of exploration was my own current-generation HP Pavilion laptop PC running the latest version of Windows Vista. (As anyone who follows the various computer-audio Web sites knows by now, Vista outstrips XP as an audio platform because of the latter’s sonically destructive, difficult-to-bypass kernel-mixer module.) Other sources in my test bed included an Apple iMac G4 running OSX, as well as a custom-built desktop PC sporting Windows 2000 and an upgraded internal sound card. These disparate machines and operating systems enabled me to assess not only the nature of USB audio, but any platform-based variations.
Naturally, all three computers had USB ports, but the HP and Apple also offered a FireWire interface, while the custom machine’s enhanced sound card could deliver high-resolution coax S/PDIF. All this flexibility allowed me to methodically compare USB to alternative interfaces.