Jonathan Scull returned to the Wotan in June 1998 (Vol.21 No.6):
A lot of electrons have flowed under the bridge since I brought you word of the mighty Vacuum Tube Logic Wotan MB-1250 (originally reviewed in Vol.19 No.10). While I was staggered by the awesome presentation of this $27,500/pair monoblock amplifier, I still found a few nits to pick. I was impressed by Luke Manley's "Manufacturer's Comment" response at the time. Instead of Excoriating the Reviewer, he took my nits seriously and said he'd address them. (Hey, he could be Mr. Magnanimous—it was a rave review!)
Fast…
The past 12 months have seen some remarkable developments in digital playback. Standards of digital musicality are far higher than they were a year ago, both on an absolute performance basis and in terms of what you get at various price levels. No other component category has seen such tremendous gains in value for money or number of new products introduced. It seems hard to believe that since Vol.13 No.6 (12 issues ago), we've reviewed such noteworthy digital processors as the Meridian 203, Proceed PDP 2, Stax DAC-X1t, Theta DSPro Basic, Wadia X-32, Esoteric D-2, PS Audio SuperLink, and VTL…
The DAC1's power supply—especially the discrete regulation stages—is quite impressive. I suspect that the unit could have been made significantly less expensive by using the more common IC regulators and electrolytic filter caps. But at what sonic cost?
Like many D/A converters, the DAC1's circuit topology includes the ubiquitous Yamaha YM3623B S/PDIF decoder chip (footnote 1) and NPC 8x-oversampling digital filter. Unlike most other digital processors, however, the DAC1 employs what is far and away the best-sounding (and -measuring) D/A converter extant: the UltraAnalog D18400 dual-…
The DAC1 also distinguished itself in its remarkable ability to clearly differentiate individual threads within the musical fabric. There was a complete lack of homogeneity and fusing of instrumental lines. Instead, each instrument was clearly delineated, both spatially and texturally, in the presentation, allowing its musical contribution to emerge. Percussion instruments, for example, had lives of their own rather than blending in with the rest of the music. The DAC1 revealed massed voices and strings to be made up of individual elements: each instrument's contribution was audible within…
By comparison, the VTL had a fatter, warmer bass rendering that was welcome on some music, but the DAC1 had better articulation and pitch definition. The Wadia 2000, however, was clearly the best in this department. It has an exceptional low-frequency drive and dynamic impact that was in sharp contrast to the DAC1's lightish, less visceral presentation. The sense of power, rhythmic drive, and energy was clearly greater with the Wadia 2000. Listening to the guitar and bass recording on the Stereophile Test CD, the DAC1 was missing the warmth and body of the bass. The VTL was perhaps overly…
Sidebar 1: Review System
The DAC1 was auditioned with the VTL 225W Deluxe monoblocks driving Hales System Two Signature speakers with the Muse Model 18 subwoofer via 3' runs of bi-wired AudioQuest Dragon/Clear bi-wire speaker cable. The preamp was either an Audio Research SP-11 Mk.II or the passive EVS Stepped Attenuator, while interconnects were AudioQuest Lapis (preamp to power amps) and AudioQuest Diamond (processor to preamp). I drove the DAC1 with the Esoteric P-2 transport via Aural Symphonics Digital Standard or TARA Labs Digital Reference.
In a fortunate coincidence, I…
Sidebar 2: Measurements
It's always reassuring to find excellent bench performance in a product that has first proven itself in the listening room. Conversely, products that sound good and measure poorly are cause for consternation: measured performance aspects that allegedly affect certain musical qualities are questioned. I had no such concerns, however, after measuring the DAC1: it exhibited excellent performance on the bench.
The DAC1's output level was the lowest I have measured, producing 1.74V when decoding a 1kHz, 0dB full-scale signal. This resulted in not quite enough…
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…
Sidebar 3: DAC1-20 Measurements
Like the original DAC1, the DAC1-20 performed very well on the bench. There was nothing in the measurements, however, that would indicate the sonic differences I've described. Rather than rehash the plots, the DAC1's measurements can be found starting on p.169 of the June 1991 issue. Any differences between the two units' performances are noted.
The two versions have identical output levels (a low 1.74V at full scale), frequency response, and de-emphasis error. Linearity, shown in fig.1, was superb, exhibiting 0.16dB error (left channel) and 0.03dB…
Sidebar 4: Specifications
Description: Frequency response: 0.01Hz–20kHz ±0.2dB. S/N ratio: 100dB (unweighted 20Hz–20kHz). Distortion: 0.002% at 1kHz (level not specified). Channel separation: 100dB at 1kHz. Phase linearity: ±0.5°, 20Hz–20kHz. Converter resolution: 18 bits. Input sampling frequencies: 32kHz, 44.1kHz, 48kHz. Three digital inputs: two coaxial on BNC jacks, one selectable between coaxial (BNC) and AT&T ST–type glass fiber-optic. Analog outputs: one unbalanced stereo pair on RCA jacks. Output impedance: 30 ohms. Power consumption: 25W.
Dimensions: 19" W by 5.25" H by…
