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With the €1.995 Hong Kong converter the differences operated in the same domain but were more pronounced to bleed into timbre density. The Ark MX+ solo was more full-bodied and sweet. This was clearly shown on Pedro Ricardo Miño's piano on "Bulería con Ricardo" from Anoushka Shankar's new Traveller album, her first for Deutsche Grammophon. The transient focus of the KingRex remained intact to inject more pepper again, here particularly into the sitar's sympathetic resonator strings. What changed was the expansion of this quality into the timbre aspects. The AURALiC solo had more of an advantage than the Zodiac Gold. Perhaps this suggested a truly virtuous USB implementation by Xuanqian and Yuan Wang and their Swiss collaborators?


To find a converter that would be unambiguously improved by the KingRex, might I have to press further down-market? I reached for Burson's dedicated converter, the $950 DA-160 with its ubiquitous Tenor Audio USB chip.

Here the UD 384 gave me clearly more - more image specificity; more articulated soundstaging particularly in the depth domain; more focus; and more hall sound most notably on decays ricocheting off boundaries to demarcate the recording venue. Where the Burson solo is warm, dense, very robust in the bass and analog in the sense of being organic and fulsome, it plays second fiddle on airiness and fine detail to other converters which go easier on its embodiment weight. With the KingRex preceding it, the DA-160 made advances in the catch-all category of 'resolution'. Everything went up a click. Now the UD384 was firing on all cylinders and fully in its game. All it took was finding its level. With the Burson standing in from my choices on hand, I'd arrived. I would predict that in such cases the dominant quality of the KingRex will be its impact on soundstaging and subjective timing exactitude - more space, more precision. This left one question. On what level would its built-in D/A converter operate?

If I'd subconsciously assumed a very basic throwaway or 'starter' affair—something you'd quickly want to upgrade from—I stood corrected. The UD384 solo was surprisingly close to the Burson. The most pronounced difference was in the lower registers. Here the Australian had the greater voltage swing to sound more robust. Tonally it had more black in its color palette. While that did render the KingRex lighter in overall weight, it was far from lightweight per se. This was unexpected. Without having competing über minis of HRT Streamer caliber on hand, I of course couldn't assess how the KingRex might hold up in that field. Given the Burson case, I'd expect quite well.


Upshot. The persistent forum whispers on the upgrade path of external USB/S-PDIF converters à la Audiophilleo or U3 are spot-on if spotty. In the right circumstance such add-on boxes will ratchet up the performance of even quality D/A converters which are already fitted with their own USB inputs. What exactly might be the explanation—better jitter performance; superior isolation from computer noise; other?—remains for the engineers to sort out. What ears alone can determine is that just as 1s and 0s aren't etched immutably in stone as though they were impervious to many external factors, USB inputs are created far from equal. That's quite independent of how upscale of a digital-to-analog conversion or output stage might follow them. It's the old analogy of the premium car with retread tyres.

KingRex has previously shown a real penchant for going far with little and obtaining surprising results from modest ingredients. The latest UD384 appears to follow those precedents. While the nomenclature could confuse by suggesting a digital data output above 192kHz—again 384kHz is possible only through the analog outputs—the price/performance ratio was unapologetically solid and commendable. The thing not predictable is the 'headroom' hidden behind various USB ports. Not all are commensurate with the remainder of their machines. Knowing where that's the case; and whether the UD384 will be the magic cost-effective upgrade... that's where our audio pursuit once again turns into a murky spree of shooting in the dark.


Conclusion. For $479/$189 for the UD384/U Power respectively, this latest offering from KingRex is neither peanuts nor caviar. In the bigger hifi scheme it's simply closer to the former. Given the $950 Burson Audio DA-160's improvability at the hands of the KingRex duo, it seems fair to suggest that $1.000 D/A converters with built-in USB ports should be considered prospective tango partners. And yes it does mean two more boxes (albeit small ones), an extra S/PDIF cable and in case of the U Power recharging. The obvious no-brainer application is an existing legacy DAC which one doesn't wish to part with but which lacks that now de rigueur USB socket. With KingRex you can simply bolt one on. In many cases that will be the smart thing indeed...
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