Berkeley Audio Design Alpha DAC Reference Series

Reference, Indeed

Equipment report
Digital-to-analog converters
Berkeley Audio Alpha DAC Reference Series
Berkeley Audio Design Alpha DAC Reference Series

To understand Berkeley Audio Design’s ambitious new Alpha DAC Reference, you need to know something about the company behind it. In its six years of existence Berkeley had produced just two products: the $4995 Alpha DAC and the $1895 Alpha USB, a USB-to-SPDIF converter. The hugely successful Alpha DAC established a new level of performance for digital products at anywhere near its price. I lived for several years with an Alpha DAC in front of some stellar electronics and loudspeakers, yet never felt it was the weak link in the chain despite its modest price relative to the rest of the system. Similarly, the Alpha USB was light years ahead of any other USB-to-SPDIF converter I’d heard. Given Berkeley’s track record, I’d always wondered what this company could do if it aimed higher than the $5000 price point.

The answer has arrived in the new $16,000 Alpha DAC Reference Series, a vastly more ambitious effort than the venerable Alpha. Some potential purchasers will look at the Reference’s lack of a USB input or its omission of DSD decoding, and consider the unit a non-starter. That would be shortsighted. Both a USB input and integral DSD compatibility were omitted by design, which speaks volumes about the ethos of Berkeley founders Michael Ritter and Michael “Pflash” Pflaumer. Their approach could be summed up as “no sonic compromises.” If including a USB input in the same chassis as the DAC circuitry shaved off even a sliver of sound quality, it was ruled out. If performing DSD-to-PCM conversion brought performance down a notch, the decision was the same. Berkeley Audio, more than any other company I’ve encountered, is engineering and performance driven. A USB input and DSD decoding could easily have been included for marketing purposes, but that approach wouldn’t have accorded with Ritter and Pflaumer’s fundamental values.

The Alpha Reference is considerably more upscale in look and feel than the original Alpha. Although the Reference shares the Alpha’s front-panel display and controls, the Reference’s chassis is milled from a solid aluminum block, giving this 30-pound component a solid, brick-like feel. Front-panel switching includes input selection (two SPDIF, one AES/EBU, one TosLink), volume control, absolute-polarity inversion, filter choice, a button to change the display (volume, input sampling frequency, filter type, left/right gain), and a display dimmer. All these controls are duplicated on the handsome remote, along with a mute button and a balance control. LEDs indicate when the unit is locked to a source and if the input signal has been HDCD-encoded. The “Lock” LED glows amber when the Reference has established initial lock with the source, and then changes to green when the Reference locks to the source with a second, higher-precision clock. The Reference can drive a power amplifier directly with no need for a preamplifier in the signal path.

Both SPDIF inputs are on BNC jacks, not the typical RCAs. This is another example of Berkeley’s “no sonic compromise” approach. BNC connectors are not only the correct impedance (75 ohms); they also form a much more secure mechanical connection between jack and plug. Berkeley recommends AES/EBU; it has ten times the voltage compared with SPDIF (5V vs. 0.5V), which reportedly confers a slight advantage in timing precision. Balanced analog output is on XLR jacks, unbalanced on RCAs.

Although you can’t input DSD into the Alpha Reference, you can play DSD files by converting them to PCM in a Mac or Windows computer running the software playback engine JRiver Media Center. Buying an Alpha Reference gets you a license to JRiver. The rationale behind this approach is described in detail in the accompanying interview with Michael Ritter. If you want to drive the Reference with a USB output, you’ll need Berkeley’s Alpha USB.

Removing the heavy top panel and looking inside the chassis conjured up the image of a bank vault. The chassis’ solid aluminum block has been milled out to create three separate isolated chambers—one for the power supply, one for the front-panel display and control electronics, and one for the DAC, DSP, and analog output stages. This design confers several advantages, including isolation from outside noise and vibration, isolation between subsystems, and temperature stability.

I enjoyed using the Reference on a daily basis. The front-panel layout, labeling, and display, and the remote control are sensible and well thought out. The circuit design is similar in many ways to the original Alpha DAC, but implemented with new parts and build techniques impossible in a $5000 DAC. After listening to the Alpha Reference and considering its design, I realized that this must be one of the most cleverly engineered products I’ve reviewed. By that I mean that every dollar of the parts budget was laser-focused on optimizing performance, with nothing wasted on superfluities. The Alpha Reference also upended several of my biases about what it takes to create a state-of-the-art DAC. As you’ll see, the Alpha Reference sounds spectacular, and yet it realizes this unprecedented sound quality with what looks like a fairly conventional power supply (no outboard box filled with dozens of stages of cascaded discrete regulation), an off-the-shelf DAC chip (from Analog Devices), and an op-amp output stage. What you don’t see are the extraordinary parts and the design techniques that have been applied to the subsystems that really matter, particularly the clocking and the hand-calibration of the analog filter. Berkeley has figured out exactly where to spend its parts budget—and where not to.