Audiobyte HYDRA X+ LiPo battery-powered USB converter


A buddy in Melbourne and I have been discussing USB converters of late. (No, his name is not Barry). Mark seeks a solution that’ll bring him a noticeable uptick in tonal colour and acoustic mass. One might loosely refer to this as presence.

This writer’s direct experience with some of the more established players in the budget USB converter field – Audio-gd, Wyred4Sound, Resonessence Labs, Audiophilleo – suggests that any of these would be meet Mark’s needs. The trick for this customer buying sight unseen is knowing the degree of improvement. For him it’s a matter of reconciling money drop with performance lift. Like many listeners, he’s not only asking which USB converter will maximise bang for buck but which is best?

With our first ‘B’ word we hit a subjective descriptor wall. The Audiophilleo and Concero HD both rate equally highly in my book but for different reasons. The Audiophilleo is drier and perhaps has the edge on detail retrieval; the Concero HD is wetter and more fluid. Only during a brief two-week on/off dalliance with the Audiophilleo’s PurePower battery appendage did I feel that I was getting the best of both worlds. Only when moving up to the SonicWeld Diverter – another short-term loaner – did I best the AP2 + PP.

Now we hit our second ‘B’ word: batteries. One might presume that in bypassing the USB 5V power source that a lift in sonic performance is a given. Yes…and no.

Vinnie Rossi at Red Wine Audio has grown an entire product line from battery powered devices and this time last year I pointed him to one of the many portable battery packs used for charging mobile devices as possibility for slipstreaming 5V into the DAC’s USB port via an Elijah Audio cable.

Rossie replied: “Stay away from that! Why? In order for it to output 5V, they use a switching regulator because it is most efficient and barely makes any heat (so it’s happy in its plastic enclosure). But it totally defeats the purpose of using a clean battery solution, as it is very noisy.”

The lesson? Not all battery power is born equal. Battery packs introduce their own noise profile – one cannot assume that the deployment of battery power automatically equates to lower noise.

Going DIY necessitates a keener eye for what lies beneath the casework and had me looking back toward commercially marketed solutions. And initially it appeared as though Philip Gruebel, SOtM and (to a lesser extent) KingRex had the entry-level, battery-powered USB converter market to themselves.

A Google search for further options pointed my Chrome browser to Romania. Audiobyte’s HYRDA X+ (AU$1325/€699) applies Crystek clocking to data streams for output via AES/EBU, coaxial, BNC and I2S which means turkey talk with PS Audio and other DACs that opt for HDMI connectios. An ARM processor marshals the USB input whilst a Spartan-6 FPGA handles the output conversion and allows for DSD compatibility.


The point of difference for Audiobyte? Lithium Polymer (LiPo) battery power that the specifications sheet describes as “low noise battery technology”. Similar to Rossi’s Red Wine Solutions, the HYRDA X+’s battery charging is an automated process with mains juice sourced via a SMPS wall wart.

Pricewise, the HYRDA X+ pitches right into AP2 + PP territory – AU$1499 down under. That’s the reason its gets a news nudge here. Battery options like these often find favour among power purists and/or those seeking what the marketing rhetoric might refer to as ‘best in class’.

Confounding the issue is one of application: which DACs find themselves tickled by fancier USB conversion? Spending considerable listening time with PS Audio DirectStream DAC these past few weeks has exposed it as stubbornly resistant (mostly) to the Concero HD’s charms. Extracting deltas from a USB cable comparison proved similarly difficult. From a reviewer perspective this is problematic. From a listener’s perspective this is a dream realised.

Rowing downstream to the likes of the Schiit Biftost Uber sees differences laid out more plainly. The AURALiC Vega gives up the effects of diet changes whose magnitude sits somewhere between the Bifrost and the DirectStream but closer to the PS Audio.

Oversimplifying for the sake of argument it seems the more you spend on your D/A converter, the more likely it is to feature circuits that provide considerable immunity to jitter and electrical noise. That said, below the $3k marker, empiricism speaks more loudly of an ongoing need for good USB conversion; and Romania’s Audiobyte have stepped forth with another interesting option for our friend Melbourne Mark to consider.

Further information: Audiobyte | Audio Heaven

Written by John H. Darko

John lives in the NOW + HERE = NOWHERE. He derives an income from the ad revenues of DAR. John is also an occasional staff writer for Stereophile, 6moons and TONEAudio.

Twitter: DarkoAudio
Instagram: DarkoAudio
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  1. Higher precision USB conversion has needed a particular emphasis on supplying extremely clean and precise power at crucial points in circuit design. I learned that by watching Steve Nugent evolve his Empirical Audio products using Hynes regulators at critical points. I used one of his older mid level Off Ramp 3 USB-S/PDIF reclockers until more modern and much less expensive hardware beat it. I expect his newer pricey USB products to be right at the top of the best available.

    Having a good time with the DirectStream? Looking forward to your review. I’d go straight to one if I had $6k USD to throw at a DAC, but it’s overkill for me at this stage anyway. I’m stuck at a Bifrost Uber level with a proper balance of equipment and the Bifrost is certainly no slouch. It’s fed by an external USB-S/PDIF box with a CM6631A chip and powered through the downstream USB connection by a hifi ADuM isolator and a linear wall wart. Best combination I’ve had in my meager system short of spending a bunch of money to go to another level. The external CM6631A with ADuM isolation performs better than the ADuM on the similar Bifrost internal gen 2 USB.

    What did the Hydra X+ do for your Bifrost Uber?

    • Hey Newk, I don’t have a Hydra X+ but given Schiit’s above average USB implementation I’d wager the improvement wouldn’t be as pronounced as when the same USB converter is applied to rivals.

      Sounds like you’ve hit pay dirt with your setup. Yes, the DS is better but – as you say – it’s a LOT more coin.

      • Wait, is that the same DS DAC that upsamples everything to DSD? If so, you’re a luck lad. Supposed to be an excellent bit of kit.

  2. I reviewed this box. It’s directly competitive and on par with SOtM’s very best two-box super-clock’d 24/7 power-cycling battery device but less money and capable of 384PCM and DSD128 (the SOtM which I own limits at 192kHz).

    I owned the Audiophilleo before the SOtM (albeit without Audiophilleo’s optional battery supply) and thought the SOtM a step up. I’ve also tried the Concero and the April Music U3. Out of this bunch, SOtM and Audiobyte to my ears come out on top.

    The one thing I didn’t love about the Audiobyte were its transverse i/o. If you park the thing with the status LEDs in front, you’ll also have a cable exiting in the front. If you want a cleaner look, you gotta place it sideways and have cables entering and exiting left and right. I prefer all the wires on the back and a clean front. But that’s a minor nit…

    • Thanks Srajan – I was hoping you’d chime in on this one as I did see Fred Crane had teed up a unit for you. Good, low noise battery power acts as a performance enhancing drug for USB converters as you’ve found with the SOtM and Audiobyte and me with the Pure-Powered AP2.

  3. Another USB to S/PDIF converter that competes admirably with the Hydra is the YellowTec PUC2. Some reviews indicate that it provides a more detailed presentation than the Hydra.

  4. Your comments and quote from Rossi jumped out at me because I recently fiddled with a neat 5v battery into my bel canto mlink/Bifrost setup. Here’s an excerpt from my notes:

    “Listened for an couple hours and it was fine, but there was a bit of metallic sheen and “lightness”. Went back PC direct to bel canto and the difference was greater than I thought. Sheen gone, more round, more meat, relaxed, yet delicate and detailed with great attack. No need for further exploration here.”

    As always John, your reviews are enlightening and entertaining.

      • That’s my best description of what I heard. It would be easier if I could post a pic, but the split cable is, I think, a cheap variation on the elijah you mentioned, taking a $35ish Radio Shack battery for charging mobile devices plus my Wireworld usb for data.

        Just going with the Wireworld from PC usb to the mlink sounded better to me as described.

        Of course, the degradation could be the battery, the split cable and extra connectors, the quality of the connectors, or some combination.

        My expectation was that I wouldn’t be able to hear a difference, so I was surprised at the result.

        • …but the point is: batteries don’t automagically make things sound better. It depends on the battery and – as you say – cabling used to connect it all together.

  5. +1 for the Yellowtec Puc 2 lite.
    Its a fantastic “under the radar” USB to AES/SPDIF converter.

    Its made for the pro audio guys not hifi nuts 😉
    As such it doesn’t command an over inflated “audiophile” price.

    The Puc2 subjectively improved on my Audiophileo AP1 running clean 5vDC linear power injection. The Puc2 lite plays best with Windows and OSX, Linux users should look else where.