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Positive Feedback ISSUE 53
january/february 2011


The Neoteric Listener... and the KingRex UD-01 Pro USB DAC and USB Cables from Wireworld, Nordost, and Furutech
by Dean Seislove



Most die-hard audiophiles can't sit still. You watch them sitting there, listening to the latest orbital resolution music download, and you know that the wonderful sound filling the room will soon be displaced by a growing restlessness. The first two minutes, the audio enthusiasts calculate every conceivable variable, mentally measure the soundstage, chart the dynamic range, and feel the fabric of the musical texture with such intensity it's surprising eardrums don't gurgle over from the heat. But soon, the observational chatter subsides and suddenly the incipient twitching to start changing something, anything begins.

Face it, audiophiles are nothing if not a tinkering lot, and that's good because high end audio is a toy with plenty of accessories. Mucking about, jamming in cords and cables, or swaddling rubber feet in sacred stereo shrouds is a matter of course. Meters and screwdrivers and implements of destruction mean that no line stage or power amp is safe from somebody prying it open and sticking his or her big honker where it shouldn't oughta be. Wires, capacitors, transformers, pots for panning, it's all there, just waiting for putterers to move things around, swap materials, fiddle with wires, and do things that tempts engineers to leave in a non-lethal but instructive shock for meddling novices.

...except for DACs. Even the most intrepid mod-ster leaves these alone, because, well, DACs are different. DACs rely on a canon of sampling rates and the unquestioning acceptance of the faithful. My computer says the file is 192kHz/24-bit audio, and who am to call it a liar? Chip manufacturers throw measurements around like incantations to cast spells on those of us who have enough trouble picking the right music format to download. And nobody has invited me to be there when they're changing Sabres and TI chips in the same DAC in the same system with the same file, which makes it pretty tough to make blanket statements about which chip sounds the best. No, I'll let Wolfson, Burr-Brown and the rest of chip set wrestle with link layer controllers and schematics and other things that I can't solve with a pan of brownies and fuzzy bear feet slippers. Besides, my ears don't count so well, so the only way I can decide whether or not something sounds good is to play a buff bag of music and hope that guitar lessons over math camp was the right call.

Which is just what I did with the KingRex UD-01 PRO USB DAC. Employing a Burr-Brown PCM 2702E decoder chip, a low-pass filter, DC servo design, on-board matched, regulated, linear toroidal power supply, and gold RCA SP terminals, the KingRex works hard to justify its $350 list price. The improved power supply, by the way, is the main upgrade from the previous UD-01 model. Capable of sampling rates at 16-bit, 32, 44.1 and 48kHz, the KingRex is designed for users who just want a USB DAC connection to play great sounding standard music files and internet music without the usual audiophile rigmarole. If you happened to have read my column on the HRT Music Streamer II+, however, you know that there are several fine and very reasonably priced options for achieving this goal, the Streamer II+ and the devilsound DAC chief among them, so where does that leave the UD-01? Very nicely, indeed. as we'll see.

The excellent Streamer II+, alas, has long been returned to the manufacturer, but my trusty devilsound Version 2.1 is still on hand to digitally duel this new digital-to-audio converter challenger. The contrast between the two products points out just how hard it is to find the DAC bed that feels just right. Each has an excellent presentation, but neither sounds the same. Both the devilsound and the KingRex produce a large soundstage and offer up enough musical detail to keep you happily amused, discovering new qualities hidden in your favorite music. The devilsound trumps the KingRex in producing a really wide, slightly more forward and resolving delivery of vocals and instruments when listening to most internet radio stations and high-impact music. But bigger and louder isn't always better, and there is definitely much to be said for the KingRex's more nuanced approach to bit taming.

Anything that has even a bit of an edge or distortion is magnified by the devilsound, and though this is something that I had detected before, only in contrast to the KingRex did I find it objectionable. David Sanborn's saxaphone on Bowie's David Live album, for example, is unquestionably one of the best horn performances in rock n' roll this side of Bobby Keys. Direct comparison from the devilsound to the KingRex, however, shows just how unappealing saxophones that are too etched and grainy can be in hard driving rock n' roll. The UD-01 PRO's ability to soften the contours of the notes without muddying up the whole thing made for a very enjoyable listening experience, while the same performance via the devilsound gave rise to listener fatigue, not something that usually happens with one's favorite music.

And, really, it's the smooth, relaxed presentation that makes the UD-01 PRO a viable choice for listeners who can't stand any semblance of digital edge in the mix. Jeremy Camp's wonderful Live Unplugged album contains all the beauty and challenges of a superb live recording. Hot mikes are necessary to define the performance and the rest of the mix, but that top end on vocals and instruments can wear you out like sitting on a hard chair next to the stage monitor if your system skews towards the sharp, dynamic, and bright. The KingRex DAC did a nice job presenting the illusion of depth and space between performers, while taming some of the excesses of the live recording. Similarly, streaming "Angels We Have Heard On High" by Philip Wesley, there was a tangible impression of space and airiness as the beautifully rendered notes of the piano decayed into the atmosphere.

It's a very different sound than you get from the devilsound (which has terrific wide open pop, but tends towards graininess in some instances) or the HRT Music Streamer II+ (musical, like the KingRex, but more balanced and resolving). One important caveat when comparing these three products, however, is the fact that the devilsound v2.1 DAC has its USB and RCA cables attached. Conversely, the HRT model and the KingRex UD-01 require you to supply both USB and RCA cables, which enables you to fine tune the sound (albeit at a cost) in a way that the devilsound's design precludes. Moving from a pair of Kimber Hero interconnects to Harmonic Technology Magic Link IIs to Stereolab LS-700s, respectively, progressively widened the view of the KingRex's sonic image. The sound changed, but it was primarily in the ability to discern the details more completely. It's not as if the Stereolab interconnects suddenly made the UD-01 PRO explode like the devilsound or envelop the room like the HRT II+, but there's no doubt that soundstaging, microdynamics, and tonal variations became more pronounced in the KingRex because of the better cable being used. And it would be fair to say that pairing the UD-01 PRO with the right USB and RCA cables might make a difference in whether or not you like this DAC in your system. Naturally, this opportunity to improvise might appeal to those who love to monkey around with tweaks and cables to improve the sound. Now, for those who want to take it a bit further than necessary (and isn't that high end audio in a nutshell?) you can always start collecting these low-cost DAcs like phono cartridges and rival the zealotry of the vinyl brigade, but that's a quest you'll have to undertake for yourself.

All I know is, the UD-01 PRO will appeal to those who desire a warmer, rounded sound from a DAC, or to those with systems that could benefit from these qualities. Or, if you just want a good sounding box to get music out of the computer and be done with it, this is a fine option. The more I listen to the sweetness of the KingRex's presentation of music, the more I appreciate its understated handling of digital files. The KingRex UD-01 PRO is a very musical and sensibly priced digital-to-audio converter for the right system, and an easy purchase for first-timers and veteran DAC collectors alike.

Retail: $350


USA dealer

A Note Concerning USB Cables...

When my editor handed me the KingRex and three USB cables, I thought he was taking advantage of my well-known gullibility for all things audio ("Dean, you'll need all three cables for this DAC to handle low, mid, and high frequencies"). Turns out, he thought that auditioning the KingRex with several USB cables might prove instructive. Kind of risk, actually, as I have a well documented insensibility to the virtues of many, many high end wonder products. More than once, I've been in a packed room where a product rep is extolling the miracles of some wire, disk, or box festooned with a thick technical white paper and an even fatter price tag. When the demonstration is over and the rep asks if we've all heard the amazing difference, the crowd wags their heads in assent like peppy chihuahua dogs, while there I am, a solitary Butthead, muttering, "Uh, no." Hey, if you hear it, you hear it--that's the only measurement that matters--but I'm not paying hard currency unless the product works outside the showroom. Anyway, I am proud to announce that all three of these USB cables not only work, they each possess a perceptively identifiable sound for this listener, at any rate. Duly noted, of course, is the fact that it's the old window-or-prism argument: Does the cable relay the sound of the DAC, or does it add its own sonic imprint? And that was my dilemma when evaluating the efficacy of all three cables, so I just decided that this is how each pairing of DAC and cable sounded at this moment while amplified by Virtue Audio Sensation and articulated by Nola Boxer speakers. All non-internet radio selections are iTune lossless files using Channel D Pure Music.

First up is the Furutech GT2. Furutech's website tells us that the GT2's feature "24k Gold-Plated Nonmagnetic USB 2.0 Connectors, a Silver-Plated a (Alpha) OCC Conductors and a special-grade high-density polyethylene insulation/dielectric." I don't know if these precious metals are the cause or merely a visual embellishment to the sound, but music produced by the KingRex and Furutech pairing had a solidity and presence that eluded the other cables. There was no trace of that irritating hard digital edge on horns or snare drums and the like when using the GT2. Given that the KingRex is a pretty suave customer in its own right, you might think that a cable with a leaner profile might be a good complement, but such was not the case. Having only one DAC on hand, I don't know if the retrieval of low-level frequencies or the full reproduction of horns (to cite only a few examples) was the sonic property of the GT2 or an accurate rendering of the KingRex UD-01 PRO, but whatever it was, it sure sounded full, rich, and expressive. The depth and substance of the music when using the Furutech USB cable was extremely seductive, and I could discern that this is a cable designed for long-term listening enjoyment.

Second in the line up is the Wireworld Starlight 6 USB cable. Possessing "oversized 24 gauge silver-clad OFC conductors and a proprietary low-loss ground path," [mfg. website] this cable offers a remarkably open and transparent delivery of the music. The Wireworld impressed me by being the most "natural" of the three cables. Instruments and vocals were nicely balanced, in that I never felt that any frequency range was artificially favored over another. The Starlight 6 is also a winner for helping the KingRex deliver a pleasantly detailed and resolving sound. Listening to Beth Orton's , the Wireworld Starlight 6 gave remarkable clarity to walking bass lines, steel string accents, and Orton's signature vocals. This added precision never became strident, even while playing noisy passages in my mp3 downloaded-on-a-whim file of Mogwai's "You Don't Know Jesus," from their excellent live album, Special Moves. Plenty of synthesizer and feedback (among other noise) coming to a head in this track, yet the Wireworld made listening to it all something to be savored and not skewered. The Wireworld Starlight 6 USB cable is neutral in the most laudatory sense of the word. Again, I only had the one DAC to judge by, but I suspect that the qualities evidenced in my time with the Starlight 6 make it a natural fit with a wide variety of DACs at many price points.

The final cable to be paired with the KingRex is the Nordost Blue Heaven USB cable. Here, we have "a high-tech, micro-mono-filament design" [mfg. quote] from the venerable Nordost company, a manufacturer famous for expensive, ultra high performance cables. Easily the most resolving of the three, this is a blazing fast cable that can pounce on a note's attack and chase it to the final reel in even the most demanding tracks . Be forewarned, though, this is a less forgiving sound than either of the previous cables, one that gives no quarter to poorly recorded music. The Blue Heaven produced a leaner sound than the other two cables, but on tracks of high quality this ability to see everything but the engineer in the window in a recording is worth suffering the occasional clunker music file. Sadly, much of what I listen to is noisy as all get all even in the best of circumstances. Led Zepplin's "Immigrant Song" from Led Zepplin III (original CD release) is typical of what tumbles out of my iTunes genius mix (it must refer to the programming, not the library). Hearing every broken stick is stupendous, but listening to this digital file rendered so ruthlessly unforgiving at the only volume I'll allow this song to be played at is more than I can take for very long. Flanger's "So What" from the album Midnight Sound, however, sparkled and swung in 5/4 time (when intended) because every detail of the track, such as the reverb/ delay applied to the Fender Rhodes electric piano and Vibraphone, was fully evidenced. If the components and recordings are of high quality, the Nordost Blue Heaven USB won't disappoint those who favor speed and detail. Don't mix it with the cheap stuff, though, and you'll be much happier.

Furutech GT2 USB cable
Retail $114

Wireworld Starlight 6 USB Cable
Retail $100

Nordost Blue Heaven USB Cable
Retail $250