So, they told that you need to spend quite large sums of money to get the state-of-the-art sound? It’s really good to know that there are audio components that don’t cost a lot, but sound great. Get yourself introduced to King Rex UD 384 / U-Power, a combination that allows a low-budget entry into the world of high-quality computer audio...
reviewer: Dalibor Kasac, August 2012 [www.digitalaudiofidelity.com]
model: King Rex UD-384 USB DAC/S-PDIF converter + U-POWER battery supply
manufacturer: King Rex Technology LTD, Taiwan [www.kingrex.com]
distributed in Croatia by: AUDIO SAN D.O.O. [www.audiodream.hr]
price: UD384 USB DAC - 410 EUR, U POWER supply - 170 EUR
readers' feedback: send all your comments by mail
review originally published at: this link
original text translated by: Marko Pecotic
These are two really small gadgets, and one is supposed to provide D/A conversion of digital samples even up to 384 kHz?!
Unlike many other audio components, this one is not fancy looking. Wires on the front, wires on the rear, a USB cable... All together, it looks more like a PC accessory than a fancy looking high-end audio gear.
Without pretending to send a message: "If I look this go - I must sound very good" - which is often so inaccurate, these two boxes from Far East are made to play music from a computer by a pure battery voltage.
UD 384 is a USB sound card (DAC) capable of converting all known digital frequencies from 44.1 to 384 kHz into analog signal, and it is also a USB-S/PDIF converter with a coaxial digital output. U-Power is a rechargeable battery with output voltages of 7.5 and 5V. All in all, this allows you to listen to any digital studio master on your PC with battery power supply. U-Power can continuously work between 10 to 12 hours, while battery charging takes some 6 to 8 hours.
I contacted Christina Wu, PR of King Rex. This lady is no doubt the best example of how the customer service of every audio manufacturer should look like - Christina was informed, friendly and genuinely interested to help! Specifically, I was wondering if UD 384 has a support in Linux operating system, and I also wanted to know what the company has done to prevent the passage of 5V voltage from the computer motherboard into the DAC. Both answers have delighted me! So, UD 384 has a native Linux support (no need for driver installation!). Secondly, U-Power has, besides output voltage of 7.5 V, a separate USB power output which provides 5V DC battery to power the USB receiver in the UD 384 DAC. This way, it’s possible (with the use of Y-USB cable) to avoid the nasty voltage of 5V from a PC motherboard, which normally enters the USB DAC's through conventional USB audio cables (regardless of price!).
King Rex already has a limited production of a new "Unanimous UART-USB Y" cable (expected price is approx 400 EUR), which has the so called "Y-USB" construction - one leg of the Y runs voltage for the USB receiver, the other leg runs the pure USB signal. DigitalAudioFidelity already has its own Y-USB cable, so everything fell into place perfectly for a review of this King Rex combo. Actually, this is, as I was informed by Christine Wu, the world's first review of this combo in Linux!
PART I. – USB DAC
Music comes first
What’s the purpose of reviewing audio gear? It is to try to objectively write about the sound. Not necessarily should everyone agree that one audio component is better that another. But, we should all agree about the definition of factors that make one component better than others. The only criteria that I have used during this review was: can this DAC sound like live music, like concert sound?
This review will reveal whether UD 384 can transform concert sound into a virtual soundstage in my listening room. This review will reveal how close can UD-384 come to live sound. I have done this review by listening to excellent recordings of chamber ensembles and various jazz trios.
UD 384 has no problem working in Linux Ubuntu Studio operating system, which was specifically designed for music, video and graphics applications. Unlike Windows, which is (unfortunately) so often used by many audiophiles, it has extremely low latency and therefore is almost ideal for audio playback. Christine Wu also said that UD 384 runs on Linux in their factory, and it, according to them, sounds much better than Windows OS.
Audacious player, which is an integral part of Ubuntu Studio, is not graphically as attractive as commercially-hyped JRiver Media Center for Windows. But in communion with the 3.2.14 kernel lowlatency it is able to surpass the audio playback of any application for audio playback in Windows.
More than once have I, on two computers, checked the differences in sound between Windows 7 and Ubuntu Studio. Ubuntu is significantly closer to live sound, while W7 is struggling with transients and timbral precision.
Another plus is the fact that UD 384 in Windows requires driver installation, while Linux runs as a plug'n play device, no drivers to install.
Three musical examples that can bury any audio component... or maybe not (?)
Over the years my choice of most difficult music samples, samples that are very difficult to be reproduced accurately, has narrowed down to a few musical tracks that are perfectly recorded, but their faithful reproduction is a mission-impossible even for very expensive Hi-Fi systems. I chose three digital musical examples that represent a great snack for any Hi-Fi system.
Schumann String Quartet op.41 performed by Ysaye Quartet is the first killer in my collection. The last track on this fantastic red book album is the last paragraph of the quartet no. 3 in A major. This dynamic, loud shot, fast and virtuosic piece can literally rip up your ears if your stereo system is not able to faithfully reproduce the sound of acoustic instruments. An array of strings crescendo and irritating fff violin passages is able to cause madness and listening irritation even on expensive systems.
Yes, I was skeptical how this small converter would sound in such cruel conditions. However, UD 384 sounded very, very good, it slammed the Schumann quartets. This small King Rex box is indeed capable of state-of-the-art conversion. Not a shred of aggression in fff passages, it has nice and euphonic timbre, and most of all - it gives me a good feeling that I am actually listening to the music, not its’ digital surrogate.
Encouraged by the initial success of this Taiwanese mini design, I was very interested to see how the music would sound on the second sample - Sigswald Kujiken Quartet performs Haydn's "Lobkowitz" Quartet op.77.
Original instruments of Kujiken quartet are able to cause a nervous breakdown due to their slightly nasally timbre. Sharpness of higher frequencies, characteristic for so many D/A converters, can in combination with the original sound of strings turn into a disaster. These instruments can, on a bad Hi-Fi system, make the impression that their resonant boxes are made of glass, not of wood.
It takes not more than just a few seconds to figure out how King Rex UD384 sounds...
My modified E MU 0404 USB, with seamless linear power (especially built for it), completely overcomes difficult and complex problem of conversion of digital images of the original instruments. Without any aggression, strings instruments get that typical brighter timbre of the original instruments. King Rex UD 384, but only in combination with U-Power supply (and connected by Y-USB cable), succeeded in this difficult task. UD 384 is a well-considered audio design, the creators of UD384 this converter know what live acoustic instruments sound like.
There definitely is a difference in the character of sound between UD384 and my modified E MU 0404 USB interface. It sounds like a difference between two different concert halls. Both converters allow a realistic musical reproduction, but E MU is more reminiscent of a large concert hall with lots of echo, and UD 384 sounds like a smaller concert hall in which the listener sits almost on the stage. It was quite pleasant to listen to the Haydn quartet - with the little help of my little friend from Taiwan.
Helge Lien Trio was my next choice. This is an ultra-popular album, the album title should mean something like "a state of pleasant nostalgic feeling". Now, that’s a real audio treat. The title track of this album, "Natsukashii" is an almost perfect classical jazz recording. And yes, Natsukashii is a true 24bit/192kHz digital studio master. This musical example will sound good in basically every Hi-Fi system. With one addition – in a properly set-up PC audio system with true conversion and power, this album will sound like you've added a sound booster and pumped various details which you weren’t aware of. None of that rich sound or echoes of the bass drum did UD384 take from Natsukashii. You can actually feel and hear the Helge Lien Trio instruments, the space between them and their close and intimate connection.
And yes, UD384 will allow you to fully enjoy Natsukashii - down to the very last detail.
Battery power – with or without it?
If you unplug the U-Power supply and plug the voltage converter plug that comes with UD384, Natsukashii will immediately sound much worse – piano will sound thin and short. Without U-Power, Natsukashii will lose the soundstage, the details, etc. Similar thing will happen with the battery power through the USB cable. If you replace 5V from U-Power with standard voltage from computer motherboard, the sound will become thinner and will lose loses its’ characteristic sparkle. That’s exactly what I expected - linear or battery power is an inseparable part if you’re after perfect D/A conversion. So, big, live and spacious sound is possible only if you are using UD 384 in combination with U-Power and Y-USB audio cable.
For quality musical background music from a desktop computer, you can also use a chopper (ie switcher) that comes along with UD384. But this is no longer the domain of this review...
384 kHz?!
It may seem unusual, but the fact that UD384 can go up to 384 kHz does not impress me at all. The choice of music recorded in 384 kHz is so narrow and uninteresting. The future will perhaps demonstrate us its’ the possible benefits. And King Rex is ready for the future!
In the end...
All in all - King Rex UD 384 is a top notch USB DAC that’s capable of sounding very close to concert-quality sound. Few details makes this small Taiwanese box stand alongside "big" D/A converters, (which will surpass UD 384 only by their price): huge virtual soundstage in which you can actually see and feel the musicians, plus a very defined and deep bass – these are the main advantage of this converter.
Audio market is full of audio components that are unable to meet even the basic requirements for faithful reproduction of music. King Rex is certainly not in such category. Its' price confirms that you don’t have to pay big bucks to get superb sound.
Are out there better DAC’s than UD384? Yes, sure! But, how better do they sound? And how much will you have to pay to get that difference? UD384 is a marvelous DAC that will, in combination with its’ battery supply, provide a really natural sound of acoustic instruments.
PART II: SPDIF CONVERTER
UD 384 has one chip (Rex King is not willing to say which chip it is) that does the D/A conversion. Digital-to-digital and digital-to-analog conversion take place simultaneously (that’s what the folks at King Rex say), so when one works, the other works too. Both conversions have native support in Linux with ALSA drivers and everything works flawlessly.
I checked the accuracy of the digital conversion with my Spectrum Analyzer. Of course, that's not the way that UD-384 owners will do it, so I want to emphasize that the lack of LED's showing the current frequency is a minus, perhaps LED's will be there on a possible MkII version of this DAC. Musical Fidelity V-Link 192, my absolute No.1 in D/D converters, has the best visualization of certain input frequencies. Almost like Christmas style, every frequency has its’ own LE-diode in different color.
In order to test the digital signal from King Rex, I needed another DAC that (via coaxial output) supports frequencies up to 192 kHz. I opted for Rega DAC that has nearly equal price to King Rex. Rega LED's indicate frequencies that enter into it, so I will be able to see what exactly is Rega's receiving form King Rex.
At the beginning, I must complain about clumsy british design. Why are 88.2 kHz and 96 kHz frequency marked with the same LED? Also, 176.4 frequency is not marked, and technical specifications say that Rega DAC supports it?! Why do Rega designers feel that they need a USB DAC that cannot accept anything above 48 kHz? Their way of thinking is quite opposite to designers of King Rex whose little DAC can swallow frequencies up to 384 kHz. So, Rega needs King Rex as a D/D converter that can handle all the digital studio masters. But, let's see if King Rex needs Rega?
Let’s see what happens with those striking musical examples from the first part of this test, examples that sounded so good with King Rex. Can almost ideal voltage conditions offered by UD 384 to convert USB to SPDIF signal allow Rega a perfect D/A conversion?
I went in a different order and I listened to Haydn's "Lobkowitz" Quartet via coaxial input in Rega. I immediately had to stop and repeat the beginning of the first paragraph. Then again. And again... Rega’s both paralel Wolfson 8742 DAC chips were not able to perform so well and euphonic as King Rex did with that one, unknown chip. Although high-frequency acuity was not a problem for Rega, liveliness and organic sound and atmosphere were sinificantly reduced. Rega sounds correct, but no way as interesting and luxorius as King Rex. If you've ever sat close to acoustic instruments during the concert, King Rex will very vividly recall that sound. Rega will not sound that good. Some reviewers will characterize Rega’s sound as very calm, but I'm quite sure that it is boring and significantly less persuasive than King Rex’s impeccable presentation of all parts of the audio spectrum.
And now, the real high-resolution audio na Rega – Helge Lien trio, Natsukashi!
Rega’s LEDs immediately turned to 192 Khz. Technically everything works perfectly. King Rex did a conversion into 192 kHz PCM and digital patterns have begun to enter Rega. Rega converts everything perfectly into an analog signal... But not as good as King Rex! Bass is less pronounced and somewhat lees defined, piano keys are just not that good. The life-like presentation is gone. Dimensions of soundstage are reduced. Everything sounds average and less interesting. So, King Rex is closer to live sound, while Rega sounds just like a good D/A converter.
King Rex does not need Rega to achieve the euphonic sound. King Rex alone can do it better than Rega, and I can only think of other converter that could give UD 384 its’ digital output.
Do not forget that Rega was tested under really good conditions: there was no polluted voltage (from the computer motherboard or from the mains) in the S/PDIF signal that was coming out of King Rex’s digital RCA output.
The test clearly shows that King Rex UD 384 works precisely as a D/A converter, but to evaluate its' S/PDIF sound quality – one should have significantly better audio component than Rega DAC. King Rex UD 384, with it’s U-Power and Y-USB cable, enters the crème-de-la-crème group of audio components. If you're not among audiophiles who think that audio components must be big and heavy, and you have realized that you can listen to digital originals only with a computer, UD 384 + U-Power will give you indescribable listening pleasure.
King Rex UD 384 needs around 200 working hours to fully burn-in. Once you’ve done that, you should know that its takes some 20 minutes to warm up before you seriously start to listen to some music. U-Power battery will give you more that 12 hours of continuous power, which is more than enough.
For those who want to know more...
I have a few albums that were ripped from SACD, directly from the DSD layer, with the help of Sony PlayStation 3. These are experimental files that I have (because I don’t not currently own a DSD converter) switched to 176.4 kHz or 88.2 kHz PCM signal, which is understandable to "normal" DAC's. Difference in sound between DSD and 192 kHz PCM could not be determined in a double-blind listening test, but some albums are so well recorded in the DSD technique that their ripped PCM replica gives a real pleasure for the ears.
After reading reports of professional studio technicians who advocate DSD recorders as devices that can pick up absolutely the most musical details during the recording, I realized that my experience with DSD files have good basics. Listening to SACD players, I never got the impression that I was listening to something really special. Some details sounded good, some average, some sounded awful. The answer to that might be the fact that the majority of these players have chips that convert DSD to PCM first, and then into an analog signal.
The situation has changed significantly after I transferred DSD files into HDD. Even when I transferred the files, for practical reasons, into PCM signal, DSD SACD layer still sounded very good: sweeter high range, organic presence of music and mainly fantastic bass.
I spent a few more days with King Rex listening to a few albums that have been transferred to the hard drive using the Sony PS3, directly from scarlet book format.
My favorite introduction to Bach's Well Tempered Piano, performed by Jacques Louisseier Trio, is one of DSD files transferred to 88.2 kHz PCM. Though there's just three acoustic instruments (piano, bass and drums), it is particularly striking how many musical details can be gain by a DSD recorder. The slow introduction to solo piano, which is gradually joined by bass and drums, in this perfect jazz adaptation of Bach's masterpieces... wow, it sounds so good!
Listening to really well recorded digital recorded music on this small King Rex, I was constantly chased by an idea of its direct comparisons with some of the multiple expensive converters. In a double blind test, it would be really interesting to A/B review this King Rex against D/A converters that cost 10x times more.
Conclusion
King Rex is an excellent, excellent product with a perfect balance between price and quality. USB DAC's generally work much better on Linux, but King Rex works wonderfully. My opinion of this King Rex is very high. Yes, it does not have LED's and that's a minus. I wouldn't mind using it a reference DAC in my system. I wouldn't throw away my tweaked E MU, but I couldn't decide which one is better.