Digital Processor Reviews

Robert Harley reviewed the DAC1-20 in December 1991 (Vol.14 No.12):

In the June issue of Stereophile (Vol.14 No.6), I raved about the $2995 Audio Research DAC1, the first digital product from the venerable Minnesota company known primarily for their tubed preamplifiers and power amplifiers. I found the DAC1 immensely musical, providing a presentation of digital sources that more closely emulated analog. Specifically, the DAC1 resolved layers and layers of finely woven detail, much the way good analog does. In addition, the DAC1 was smooth, transparent, and just plain musical. My primary criticism was that its bass was lightweight, lacking both extension and authority.

Having designed a superb product, ARC didn't rest on its laurels. Instead, they created a second version of the DAC1 using the 20-bit UltraAnalog DAC instead of the 18-bit UltraAnalog unit found in the original DAC1. The new model is thus known as the DAC1-20, and sells for $3495—$500 more than the DAC1. Owners of the DAC1 can have their units upgraded, either through their dealer or directly by the factory, for $595. In addition to including the better DAC, the 20 includes a Toslink optical input (a feature now standard on the 18-bit DAC1), and the line receiver has been changed from TTL to CMOS. The $595 upgrade price includes only the DAC and line receiver replacement; adding a Toslink input costs an additional $195. The Toslink input is sonically inferior to AT&T ST type optical or coaxial connection and is thus not recommended.

I was eager to hear the DAC1-20; I've been a big fan of the UltraAnalog A/D and D/A converters and was curious how much sonic difference there was between UltraAnalog's 18-bit and 20-bit converters. In addition, this "Follow-Up" provides an opportunity to comment further on the previously reviewed DAC1 after living with it for several months.

The DAC1-20 became my processor of choice during the past month. Associated components included the Theta Data transport, Audio Research's LS2 line-stage preamplifier, and Snell Type B, Hales System Two Signature with a Muse Model 18 subwoofer, and Apogee Centaur Minor loudspeakers. Power amplifiers were primarily the VTL 225W Deluxe monoblocks, with the Jeff Rowland Model 1 seeing some action. Interconnects were Straight Wire Maestro and AudioQuest Diamond, and loudspeaker cable was 8' runs of bi-wired AudioQuest Sterling/Midnight.

I must first reiterate my high praise of the DAC1. The more I listened to it the more I liked it. This is somewhat unusual in digital processors; extended listening usually reveals subtle quirks that begin to irritate over time. Not so with the DAC1. Its ease, liquidity, and sheer musicality made long-term listening enjoyable and unfatiguing (footnote 1).

But on to the DAC1-20. First, I was surprised by how different the 20-bit and 18-bit DACs sounded. My criticisms about the lightweight bass were somewhat ameliorated by the 20. There was a greater sense of weight and authority in the lower registers, giving music more drive and power. Plucked acoustic bass had a deeper, fuller, more resonant quality compared to the 18-bit, and bass drum carried more impact. Still, the DAC1-20 fell short of the rock-solid bass that characterizes the Theta and Wadia processors. Similarly, dynamics were improved with the 20, but weren't up to the standards set by these two families of software-based processors.

Surprisingly, the primary improvements rendered by the 20-bit DAC were those areas where the 18-bit version already excelled: transparency, liquidity, ability to reveal subtle detail, and an analog-like ease. The resolution of three-dimensional layering and depth was truly extraordinary. Image outlines were less vivid and sharply focused compared to the Theta processors (the Prime and Basic), but the DAC1-20 had a better ability to keep revealing layers of fine detail far into the soundstage rear, especially reverberation decay.

In comparison with the DAC1, the DAC1-20 had a greater ability to differentiate individual musical threads from the overall fabric. The DAC1 was excellent in this regard, but was clearly surpassed by the 20. For example, on the track "Restless" from violinist Mark O'Connor's The New Nashville Cats (Warner Bros. 26509-2), there is some high-spirited interplay between the violin and two guitars (footnote 2). Through the DAC1-20, I didn't have to work as hard to make out the individual instrumental lines; they were just there, distinct from everything else. This is an important element of music reproduction, and, I believe, one reason why digital has yet to surpass analog. When the ear/brain has to work to separate individual instruments from a synthetic continuum, there is less ability to absorb the music. This is one characteristic of the DAC1-20 that contributes to the analog-like ease noted.

For a more complete description of the DAC1's sonic character, see my review in the June 1991 issue. To get a better idea of what the 20-bit version sounds like, amplify the praise of its soundstaging, liquidity, and resolution of fine detail, and soften somewhat my criticism of the lightweight bass.

Finally, the DAC1 and DAC1-20 are products that are musically involving, yet don't call attention to themselves with "jump factor," etched detail, and bass slam. In fact, it's difficult to point to what makes them so musical and engaging. They just seem to convey the music's essence with a subtlety that defies description.

The DAC1-20 is an extraordinary D/A converter. It is, in my opinion, easily worth the $500 price increase over the original 18-bit DAC1. Although it lacks explosive dynamics and ultimate authority and warmth in the bass, these shortcomings are more than made up for by its other special qualities. The DAC1-20's ability to reveal layers of fine detail, portray natural tonal shadings, and throw a transparent soundstage make it competitive with the best converters in the world. In fact, I believe it to be unexcelled in these areas just mentioned.

Further, the DAC1-20 isn't "hi-fi" sounding, with lots of detail thrown at the listener. Instead, it is subtle, understated, and refined, resulting in a presentation closer to analog than any other converter I've heard.

The DAC1-20 is clearly toward the top of Class A in Stereophile's "Recommended Components," and may be the most musical converter I've auditioned. The fact that it costs much less than the competition makes it, in my view, the best buy in D/A converters today.—Robert Harley

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Footnote 1: I love to repeat Doug Sax's truism: "Every digital product that has been raved about has been reviled a year later."

Footnote 2: I'm not a country fan, but this album of mostly instrumentals, with former Dixie Dregs violinist O'Connor and some amazing Nashville studio musicians, is terrific.