Review: Kingrex UD-384 and U-Power

We came across Kingrex's product while searching for a power supply upgrade for another manufacturer's DAC.  Kingrex's PSU MKII proved to be one of the most cost effective upgrade we can recommend to a USB or wall wart powered DACs.  We weren't the only one, but also numerous favorable feedback from various internet forums.

At the time Kingrex also makes a very nifty USB to SPDIF converter (they prefer to call it DDCs - digital to digital converters) called the UC192 (still in the line up, firmware upgraded to 32/384 conversion through i2s).  We were so impressed with the power supply that we contacted Kingrex for a review unit.  Kingrex informed us that they were about to launch a new model, which is not only a DDC, but also a high resolution 32/384 capable DAC/DDC plus a dedicated power battery supply designed for it.  So we decided to wait for the UD-384 and U-Power which are the subjects of our review here.

Dynamic Duo


The combo arrived and we are quite surprised to see how small they are.  They are light (less than 200g each) and compact, each about eleven cm long, and made of anodized extruded aluminum.  They are quite well made but rather light and 'casual' looking.  The U-Power is optional ($179) and in such case the UD384 would be powered by a supplied generic 7.5v wall wart.  You can then choose from two upgrade path - the U-Power, or the more expensive AC-powered PSU MkII, please do note that you will have to specified a 7.5v version for the latter.  For those of you who are suspicious of  how good clean power can do to the sound, you'll be surprised that for hifi equipment, a significant percentage of the overall sound quality depends on that.  Basically you are what you eat.

The unique thing about the UD-384 (US$479) is that it is both a DAC and a USB to SPDIF converter.  We think this is such a nifty idea since you may, in the future, want to upgrade to a more extravagant DAC which you can still use the unit's asynchronous USB conversion that works up to 24bit/192kHz (SPDIF's technical limitations prevents the UD-384 to output higher than 192kHz).  There are however no other digital inputs except USB.  Drivers are supplied for Windows, there are no drivers necessary for Mac users.

Internal digital engineering is quite unorthodox.  For instance, there is a single 'anonymous' chip handling USB receiving, and digital to analog conversion.  There is also a single high precision thermally stabilized TCXO 1ppm super low jitter clock giving beat to all of the sampling rates covering 44kHz to 384kHz.  High quality resistors and capacitors are used through out with nice attention to details on where these components would have effects on the sound.  The other peculiar thing about the UD-384 is that when used in DAC mode, with the current firmware, it can decode the highest specified 384kHz but not 352.8khz.  We believe this is due to its minimalist sigle-chip/single-clock configurations.  However, Kingrex's engineer probably has reasons to go minimalistic as proven by its sound quality - read on. 


The U-Power internals are also well thought-out.  There are  two 3.7v Li-ion batteries supplying 2600mAh of power. Charging is done through the supplied wall wart, and a circuit disconnects noisy A/C supply during battery playback. There's also a USB power port on the U-Power, I was hoping this is a power input but it actually is an output which can feed 5v power to a USB device.

They rock!

How does it sound? In one word - impressive.  If you do a blind test having your typical big shiny aluminum box high end DAC side by side and ask your friends to guess, they would surely have it wrong.  What we are most surprised by is its ability to handle slam and weight.  The resolution is also amazing with air and openness rivaling the best out there, both with normal 44.1k CD rips and native high resolution files.  Having said that, this is not a DAC for detail freaks.  It doesn't draw you into the minute details like some of the DACs do, but more the coherent message.  It just excels on tempo and energy and plainly "boogie".  Soundstage is spacious, precise and wide, with images being so stable you can reach out and touch them.  Although the stage is not as deep as some, but enough for you to work out the layers without feeling a wee bit of congestion.  This is not a hifi-sounding DAC, it is ever so smooth without edginess of lesser DACs.  Pace Rhythm and Timing are excellent breathing down the neck of much more expensive units.  The mid bass is tight but never bloated, which puts it on the clean and taught side of the scale as opposed to romantic and lush tendencies of  tube peers.

Most of our listening was with the supplied U-Power unit.  However, we did have on hand the dearer Kingrex PSU MkII for comparisons.  The differences were quite small.  You will have a slight better macro dynamic with music with big dynamic range swings, but the all else were excellent as it is.  The synergies of the two units are there and is highly recommended you get the UD-384 and U-Power as a combo.

Conclusion

Once in a while you come across a product that are so deceptive simple in appearances. These little boxes proved to be so much for the price.  If you are new to computer audio and do not want to spend a fortune on state-of-the-art converter or DAC, the UD-384 is a great future-proof USB/SPDIF converter with a superb DAC to boot.  We think the UD combo is the best sounding DAC we have heard so far in its price range.

Review : Kingrex PSU Mk2

They say garbage in, garbage out.  Think about it, the sound you are hearing from your audio system, is actually energy from power plant, sub station, power transformer, home junction box, power outlet, and then your equipment.  Taking cues from recordings and convert electricity to sound waves.  


It's been said that sonic contribution of a typical DAC would be 30% DAC chip, 30% analog output stage, 30% power supply, and 10% for the other parts combined.  Your typical consumer piece of equipment often comes with cheap wall-warts or switching power supply which in itself is notorious for noise - which is measurable and often heard.  Psycho-acoustically we perceive this as "grunge" and "edginess" rather than higher noise floor. 


Soon after our review of the Calyx DAC 24/192, kind readers were suggesting that the DAC may be better treated with an outboard power supply.  During our original review, the Calyx was powered primarily by USB.  It uses an energy storage and regeneration circuit, internally generates 12v voltage rail and outputs 6.5v over its balanced XLR outputs from USB's mere 5v.  The included wall wart was tested and found indifferent in terms of sound quality.  We were equally curious whether we can still improve it excellent sound quality so we contacted Kingrex for a review of their latest Power Supply Unit, which is in its Mark II incarnation.

Kingrex PSU MK2 power supply unit is available in 3 models with output voltage 12V, 9V, 5V.  The units are priced at just below US$350 each.

The 5V version would power the Calyx DAC 24/192, Squeezebox Touch, Onkyo ND-S1 iPod Transport, etc.  The 9V version would power a Wadia 170i/171i Transport, Squeezebox Classic/Duet, M2Tech EVO.  12V version also available.

Inside the PSU Mk2 there's a 48VA toroidal transformer, a regulated power-stabilizing circuit with 8 capacitors, 5 x 2200μF at AC input stage and 3 x 4700uF at DC output stage. 6N Furukawa PCOCC wiring through out.  The unit has a 3 pin Neutrik DC connection on the PSU side to DC jack (electronic side). The included DC jack is a 5mm external, 2mm internal type, which is actually too short for Calyx's input.  We had to modify it by cutting the original jack out and replace with a longer one.  If you plan to use the PSU with the Calyx, please request a longer DC jack from Kingrex.

The Calyx has a selector in the back that switches between USB power and 5v DC, so it is easy to compare the effect of two power sources with out having to match levels or  interconnects etc.   There was a soft "click" when changing the power source and that's about it.  During this test we used Wireworld Platinum Starlight USB cable whose unique feature is the isolation of power leads from data conductors. 

Results? First was Bill Evan Trio's Waltz for Debby in 24/192kHz format.  To get the cymbals in this recording right is one of the test we constantly use to fish out digititis so common in lesser equipment.  Cymbals should bite, but at the same time never harsh.  There should be air with nice natural decay. Both USB power and PSU performed equally well.  We also couldn't hear much difference on the piano nor the softish acoustic bass.  We were quite impressed how clean the Calyx's USB power regulation is.  Next up were Herbie Hancock's Imagine Project and Manu Katche's Third Round - both excellent modern-day jazz recordings with serious bass and drums.  Now the Kingrex/Calyx combo proved to be something the Calyx alone always wanted to be!

Deep bass now has fundamental we never thought missing.  Subjectively, we felt that the low end extension extended down another octave or so.  It is also ironic when you have more infrasonic reach, you feel you have more "air" as well, even though the upper frequency range is more or less the same.  With air, you have a better sense of where the images are in the sound field.  Room ambiance are now better portrayed.  The soundstage becomes more three dimensional.  Slam and weight were also noticeably better with more visceral impact without muddying the mid-bass.  Calyx was a little short on pace and rhythm last we tested it, but now with the Kingrex PSU Mk2, the DAC can now really boogie.  The combo closes the gap with our reference Weiss DAC 202...much closer than before.

We also have on hand a Squeezebox Touch, which we upgraded with a Teddy Pardo Power Supply and found it to be a notch better than stock wall wart.  We did tried the Kingrex on the Touch and thought it offered the same level of performance as Teddy's (tighter bass and extended highs than stock).  Just a caveat that the magnitude of improvements are not as significant as the Calyx's but worth the upgrade if you opt for best possible sound from the Touch.

Highly recommended.

CI Audio VDC•9.0 and VDC•SB power supply upgrades

Channel Islands Audio's VDC•9.0 (US$279) is the perfect upgrade for Slim Devices/Logitech Squeezebox Duet, and the Wadia 170i/171i Transport. When used with either device, the upgrade eliminates noise caused by the standard switching supply, which can contaminate the internal digital and analog circuits.

The design utilizes a low noise/high current transformer, with discrete Schottky diode bridge rectifier, AC line filter, precision voltage regulator circuit, and 13,600uF of filter capacitance. Available in 120 or 240v input. Cables for Logitech Squeezebox Duet and Wadia 170 iTransport included.

Another version, the VDC•SB (US$259) is the 5v upgrade for Logitech Squeezebox Touch and the Classic SB3.