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The Hydra X+ arrived double-boxed via small EMS package to have Swiss Post complete the delivery. Ensconced in blue foam caps there was the Romanian black box and a small battery charger with standard 3-prong power IEC to take normal power cords, not figure-8 jobs. Because this device is capable of 384kHz PCM transmissions, I had initial struggles with PureMusic 2.0.1's upsampler into my 192kHz-limited Metrum Hex.

To my ears that converter sounds best with 176.4kHz NOS-style software upsampling. Despite setting AudioMidi's and PM's target range to 176.4kHz right off the bat, my software player kept stubbornly resetting itself to 352.8kHz as the x 2 rate the Hydra X+ really was good for. Needless to say my Hex couldn't lock to such signal. It blinked incessantly in protest. I could easily defeat PureMusic's upsampler for instant 44.1kHz gratification. But I was just as stubbornly intent on my proven 176.4kHz mode. After a few PureMusic relaunches I finally locked it. The Hex connected via my customary purple 110Ω AES/EBU van den Hul leash.

To avoid having my cables move the light box, I topped it with one of my Artesania Audio mass dampers slash RF shield discs. Now my only practical miff were the dual-sided connections. For cleaner cable routing this mandated a sideways installation and thereby no line-of-sight visibility of the operational LEDs. Hey, we gotta complain about something.

Sonically my $1'350 two-box SOtM ride with super-clock feature had no definitive advantage. If there were any differences (depending on track I felt quite uncertain), they operated solely in the domains of relative soundstage depth and subjective speed. Sometimes the Hydra X+ seemed to have me more aware of a bit of added stage depth. At other times and obviously without any change in pitch, I thought the SOtM was the more relaxed to play it marginally slower. Because these observations were so subtle, ambivalent and as such unreliable, I decided to write them off. For all practical intents and purposes, these components were ideally matched equivalents and as such perfect stand-ins. Given the price offset, for many Rockna would be the obvious choice. It also passes 32/384. For those who hate black, sideways cable routing and don't do anything above 24/192, SOtM would swing the vote despite the added cost.

Compared to Metrum Hex direct as the type of comparison potential buyers would find most relevant, the Hydra X+ improved what I thought of as timing. This manifested most notably on transients as the initial rise of sounds from silence being better defined. During complex passages this led to greater definition. It directly assisted better separation as the ability to follow many overlaid intertwined lines without suffering shadowing effects of partial obscuration. Lastly, minor tendencies for image bloat disappeared. This action is a very subtle shrinkage or firming up that comes from reduced micro blur. Very attack-driven crisp music makes it easiest to first hear the improved leading-edge definition. Think percussion and plucked strings. Gentle legato-rich recordings or those where microphones stood at a distance to capture more mixed-in reflections take steps back from this quality. It still applies of course but less overtly so.

The same goes for programmatic complexity. Girl+guitar fare is so non-challenging on complexity that you won't benefit from improved separation unless you started out very poorly indeed. In short, depending on how good the USB transceiver of your DAC is, an add-on external USB bridge will make less and less to no difference. In my financial comfort zone, I've simply not come across a DAC yet which couldn't be at least subtly improved by the best USB bridges à la Audiophilleo or SOtM. Now the Rockna Audio Hydra X+ adds itself to that list. To quantify the level of improvement I experience with adding a superior outboard USB bridge to DACs of Metrum Hex, AURALiC Vega or Eximus DP-1 caliber, I'd call it rather smaller than swapping complete cable looms as I did for recent reviews of Absolue Créations and Arkana Physical Research. Complete swaps of cable sets (interconnects, speaker cables, power cords) can affect tone and colour density, dynamics, body, bass weight and shift the transient/bloom/decay balance. Except for the last, in my context those qualities don't really apply for today's type of device. If you began on a lower tier of converter quality, I'd imagine that to become more inclusive.

Having their particular range of address be narrower and more focused doesn't invalidate an external USB bridge at all. But it's also fair to say that more than many others, it relies on the rest of your equipment for magnification. Here time-confused big multi-way speakers with poor impulse response would seem handicapped by design. The same could apply to slow cuddly valve amps of limited bandwidth, heavy THD and inherent treble phase shift. With systems dialled for speed and lucidity, upgraded USB converters come more fully into their own and now are well worth investigating. Given expected deltas of performance, I'd simply attend to a proper cable loom first. If you've heard what a well-engineered equipment rack can do, that's more the general type or flavour difference you'll obtain from an external USB-to-S/PDIF box. The remaining qualifier is obvious. What's built into your current DAC must leave sufficient room for improvement to be relevant. Against that proviso the Hydra X+ strikes me as a sensibly priced high-performance option for DACs up to €4'000. Of course you have to figure on a quality digital cable and whatever its cost might be to complete this proposition.
... more when the WaveDream converter arrives...
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