Digital Processor Reviews

Art Dudley wrote about the Azur 851D in February 2015 (Vol.38 No.2):

It's November 18, and by the time you read this my family and I may be snowed in. Soon enough, our driveway will become an obstacle for the man who delivers our firewood, the man who delivers our drinking water, and our local UPS and FedEx couriers.

One delivery came in under the wire. Last week our UPS man, whom we would recommend for canonization were such a thing within our powers, came by with an unexpected parcel: John Atkinson had forwarded to me the magazine's review loaner of Cambridge Audio's Azur 851D D/A processor ($1649), which Jon Iverson had reviewed for Stereophile's December 2014 issue.

The UK-designed, Chinese-built Azur 851D is an upsampling processor that bumps up the digital signal to 24-bit/384kHz before converting it to analog. It offers no fewer than 10 digital inputs, including USB versions 1.0 and 2.0, and accepts datastreams of up to 24/192 on all inputs except TosLink and USB 1.0, which are limited to 96kHz (footnote 1). As a bonus, the 851D is packaged with a Cambridge Audio BT100 Bluetooth dongle (an embarrassingly precious word that rivals Ogg Vorbis in its betrayal of computer audio's dweeb roots, but there you have it), a USB-A socket for which is provided on the 851D's rear panel.

Before I learned anything about the Azur 851D—before I visited Cambridge Audio's website, before I read JI's review, before I had even a rough idea of its price ($1649)—I unpacked it and hooked it up to my system. With my Apple iMac computer and Audirvana Plus 1.5.12 playback software, the 851D proved to be one of those products that resisted all efforts to switch back and forth between it and other USB processors with anything like speed: only after I'd fully exited and then restarted Audirvana Plus would the 851D accept incoming datastreams. Apart from that little speed bump, setup was unremarkable and easy.

I proceeded to spend a couple of hours listening to the 851D, primarily with AIFF files of some favorite classical and jazz recordings. (The Cambridge doesn't do DSD.) I was very impressed, and made note of the 851D's excellent color, texture, and musical momentum and flow: It truly played music, and sounded great while doing so.

Then I read up on the 851D—including the measurements, by JA, that accompanied JI's review. JA observed that, even into a load of 600 ohms, the 851D's only harmonic product of significance was 0.003% second-harmonic distortion. I couldn't help being surprised, since so many of my favorite products offer much more of the stuff. In a double-blind test against my Halide DAC HD, I'm sure I would have chosen the superior-sounding Cambridge 851D as the more distorted (footnote 2).

Seriously: I often prefer products that are well engineered in a traditional sense; ie, those that perform better on the test bench than their competitors. As for those instances when the combination of my tastes and my listening priorities have pulled me in a contrary direction, I have no explanation that would satisfy anyone who would require such a thing. (For more on the topic, see this month's "Listening" column.)

The fact is, the Cambridge Azur 851D calls into question not my preferences or priorities, but my previously held, if vaguely supported, notion that a really top-flight digital source must cost at least $4000. I will probably lose any right to make fun of dongle by trafficking in such clichés, but the Cambridge 851D is, indeed, a killer of giants. It is a D/A converter that uses its high resolution not to add amusical filigree or spatial puffery, but to enhance musical flow and drama. It really is that good.

An apt example: Using Jascha Heifetz's second recording of Bruch's Scottish Fantasy, with Sir Malcolm Sargent and the New Symphony Orchestra of London, released on vinyl in 1961 (RCA Living Stereo LSC-2603) and on CD in 1987 (BMG 61745-2), I began by comparing an AIFF made from the CD and played through the Halide DAC HD to an original copy of the LP I picked up nearly 30 years ago at a now-defunct bookstore in Yonkers. The Halide got the gist of it—which is more than can be said for a great number of digital source components, cheap or expensive. During some moments in the music when the LP was all openness and shimmer, the Halide filled in with a not-unattractive burnish. And the Halide's sense of detail was good: The violin's exquisitely soft opening note was almost as distinct through the DAC HD as from the LP. But some texture was lacking in the sounds of just about everything. Orchestra fortes sounded somewhat pinched. And, most notable, the Halide didn't have nearly the same generous sense of scale as the LP. Verdict: For $500, no record wear, and no need to replace needles, the Halide was awfully damn good. It wasn't as satisfying as the vinyl, but it merited comparison.

The Cambridge 851D was nothing short of shocking: It trounced the Halide and came close enough to the LP to scare if not actually bite it. The Cambridge allowed Heifetz's violin the same clear delicacy in its opening notes as the vinyl, and allowed the orchestra as great a sense of scale as heard from the LP. The sound through the Cambridge was open, yet with no lack of substance. Heifetz's tone, especially at the opening of the Finale: Allegro guerriero, was nothing short of exquisite. And the Cambridge made me realize that Sargent had, in this piece, a much more flexible sense of time than I'd ever before appreciated: More than once, a very subtle accelerando made itself apparent, especially in the plucked double basses during the introduction. Only in its conveyance of physicality—in the plucked strings of the harp, the breath behind the horn, the strike of the cymbal—and in its conveyance of the last iota of timbral saturation, did the LP win out.

The pleasures of the Cambridge were not limited to classical warhorses. In "Far from Me," from Nick Cave's indispensable The Boatman's Call (rip from CD, Mute/Reprise 46530), the pitches of notes played on the electric bass were, through the Halide, somewhat indistinct—even though the sound of the bass was rich and colorful. Through the Cambridge 851D there was no less color, no less weight than through the Halide, yet the notes were unambiguously, man-on-the-street clearer. Vocal articulation was also much better through the Cambridge, without the slightest added brightness. Much the same could be said about "The Way the Whole Thing Ends," from Gillian Welch's The Harrow & the Harvest (rip from CD, Acony ACNY-1109)—an extra delight being the superior way in which the Cambridge articulated the beginning of David Rawlings's guitar solo, and its very physical repeated slide from an open D to G (footnote 3).

Secondary to its musical prowess but still of considerable importance was the Azur 851D's flexibility—especially its Bluetooth connectivity. As amateur musicians who regularly play with other amateur musicians, I and my colleagues commonly load up our iPhones with MP3 files of songs we're rehearsing. What a pleasure it is to wirelessly connect a phone or portable file player with the above-mentioned dongle—a process that takes about 20 seconds—and stream those files through my system. Yes, the file compression that's been expertly engineered into the MP3 files and the similar handicaps of the Bluetooth codec conspire to make those recordings sound as if they're being heard through a sheet of perforated waxed paper, but it's easy.

The only complaint I have pertains to the 851D's user interface, which I found slightly clunky and needlessly complex. For example, in order to change from non-inverted to inverted signal polarity, one has an unappealing choice: use the processor's front-panel buttons to work through two levels of menu screens, or use a single subminiature button on the remote handset—but in the latter case, one must first toggle through all three options of digital-filter contour. Which is lame. (Incidentally, I share JI's preference for the 851D's Linear Phase filter, and his antipathy for the Steep filter.)

In all, I'm very glad John Atkinson sent the Azur 851D my way: It has been an education and a pleasure. Cambridge Audio's distributor, Audio Plus Services, will see its return, in good shape. But for more reasons than one, they may have to wait until spring.—Art Dudley

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Footnote 1: But in his testing, JA discovered that even TosLink locked to a 192kHz signal.

Footnote 2: The Editor certifies that this is, indeed, a joke.

Footnote 3: It's actually D-sharp to G-sharp: Rawlings usually has his capo on the first fret, as a matter of course.