Black Holes and Revelations: KingRex UD384 DAC and UPower PSU


The new KingRex UD384 DAC delivers music with an absolutely black background I have yet to hear from other DACs. From the first moment I tested the UD384, even with a humble HeadRoom Micro and Shure SE215 combo, I realized that this DAC has got the lowest noise level and the blackest background that I’ve heard in a while. I’ve listened to a lot of great DACs with black backgrounds, but they are not this black. The KingRex is so black, your monitor can’t reproduce it even if it was turned off.

The Black Background

Imagine an empty concert hall in an empty building in an empty town. The moment somebody walks in to that hall, you know that the sound of his steps is going to be very distinct, moderately loud, and crystal clear. If we were to take this guy and drop him in New York’s Fifth Avenue or Tokyo’s Shinjuku district, with thousands of other people walking on the same road, you can imagine that his footsteps will simply disappear, even if he tried stomping his feet twice as hard.

We’re talking about relative noise levels here. Another example is when you happen to be up at 1AM at night, when things are so quiet that you can hear the second ticking on the clock very clearly. If you turn off the A/C for a moment, close all doors and windows, and get under your blanket, then even the sound of your breath would suddenly sound very loud. It’s not because you’re breathing harder, rather because the relative noise level is so low.

This is what a black background is all about. When the relative noise level is so low, the slightest noise so clear and distinct, without having to boost treble levels. The result is crystal clear sound even at very low volume levels.

I’m totally in love with the KingRex, even not considering the superb 32/384 driverless USB capability. The sound is extremely natural, no treble boost, no fancy tricks, just simple pure black background. Vocals and instruments are incredibly distinct and real. There is no shrillness, no dryness, no nasty elements whatsoever in the sound. The tonality is quite dark, but then again there is no difficulties in seeing the details in the recordings because of the black background. Of course it’s recommended that the KingRex be paired with a good transparent amp like RSA’s Dark Star or Woo Audio’s WA5 so you can hear all that blackness in the soundscape. But even if you’re only using a relatively entry level amplifier like the HeadRoom Micro Amp or JDSLabs’ O2 amplifier, the blackness of the KingRex is still very evident.


I didn’t really test the UD384’s ability as a USB to S/PDIF converter, but my friend Drew immediately bought the UD384 and sold his Empirical Audio Offramp Turbo USB to S/PDIF after spending a few days with the KingRex. His comment was: “an incredibly black background”.

Minus the UPower

The Upower is a rechargeable, 2600mA battery pack designed to supply clean power to the UD384. But say your budget only allows for the UD384 without the UPower, what kind of a sound will you get? A weaker low bass is the first one I notice, though it still hits quite low. More subtle changes, however, includes a less distinct instrument presentation and body on the soundscape, as well as smeared transients though just a tiny bit. Without the UPower, the UD384 will still take on the DACPort LX any day of the week (not to mention the added 24/384 resolution and USB to S/PDIF converter function which the DACPort doesn’t come with), so this is still a very good DAC. But with the UPower, the UD384 suddenly is playing in a $1,000+ territory. Totally awesome stuff for the money.

I’m actually not such a big fan of the Ipod sized form factor. You have the USB cable coming in from one side and the RCA out from the other side. Then you have the power cable coming out from the Upower and into the UD384. Since this is a USB DAC, you’re bound to have it placed close to your laptop, and all that cables, especially the DC power cable that connects the UPower makes the KingRex pack looks like a messy piece of gear on your work desk. I would rather KingRex offer the whole package with the UPower in a one box package, perhaps a Schiit Asgard size enclosure, and even throw in a decent headphone out in the box as well. But regardless of how messy it is, still I’m using it every day of the week simply due to that blackhole-like dark background.If they had put the UD384 in a more convincing package, it probably can sell for a good $1,000 and still be a good buy at that price.

The UD384 is so amazing I’m intrigued to give their headphone amplifier a try. Who knows, it may be another winner.


Gear used for review:

MacBook Air, Audirvana+, Fidelia, Amarra, Ray Samuels Audio Dark Star, Woo Audio WA5, Minute 45, numerous headphones and other amplifiers.

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  • Lol at the name, I sure do love Muse and it so happens I am listening to them this very moment as I write this. 🙂

    Anyways, great review, Mike!

    • Thanks!
      Black Holes and Revelations was the second thing that came to my mind when thinking for a title for this review (the first one was not so good). 😉

      I thought that phrase goes well with the concept of the review. 

      • Anonymous

        Don’t kid yourself Mike, you chose it because you copied their Logo…Tsss…

        • We’re supposed to be partners man.

  • John

    read this and got me thinking… what’s more important for sound quality: an amp, or a DAC?  

    • Anonymous

      I’d say both, but mostly the source, because if crap goes in your amp, then crap will go out

    • The theory of course is that a good source is the most important part. However I find that in practice it is not always the case.
      For instance:
      a. When you’re playing music with bad recording quality, a good DAC would not help. What would help is an amplifier that can smooth out the bad recording (yes a non-neutral amp). b. With some people it’s easier to pick up the effects of an improved amp, rather than an improved DAC.

      • John

        i forgot to add the disclaimer ‘everything else being equal, ‘ but i understand what you’re saying.  i have a layman’s understanding of how a DAC and an amp work, but i wish i knew more of how they each affect sound quality.

        • Perhaps the simplest explanation for that is that a good source gives you a better rendition of the music. More realistic vocals and instruments, better feel of the venue of the recording among others. A good amplifier most importantly should be to give you more power to turn up the volume louder. But some of the improvements of a good DAC can also be present in a good amplifier.

  • Maxime T

    Hi Mike.

    How good is it compared to the Audio GD Ref 7.1?

    • Maxime,
      We’re looking at two different DACs here, both very good although the Ref7.1 is $2,000 I don’t think a comparison is totally out of place in this case.
      The Ref 7.1 is very impressive in recreating soundstage and the ambiance of a live recordings. Micro details are superb on the Ref 7.1. With the KingRex, it’s a slightly different presentation. Both are dark tonally, but the KingRex makes instruments stand out due to the black background, where with the Ref7.1 is not as black. So you get a different effect here. Individual instruments sound more distinct on the KingRex due to the black background, where on the Ref7.1 you get a better picture of the overall recording, the venue, the ambiance.

      • Maxime T

        Thanks Mike, I get your point.

  • Hi Mike, how does UD384 standalone compare to music stream II+?  Would you recommend it for monitor speakers? 

    How much is it? Can’t find any info on it.

  • Anonymous

    How does this compare to the Rein Audio X-DAC?

    • Hi but sorry I’m afraid we can’t give a comparison because Lieven did the Rein review and I (Mike) did this one. 🙂

  • Think about it for a second. One guy writes a post arguing that it doesn’t really matter. On the other hand of the spectrum everybody else you have: – Recording engineers working in high bitrate and sample rate
    – Labels releasing high bitrate and sample rate files
    – D/A chip makers producing higher bitrate and sample rate chips (but this can be a conflict of interest — so they can keep selling more advanced chips) – Software engineers writing their software to accomodate high sample rate files
    What do you think?

  • armydicked

    How would the DACs in this unit stand up to, say a pair of Dual ES 9018 Siber 32 bit DACs as employed in the $1,000 Oppo Uni Blu Ray?

  • sin yee

    Hi Mike, please comment on this set-up:

    Onkyo nsd1 -> kingrex ud384 -> Apex butte

    or do you have a better dac recommendation? thanks

    • Sin Yee,
      You can’t hook up the UD384 to the Onkyo. The UD384 is USB only, need to put a laptop in between.
      Ipod > Onkyo NDS1 > Laptop > UD384 > Apex Butte


      Ipod > Ipod Dock Cable > Laptop > UD384 > Apex Butte

      • sin yee

        Thanks,  am looking for a Dac to upgrade my setup. Would a digital transport like onkyo to a dac be good or it’s more advisable to use laptop as source? And what dac would you recommend? I currently own the Apex Butte amp.

        • Sin Yee,
          I mostly use my laptop these days, since most of the newer DACs are USB.

          • sin yee

            ok, what then do you suggest, pairs well with Apex Butte? As my desktop set-up.

            • The headphone, you mean? Ouch.. well I like Senns.. start with either the HD600/HD650.

  • Hi Mike
    Which do you prefer – dacport lx or ud384 (without the UPower)? I need really transparent dac for my violectric v100 and Hifiman He-4. Not warm

    • Without the UPower, I’d go with the LX as it doesn’t require a separate supply.

  • amigastar

    lovely review, mike.
    i got one unrelated question though, is there any chance or plans that you review the Audiolab M-DAC since i’m personally interested in this DAC? the kingrex sounds also very tempting but its only usb and i don’t know what the future holds if i need some more connections. i know there are already reviews but i don’t know if i trust what hifi so much as you.

    • Thanks for the trust!

      I need to get the Audiolab and listen to it first, then I can tell you how the two compare. 🙂 Sorry about that.

  • Trent_D

    I was just curious since you didn’t mention it in the review. Does the UD384 offer an improved soundstage over the dacport lx?

    • Yes with the UPower. Without, the improvement is quite small from the LX though still the UD384 has the blacker background, but less depth than the LX.

  • UD-384 vs. Centrance DACmini ?

    • Comparable technicalities, the Dacmini being brighter and more forward, the UD384 darker and more laid back. Cleaner sound and blacker background on the UD384.

      • UD384 won my heart then 😉

        • You’re welcome.

  • Hey Mike,

    This is looking good for my AKG K550. Ive always been looking for a blacker background. If you can suggest a portable amp with good instrument separation and good sound stage depth/width, I will be golden.

    • Among the recent amps that I’ve reviewed, the ALO International seems to have the blackest background. Instrument separation, soundstage depth and width are pretty good though not the best.
      If you want the biggest soundstage and depth, the Portaphile 627, but background is not that black and the sound is quite grainy.

  • Hi Mike,

    one question that’s been bugging me. can i leave the DAC on for days? it doesn’t have an ON switch so i’m a bit hassled by the fact that i have to stick the power on everytime i use it and unplug it everytime i’m done.

    • I’ll leave it on for days, yes. If that bothers you, get an AC-strip with an switch.

  • Eyal Sade

    Yulong D100 vs UD384+power ?

    • Sorry haven’t tried the D100.

  • Rogier Schreurs

    This is one impressive piece of equipment folks! It is revealing, detailed, neutral, and yet so flavorful. I haven’t tried a lot of DAC’s and even less desktop models, but this is the single most impressive one I’ve listened to thus far!. Blows the iFI Micro iDSD straight out of the water and don’t even get me started on the Microstreamer/Explorer/Dragonfly bunch. Most uncanny how good it makes the lesser files sound

    • Dave Ulrich

      It would be a fun DAC to put head to head with the Resonessence Labs Concero HD

      • Rogier Schreurs

        If I’m ever to run into one, I’ll try to compare. This is an incredibly neutral dac though; whatever you drive it with, that’s what you’ll be hearing. DT770 AE is still massively fun and sweet when paired up, Fidelio L2 is still… well um very L2-ey with it, haha, but with added resolution and blacker backgrounds.

    • Rogier Schreurs

      I bought a new MacBook yesterday (OSX Yosemite), but my UD384 just won’t play anything coming out of it. The computer recognizes the DAC and I can see it in Audio/Midi too. But the volume sliders are all down to zero and greyed out in the configurator. It does the same on my dad’s Yosemite MacBook. Still works with my older Snow Leopard driven MacBook, though. Does anyone how to make the UD384 work on OSX Yosemite?

      • I can’t get to this right now (I have a new Macbook Yosemite), but I remember having that problem too. All I remember right off is having to play with the volume controls in a couple of places, switch the target for sound a couple of times, and restart the computer a couple of times. There’s a good probability you’ll find the solution. If not, I’ll check some more.

        • Rogier Schreurs

          Hey Dale, thanks for the quick reply. I don’t know how, but it suddenly started working all on its own. I tried a lot of things in the beginning and nothing happened, then later in the evening after having done something else I connected the DAC again and it just worked, albeit with a few glitches at first. Totally smoothed out by now, though. Sliders in Midi Conf. are still down to zero and grey, but hey, if it works, it works haha.

          • There we are – the bridge between the hi-fi industry and Apple. If we ever fail, the whole thing could crash.