Berkeley Audio Design Alpha DAC

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

Most audio products designed for professional use are sonically inferior compared to the best high-end “consumer” components. That’s because, in the pro world, features, functionality, and reliability under harsh conditions take precedence over sound quality. And odd as it might sound, most professionals are more price-sensitive than audiophiles.

A notable exception is the new Alpha DAC digital-to-analog converter from Berkeley Audio Design. Although outfitted with professional features, the Alpha DAC is designed to bring first-rate digital-to-analog conversion to both pros and audiophiles. That’s not such a stretch considering that the Alpha DAC’s design team also created High Definition Compatible Digital (HDCD), as well as the Pacific Microsonics Model Two, widely considered among both pros and knowledgeable consumers as the finest analog-to-digital and digital-to-analog converters extant. The Model Two is the professional high-resolution A/D converter and HDCD encoder found in the world’s best mastering rooms. Most of the Pacific Microsonics design team reformed as Berkeley Audio Design, turning its attention to making a D/A converter capable of decoding high-resolution sources.

The Alpha DAC’s professional orientation is apparent from the unit’s form factor, features, and front-panel layout. The small chassis is sturdy and nicely finished, but utilitarian by high-end standards. Similarly, the front panel is all business and no fluff; the panel is loaded with essential controls and indicators. A large alphanumeric display shows the input sampling rate, from 32kHz to 192kHz. Small LEDs indicate the selected input, signal lock, HDCD decoding, polarity inversion, and the selected digital filter. A pair of buttons next to the display adjusts the output level; the Alpha DAC is designed to drive a power amplifier directly. The display automatically switches to show the output level when the output level is being adjusted. Although you can, of course, treat the Alpha DAC like any other source component and run its output through your preamplifier, the Alpha DAC only reveals its full potential with no preamplifier in the signal path—particularly when decoding high-resolution sources. A remote control allows you to adjust level, channel balance, polarity, muting, input selection, and display dimming.

Another of the Alpha DAC features that reveals its professional roots is the selectable digital filter. This feature isn’t provided so that you can “tune” the DAC to your system or personal preference. Rather, there’s one filter that is absolutely optimum (Filter 1), while the other filters allow mastering engineers to hear how their work will sound on the digital filters typically found in consumer CD players. One of the filters is identical to the Pacific Microsonics PMD-200 found in many high-end CD players. Incidentally, the availability of the PMD-100 and PMD-200 in the mid-1990s greatly improved the sound of CD players at the time. The Pacific Microsonics 8-X oversampling filter (with HDCD decoding) replaced the ubiquitous NPC filter chip, rendering a wholesale improvement in CD sound.

A rear-panel RJ-45 jack marked “BADA” (Berkeley Audio Design Alpha) is designed to accept encrypted high-resolution from an outboard decoder of DRM-protected music. The idea is that the outboard box would strip music of DRM and then encrypt the data for transmission over the BADA interface. This arrangement meets the licensing laws while providing listeners with uncompromised playback of DRM-protected files. Although such forward-thinking is welcome, record labels are quickly abandoning DRM. Another forward-thinking touch is the Alpha DAC’s ability to receive upgraded firmware simply by playing a CD with the upgrade encoded on it and feeding the CD transport’s output into one of the Alpha DAC’s digital inputs.

The Alpha DAC’s design and build-quality are somewhat paradoxical. On one hand, the unit employs unusual and extremely sophisticated circuits. On the other, it doesn’t look like a conventional high-end product, lacking the massive power transformers, banks of power-supply regulators, large discrete output stages, and other staples of high-end DACs. The unit features Analog Devices DACs followed by op-amp output stages (the op-amps’ markings have been removed). Berkeley says the op-amps were chosen not to save cost or board space, but because they best realized the technical and sonic goals of the Alpha DAC. The unit employs some proprietary technologies and is meticulously hand-tuned: Each unit is aligned, burned-in under load for seven days, aligned again by hand, and listened to before being boxed for shipment.

The Alpha DAC is based largely on the body of knowledge developed by the Pacific Microsonics design team in creating High Definition Compatible Digital (HDCD) and the professional Model Two HDCD encoder/decoder. The Alpha DAC’s primary designer is Michael “Pflash” Pflaumer, a Pacific Microsonics co-founder who, among other achievements, wrote the DSP code that realized HDCD encoding and decoding (including the PMD-100 and PDM-200 digital filters). For the Alpha DAC, he wrote a new and advanced digital filter that runs on an Analog Devices SHARC processor. Although the Alpha DAC’s components and circuit topology are considerably different from that of the Model Two, this new product reflects the fundamental insights gained during the multi-million-dollar design effort on the Model Two.


Evaluating the Alpha DAC was more complicated than auditioning a conventional D/A converter. Rather than simply connect a CD transport to one of the Alpha DAC’s digital inputs, I had the ability to play high-resolution and standard-resolution files courtesy of a PC-based music server described in the accompanying article on Reference Recordings’ HRx format. My description in that article of the sound of the 176.4kHz/24-bit HRx files is in large part a description of the sound of the Alpha DAC.

Starting with the Alpha DAC decoding standard-resolution (44.1kHz/16-bit) sources from the music server, the Alpha DAC delivered some of the best-sounding CD playback I’ve heard. First, the Alpha DAC has that rare (and musically important) quality of resolving lots of information without sounding analytical, hyped, or “hi-fi-like.” The Alpha DAC presents to the listener a tremendous amount of low-level detail such as delicate spatial cues, the finely filigreed harmonic structure that defines instrumental timbres, and the gossamer-like quality of the very end of reverberation tails. Most digital products truncate this information, or present it as coarse and grainy rather than with a silk-like delicacy. A visual analogy is a pixilated image on a digital TV transmission with poor reception. The lower the signal level, the greater this effect.

The Alpha DAC is highly resolving at all signal levels, but it’s this ability to dig down into the lowermost levels that elevates its performance into the top level of digital playback. Just as important, the Alpha DAC doesn’t call attention to its resolution; rather, it is suave, understated, and refined. It’s the kind of resolution that conjures a vivid impression of the mechanism by which an instrument created a sound, the palpability of tone color, and the precise spatial relationships between instruments within a recorded acoustic. All this information is delivered in a completely natural and unforced way, fostering a tremendous sense of ease, relaxation, and musical involvement.

The Alpha DAC is also capable of huge dynamic contrasts, along with a lightning-fast portrayal of transient information. The music swings effortlessly from quiet to full-scale with tremendous speed, but with no sense of etch on the transient leading edges. The rest of my system is particularly adept dynamically (Spectral DMA-360 amplifiers, MIT Oracle MA interconnects and cable, and Wilson X-2 Series 2 loudspeakers) which allowed me to hear the full measure of the Alpha DAC’s extraordinary lifelike reproduction of transients, lack of smearing, and ability to present music’s dynamics intact.

Perhaps because of this tremendous agility I was more aware of the musicians’ rhythmic and dynamic inflections. There was a distinctly greater sense of the music sounding upbeat and lively, of the band “locking into” the groove, and of a heightened physical involvement in the music. The music had a greater coherence, energy, and life that was akin to the difference between a tight band playing on a good night vs. on a great night. This is a DAC that involves your whole body in the music in a visceral and emotional way, not just in an intellectual abstraction of the sound’s component parts.

The Alpha DAC’s sense of transparency was startling. The presentation had a pristine clarity and vividness that seemed to strip away a fine scrim between the soundstage and me. Although the sound had a sense of precision, definition, and alacrity, it was never cold, sterile, or analytical. I’ve heard digital products that cover up the digital nasties with a syrupy romantic sound, as well as others that one might admire intellectually for their precision but not enjoy musically. Never before have I heard an outboard DAC that combines musical vividness with such ease, grace, and involvement as the Alpha DAC. Similarly, timbres were simultaneously immediate and palpable, yet gentle and relaxed. There’s long been a conflict in the high-end about “musicality vs. accuracy.” I believe this is a false dichotomy; accuracy is musicality when the sound is truly accurate and not merely a hi-fi-like representation of reality.

Finally, the Alpha DAC is simply sensational in its soundstaging. Instruments and voices are localized with scalpel-like precision within a huge and transparent acoustic. In addition to getting right the macro-aspects of depth and width, the Alpha DAC was supremely adept at resolving very fine spatial details that define an instrument’s relation to the surrounding acoustic. I heard a wonderful sense of bloom and what Jonathan Valin calls “action”—the impression of air expanding dynamically from an instrument.

The Alpha DAC was so good it invited comparison with the best CD playback I’ve heard, the Spectral SDR-4000 Pro CD player. This comparison wasn’t definitive; playing the same music in the Spectral via its transport mechanism, or through the Alpha DAC sourced from the music server, introduced variables. The Spectral had the advantage of no digital interface in the signal path and thus lower potential jitter. The Alpha DAC, on the other hand, was fed the output of a solid-state memory which, in my experience, produces a better sound than reading data from an optical disc on the fly. In addition, the Alpha DAC and the Spectral both fed a preamplifier via unbalanced outputs, obviating the Alpha DAC’s advantageous ability to bypass a preamplifier and drive a power amplifier directly. It was also impossible to compare the two devices on a level playing field when sourced from the same transport mechanism; the Spectral’s digital output is coaxial on an RCA jack; the Alpha DAC’s coaxial digital input is on a BNC connector. Although a BNC transmission line is technically superior to one terminated with RCA connectors, introducing an RCA-to-BNC converter would not have provided a fair comparison.

Nonetheless, the juxtaposition was interesting; the two products sounded remarkably similar. The Alpha DAC was a bit more forward and lively through the midband and lower treble, with timbres sounding more “illuminated from within.” The SDR-4000 Pro had a slightly more distant spatial perspective and greater midrange liquidity. This character of the Alpha DAC was, however, somewhat dependent on the AES/EBU cable feeding it. The Alpha DAC and Spectral had similar degrees of resolution, although the Spectral had a bit more air and space around instrumental images. The SDR-4000 was also a little warmer in the midbass, with a greater sense of texture.

I describe the Alpha DAC’s sound relative to the Spectral not because they compete with each other; they are very different products that serve different needs. Rather, I compare them to illustrate just how close the Alpha DAC comes to the state-of-the-art (at least in my experience) in CD playback, and indeed, to note how similar they sound. Interestingly, they both employ a custom digital filter that incorporates HDCD decoding running on an Analog Devices SHARC DSP.

But listening to the Alpha DAC with only 44.1kHz/16-bit sources is like driving a Ferrari without leaving first gear; it’s thrilling, but only hints at the possibilities. When decoding 176.4kHz/24-bit files from the music server, the Alpha DAC is jaw-dropping. The resolution of fine detail I heard from CD was taken to an entirely new level. In fact, I concluded that the Alpha DAC sounds so detailed with 44.1kHz/16-bit sources because it was designed fundamentally to resolve the extraordinarily low-level detail of high-res sources. When fed Reference Recordings’ 176.4kHz/24-bit files from the music server, the Alpha DAC driving the Spectral DMA-360 amplifiers through MIT Oracle MA and Wilson Alexandria X-2 Series 2 loudspeakers produced the most thrilling audio experience of my life. See my accompanying article on Reference Recordings’ HRx format for more on the Alpha DAC’s sound with high-resolution sources.


The Berkeley Audio Design Alpha DAC is the best-sounding outboard digital-to-analog converter I’ve heard. The fact that it decodes high-resolution sources of any sampling rate and word length is icing on the cake. Although the Alpha DAC is spectacularly great on CD, this converter really shows its prodigious resolution, dynamic agility, and soundstaging capabilities when fed 176.4kHz/24-bit digital audio. Moreover, the Alpha DAC’s feature set, operation (instant locking to changing sampling rates, for example), and ability to drive a power amplifier directly expands the product’s utility and makes it ideal for the next generation of high-resolution music servers that is just around the corner.

The real story, however, is that this performance and functionality is possible at $4995. Although not inexpensive, the Alpha DAC nonetheless competes with, and outperforms, much more expensive converters. At $5k, the Alpha DAC is a spectacular bargain. It is my outboard converter of choice for both CD and high-resolution sources—regardless of price.