The high-end audio industry has a remarkable track record of making fundamentally limited technologies sound good. Most of these technologies were created for mass-market consumption where low price is the overriding design mandate. But because these technologies have become the standard, the high-end industry has had no choice but to attempt to create silk purses out of sows’ ears.
Here are just a few examples: the CD format (its creators would be astounded at the advances in just, say, digital filtering); the RCA plug and jack (compare the connections on 1970s equipment to today’s Cardas or WBT RCAs); and the Compact Cassette (Nakamichi 1000, anyone?).
A more recent, and perfect, example is the Universal Serial Bus, or USB interface. Designed to connect computer peripherals, USB was never intended to be a high-resolution digital-audio interface. But the rapid growth of computer-based music systems has, once again, foisted upon the high end a standard that requires exceptional re-engineering to meet the demands of high-quality music reproduction. Because of the contributions of high-end designers, today’s best USB interfaces are light years beyond the basic implementations.
In this overall drive toward a good-sounding USB interface, one company stands out for pushing the envelope—Berkeley Audio Design. The company that brought us the amazing Alpha DAC has turned its considerable engineering chops and uncompromising work ethic toward solving the USB interface problem. The Alpha USB reviewed here—only the second product from Berkeley—has been nearly two years in the making, largely, I surmise, because Berkeley is run by engineering-driven perfectionists who kept discovering during the design process better and better techniques and implementations. Berkeley is the kind of company that would repeatedly delay a product launch until it had wrung out every last bit of performance.
Why Do We Need a USB Converter?
Before looking at the Alpha USB in detail and considering its sound quality, let’s review the options for getting music out of a computer-based server and into a digital-to-analog converter (DAC). For now, we’ll ignore the turnkey systems such as Sooloos and the Olive O6HD (reviewed in this issue) to focus on do-it-yourself servers based on a personal computer.
The first option is to install a soundcard with integral DACs in your PC. You simply connect the soundcard’s analog outputs to your preamplifier and you’re in business. The compromises of this approach are fairly obvious—the inside of a computer is not the best place to perform digital-to-analog conversion. The second option is to use a soundcard’s S/PDIF or AES/EBU digital output for connection to an external DAC. In our previous issue (May/June) Karl Schuster surveyed and reported on eight such soundcards. This approach requires opening your PC to install the card, and configuring software. Moreover, building a PC server that is “bit transparent” (one that doesn’t change the ones and zero representing the music) is easier said than done.
The third method, which is by far the most popular, is to simply run a USB cable from the computer to a DAC equipped with a USB input. Although simple in practice, the USB interface audibly degrades the signal passing through it, even in the better implementations. As noted, USB was never designed for audio; it is a “packetized data” format in which data are split up into discrete chunks, wrapped up with information about those chunks, transmitted, and then put back together at the receiving end. This is in sharp contrast with the continuous bitstream of digital audio formats such as S/PDIF. Moreover, until recently USB has been limited to a maximum sampling frequency of 96kHz. And let’s not forget that many of us have older DACs that still sound good but lack a USB input. It is for these reasons that my own server, which I use exclusively to play high-resolution music, is a PC fitted with a Lynx AES16 card that outputs its digital signal as AES/EBU on an XLR plug. (I also use a Meridian Sooloos to access my CD music library.)
The solution to these myriad problems is an outboard box that takes USB from the computer and outputs S/PDIF—if this can be accomplished without compromising sound quality. Although USB converters are widely available, none could be considered an all-out assault on the state-of-the-art. Rather, they are largely utilitarian in purpose.
Which is where the Berkeley Alpha USB comes in. Berkeley’s goal with the Alpha USB was not just to create the best-sounding USB interface, but to completely eliminate the problems of USB and build a state-of-the-art solution for getting music out of a computer and into a DAC. Concomitantly, Berkeley wanted to create a product that allowed anyone, not just those with technical expertise, to realize state-of-the-art computer-based audio performance. When Berkeley’s Michael Ritter told me about the Alpha USB, he invited me to compare its sound with that of the AES/EBU output of the Lynx AES16 card in my fan-less, drive-less PC server, a setup that many considered the state-of-the-art in computer audio (see my review of this system in Issue 189). The PC with the Lynx card starts off with the considerable advantage of never converting the audio data to the USB format. If the Alpha USB did sound better than my PC (with both driving the same DAC), it would not only represent a breakthrough in sound quality, but make it much easier for non-geeky music lovers to enjoy the benefits of computer-sourced audio.