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Mounting evidence from forum-posting owners and colleagues like John Darko of DigitalAudioReview.net.au reinforces growing personal suspicions. In many cases outboard USB-to-S/PDIF boxes can improve the performance of D/A converters which already sport their own—and presumably high-quality—USB data processing. This rather spits in the face of my personal preferences. There I'd rather have fewer boxes and cables and less clutter from clever integration. But lady reality would remind us all. She rarely conforms to our preferences. Touché. Ouch and the works! To investigate how the battery-powered KingRex might factor into this context, I pulled out my Antelope Audio Zodiac Gold with Voltikus power supply; the AURALiC ARK MX+ still in from its review awaiting the arrival of its Taurus mate; and the latest Burson DA-160.

But first a quick glance at the 192kHz-plus catalogue of high-resolution software. HighResolutionAudio's website at the time of this writing showed all of seven titles at 352.4kHz, 57 at 192kHz. Their list of converters capable of playing the former included eight - the Zodiac Gold; M2Tech Young; Playback Designs MPD-3 and MPD-5; and four models from MSB Technology. Whilst their website obviously isn't the only purveyor of hi-rez software, these figures are representative of the fact that we're presently at the very beginning of the so-called Studio Master phenomenon. How it will proliferate; and whether it will eventually extend across the divide of 'audiophile' fare into more popular music - this remains to be seen. Components like the KingRex would simply have us ready for this future in case it happens on a scale relevant enough to include music we actually care about.

Both AudioMidi's and PureMusic 1.82's Audio Setup windows confirmed the KingRex UD384 to be capable of 352.8/384kHz data. To OSX Lion the USB receiver looked fully ready even for the confirmed-as-missing 352.8kHz. This suggested that the limitation wasn't in the KingRex chip's input receiver (which the computer 'sees') but in its converter function (which it doesn't).

To test whether the KingRex would actually pass 384kHz data as promised, I needed to start my audition with the Zodiac Gold. None of my other converters can presently process such signal without forcing PureMusic to first downsample it. With the above windows set to 384kHz and PureMusic's upsampler engaged to hit this target rate, data was shown as streaming out of my iMac at that rate. Alas the Gold failed to lock to this signal. Meanwhile all sample rates up to and including 192kHz locked without any issue. Since the UD384 bills itself as 384kHz-ready, I was both surprised and disappointed.


To confirm that I wasn't erroneously blaming the KingRex, I next ran the Zodiac Gold USB direct. Voilà, 384kHz (and 352.8kHz) played without any issues now. What this meant was that the KingRex—at least at present—could not pass data above 192kHz as its name promises. Perhaps a firmware update was required?


As Christine Wu explained, not. "If you are using the UD384 directly, its DAC will pass 32bit/384kHz just fine. If you are using the UD384 to pass the digital signal to your Zodiac however, then yes it will not be possible to go beyond 24-bit/192kHz. That's due to the inherent limitation of S/PDIF. If you wanted to output 32/384 to your Zodiac converter, our UC192 could do that. After the firmware update the UC192 upgrades itself to 32bit/384kHz DDC via its I²S output (S/PDIF& AES/EBU will still be limited by the 24bit/192Khz spec)). You could download the UC192 DFUtool, firmware and driver but I checked the rear of the Zodiac Gold and it lacks an I²S input. This makes 32/384 transmission impossible. My apologies that in our emails I sent you our old specification sheet where I hadn't yet noted this 32/384 limitation via our S/&PDIF output. The current sheet makes proper mention of it."

Comparing Redbook material at its native 44.1kHz rate—99.9% of my collection—the li'l KingRex proved to be quite the performer by not 'sinking the ship' when I switched it into the signal path. Against Igor Levin's USB implementation it came in second by sharpening transients more. On piano this could introduce a whiff of the glassy. On percussion it accentuated attacks out of the mix more where the Zodiac Gold was smoother though not one iota less resolved. I've come to recognize one artefact of higher jitter as sharper needlier edges and spicier attacks. At first this might suggest more precision as though the staccato/legato contrast ratio had gone up. Longer listening simply shifts this impression. This type of prickly sharpness is actually less natural and organic and as such less agreeable over the long term.

Very much to the KingRex's credit however this difference was quite small. Its low price was not concomitant with dragging the Zodiac's performance into a patently lower league of performance. It simply meant that a critical listener in a resolving system would have to admit that the €3.495 Antelope converter was already fitted with a USB solution superior to what KingRex has packaged into its tiny two boxes. How would this assessment translate to the Ark MX+ with its Swiss Archwave processor running USB transceiver duties?
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