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The Absolute Sound
Issue 278   December 2017
Cutting Edge Digital Products
Editorial By Robert Harley

 

The Absolute Sound Issue 278 December 2017

 

  Reading the reviews in this issue of cutting-edge digital products prompted me to look back at some milestones on the path to the current digital era. It's easy to take for granted today's startling technology and tremendous advances in sound quality. Consider just one of our reviewed products, the Aurender A10 music server. It can hold thousands of albums on its internal storage and instantly access hundreds of thousands more via the Internet, all with a few taps on a tablet. Moreover, it includes an MQA decoder and DAC, delivering digital fidelity far beyond what anyone thought possible. This is Star Trek technology in the here and now. Consider what someone from the 1990s would think about the Aurender A10's capabilities.

I started reviewing full-time in 1989, just at the beginning of a creative explosion in digital audio. My first encounter with a serious assault on the state of the art was the Wadia 2000 Digital Decoding Computer in late 1989. The Wadia was more like a computer than an audio product, created by computer scientists rather than audio engineers. The 2000 was notable for its custom filter running on general-purpose DSP chips, four-box design, conversion of incoming datastreams to glass-fiber optical, and chassis machined from solid aluminum blocks. The price was $7700—a whopping amount at the time. The 2000 was an ungainly affair with its four black chassis and the cables that connected them, but it sounded totally unlike the relatively pedestrian CD players and inexpensive DACs that I'd been listening to. At that point, virtually all high-end DACs and CD players were built around a generic off-the-shelf digital filter chip; creating a custom filter was expensive and required a skill set not possessed by most high-end designers. My experience with the Wadia gave me the first early hint that a DAC's digital filter played a significant role in sound quality.

Although I never heard one in my own system, another landmark digital product of that era was the Spectral SDR-1000 CD player. This unit was way ahead of its time, incorporating selectable conjugate filters that corrected for phase errors introduced by different analog-to-digital converters, modular card-cage construction, and DC-megahertz discrete Class A topology (including a discrete current-to-voltage converter). The subsequent SDR-2000 was also superb, and although I have yet to hear it, the currently available SDR-4000 is, according to ears I trust, the state of the art in CD playback.

 

The Absolute Sound Issue 278 December 2017

 

The first DAC I heard that incorporated the UltraAnalog DAC module was the Stax DAC-X1t in 1991 ($12,000). The "t" in the model name denoted the tube output stage. The DAC-X1t was revelatory. Before the UltraAnalog DAC module, all DACs were built around DAC chips that had distortion caused by linearity errors. Simply put, linearity errors caused the DAC's analog output to be too high or too low in amplitude with certain digital input codes. Because of manufacturing tolerances, linearity errors varied among individual chips. To make matters worse, the lower the audio signal level (where detail, timbral color, and reverberation decay reside), the greater the linearity errors. And although these ubiquitous chips were touted as "20-bit" designs, they only had true usable resolution of 16 bits at best. UltraAnalog took a heroic approach by incorporating in a large potted module two DAC chips, one them converting the top 14 bits and the other the lower six bits for true 20-bit performance. Linearity error was virtually eliminated with an ingenious and labor-intensive method. Before the module was potted with epoxy, the DAC was fed by 100,000 specific digital codes and the resulting analog output levels for each code were measured. This information was fed to a computer, which told a technician exactly which "rungs" on the DAC's resistor ladder network had linearity errors, as well as the amplitude of those errors. The technician then hand-soldered tiny metal-film resistors in circuitry surrounding the DAC chips, eliminating the linearity error. I once watched this laborious process firsthand. In an era when DAC chips cost about $20, an UltraAnalog module had a wholesale cost of about $250.

The UltraAnalog DAC found its ultimate realization in the Mark Levinson No.30 Reference Digital Processor ($13,950 in 1992). The No.30 was a landmark in digital audio evolution, employing techniques and a level of execution never before seen. The main chassis (the power supply was separate) was flanked on both sides by towers that housed the DACs and analog output stages. Just enough cooling vents were provided to perfectly offset the internal circuit's heat production, keeping the UltraAnalog DACs at a constant and ideal temperature. The power supply was just as heroic, with multiple stages of discrete regulation. I was floored the first time I heard the No.30; it had a treble smoothness, ease, and resolution that vaulted it into a class of its own. A few weeks after receiving the No.30 (only three existed at the time) I picked up Ted Nakamichi (son of the eponymous company's founder) and his U.S. sales manager at the airport to take them to my home to listen to Nakamichi's new flagship DAC that I was scheduled to review. On the ride home, the sales manager, who was not shy about hyping his company's product, was touting the quality of the Nakamichi DAC, and at one point said, "It's better than the Levinson No.30." I replied (to his surprise) "Well, we can do that comparison. I have a No.30." We installed the Nakamichi DAC in my system and after listening to it, switched to the No.30. Ten seconds into the first piece of music the sales manager made an exaggerated physical gesture to convey how much better the Nakamichi DAC sounded (it wasn't the first or last time a sales guy has tried to spin listening impressions). But Ted Nakamichi, in the listening seat, sat silently and intently for the next 30 minutes as I played track after track. Finally, he turned to me and said quietly, "No.30 very good."

Although the No.30 was out of financial reach for most, the PS Audio UltraDAC wasn't. The $2000 UltraDAC wasn't the No.30's equal by any stretch, but for a fraction of the price it got you a lot of the way there. As its name suggests, the UltraDAC also used the UltraAnalog DAC modules. PS Audio sold a ton of them.

In the pantheon of landmark digital products, the Theta Digital DSPro series stands tall. Designed by Mike Moffat, the DSPro Generation III, IV, and V were all stunning. Built around custom digital filters, sophisticated analog stages, and heroic power supplies, the Theta DACs were the benchmarks in their price category, and challenged the very best in the world regardless of price. They were characterized by a "center-of-the-earth" solidity in the bass, a vivid and immediate presentation (in sharp contrast with the more laid-back Levinson), a sculpted and three-dimensional soundstage, and sledgehammer dynamic impact.

An across-the-board advance in digital sound quality was realized with the introduction in the mid-1990s of the Pacific Microsonics PMD-100 filter chip with HDCD decoding. Even when playing a non-HDCD source, the PMD-100 sounded much better than the NPC filter that was used in 90% of the DACs and CD players of the era. Before the PMD-100 your choice was an NPC filter chip or building your own filter from general-purpose DSP chips and writing your own filter software. It's worth noting that the PMD-100 filter was written by the brilliant Michael "Pflash" Pflaumer, the designer of today's Berkeley Audio Design DACs.

The most memorable product of the late 1990s was undoubtedly the Linn CD12 ($20,000). The fact that Linn bestowed on the CD12 the hallowed "12" designation (previously reserved for the LP12 turntable) says something about how the company viewed this design. It was right; the CD12 was shockingly good, and in ways that seemed to elude even the mightiest digital of the day. The compact brick-like machine (the chassis was a clamshell of two hollowed-out aluminum blocks that made it feel like a single solid structure) had a relaxed ease and communicative flow that I can still vividly remember to this day.

Fast-forward to the mid 2000s, and we come to the Meridian 808 V3 CD player, the product that introduced Meridian's "apodizing" filter that removed filter pre-ringing. This is a digital artifact in which some of a transient's energy occurs before the transient. Pre-ringing is particularly obnoxious because it's a type of distortion that never occurs in nature. The result was a smoother presentation, less grunge, and greater dimensionality. Today, most DACs use a filter that incorporates the apodizing technique.

The Berkeley Alpha DAC, still $4995, not only redefined what was possible from digital playback at the time of its introduction, it redefined the idea of value in digital-to-analog converters. I used one for many years at the front end of some reference-quality mega-priced systems, yet never felt like it was the weak link in the chain. Subsequent software upgrades extracted even more performance from this overachiever.

The Meridian 808 V6 CD player (2016) gets a nod for being the first consumer product with MQA decoding. I've written enough recently about the 808 V6 and MQA that I won't reiterate their virtues here, but suffice to say that the 808 V6 decoding MQA files was a turning point in digital audio's evolution.

I'm going to include in this pantheon a product that you may find surprising—the AudioQuest DragonFly Red. This $199 DAC represents the democratization of great digital sound. It's as good as, or better than, many of the highly vaunted mid-five-figure DACs of the 1990s. It's a milestone not in pure performance, or in introducing a new technology, but for making such great sound accessible to so many listeners. When fed from a good source and rendering an MQA file, the Red is astonishingly musical. The Red is everything that's wonderful about the high-end ethos bundled into a tiny, convenient, and affordable package that improves the listening experience for many music lovers who may not identify as audiophiles.

Finally, we come to the present day and what I consider the state of the art in digital playback, the Berkeley Audio Design Alpha Reference DAC ($19,950), now with a software update that makes it an MQA renderer. The Alpha DAC lacks a USB input, has no networking capability, and is an MQA renderer rather than a full MQA decoder (the first MQA "unfold" must be performed in external software such as the Tidal app or a music-server app such as the Aurender Conductor). But if you're willing to expend the effort to give the Alpha Reference the environment it needs, you'll be rewarded with a stunning wealth of detail, a huge soundstage with precisely defined images, a tangible sense of air between those images, bloom, dimensionality, rich and saturated timbral color, and a treble that integrates with the music rather than sounding like it rides on top. As great as the Alpha Reference sounded when I first heard it, this DAC sounds astonishingly better than the original, purely by means of software updates.

It's been a fascinating odyssey and a privilege to have heard the work of so many high-end designers who have never stopped innovating and finding ever more creative ways of configuring technology to make music listening more enjoyable.

 

 

 

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