For audio software, I loaded my laptop with MediaMonkey, a free program recommended by high-res music sites such as HDTracks. To allow a software comparison, I also installed the less-user-friendly but more sophisticated Foobar 2000. Unfortunately, both of these are Windows-only programs so I was forced to run iTunes on the Mac. I say “forced” because I consider iTunes fatally flawed in that it outputs data at a fixed resolution rather than adopting, on the fly, the sampling rate of the source material. Failing—or simply forgetting—to manually set the proper sample rate for a given track triggers a sonically detrimental rate conversion.
When it came to selecting USB DACs for these sessions, my biggest challenge was narrowing the burgeoning field of candidates. In the end, I chose the Benchmark DAC1 Pre, Bryston’s brand new BDA-1, the equally fresh Audio Research DAC7, and my trusty, Golden Ear Award-winning Resolution Audio Opus 21 stack. (Wavelength Audio, which builds intriguingly innovative USB DACs, unfortunately declined to participate in these tests.) I also spent considerable time evaluating the Bel Canto USB Link 24/96 (a USB-to-S/PDIF converter) and the Focusrite Saffire (a FireWire-to-S/PDIF converter). All of these DACs and converters drove my standard reference system.
Q: First of all, do you really need a USB DAC?
A: In most cases, not really. To understand why, consider the various sources that might drive a DAC. The first category is CD and universal transports. None have USB outputs; all use S/PDIF. The next group is dedicated music servers. Ironically, given that these devices are essentially tailored computers, USB is a rare inclusion while S/PDIF is ubiquitous. How about desktop PCs? They have no need for a USB DAC either. The reason is that these computers are stationary and typically not co-located with the audio system. In order to make contact with the latter, desktop machines rely upon either wired or wireless audio distribution. In such an arrangement, the remote device—not the computer—resides by and connects to the audio system. Once again, among these devices (e.g., Apple’s Airport Express) S/PDIF is the standard output.
That leaves laptops. Here, as previously noted, USB is pervasive. Yet laptops often have another output suitable for music playback. The IEEE 1394 FireWire interface is widespread on products from HP, Dell, Apple, Toshiba, and Sony, and the pro recording industry offers a bevy of boxes that convert FireWire to—you guessed it—S/PDIF. For PCs that lack FireWire, there are now USB-to-S/PDIF converters that likewise obviate the need for a USB interface on the DAC. All of which nets out to this: A USB DAC is necessary only if one’s source is a laptop—and even then, onlyif straight-through USB (i.e., with no converter in the signal path) is the best-sounding option available.
Q: How difficult is it to connect a laptop to a USB DAC?
A: It’s easy. USB DACs are designed for plug-and-play ease of use. Just string a USB cable between the DAC and the PC, then select USB from among the DAC’s input options. When you first make the link, the PC will recognize the DAC as an audio device without so much as the need to load drivers. You will, however, have to tell the operating system that you want your audio funneled to the DAC. This is easily done. On a Mac, go to System Preferences->Sounds->Output. That will bring up all available output devices, at which point you simply select the USB DAC. The procedure is much the same for Windows machines, where the sequence is Control Panel->Sound. In Windows, after selecting the DAC, you will need to click on either “Apply” or “Set Default,” whichever your system presents. Then, and only then, launch your music software (iTunes, MediaMonkey, etc.). You are ready to play music.