KingRex UD384 DAC

KingRex UD384 DAC – 32 bit/ 384 kHz USB DAC

Kingrex U Power – battery power supply especially for UD384 and other USB gadgets

KingRex PSU MK2 7.5V – power supply specially designed for UD384

This is part one of the KingRex UD384 DAC review. The first part concentrates on introducing the UD384 features, build and usage. The second part will focus on the sound.

KingRex Technology ventured into PC HIFI, audio amplifier and DAC in the end of 2006. It has been producing very competitive, if not creative audiophile gears since then. Their goal is to continuously manufacture the highest quality products for the audiophile community (and at a reasonable price – added by me!).

The star of this review would be the KingRex UD384 DAC, a high resolution digital-to-digital and digital-to-analogue converter (DAC). It can be partnered with 3 kinds of power supply – wall adapter (comes with the package, optional KingRex U Power and optional KingRex PSU MK2 (7.5V version). The U Power is a battery powered supply and the KingRex PSU MK2 is a dedicated regulated power supply.

We shall focus more on the U Power and PSU MK2 though as that gets the best out of the UD384. UD384 definitely deserves a better partnering power supply to gain the sonic advantage.

KingRex UD384 Package

KingRex UD384 DAC package comes with the following parts:

  • UD384 converter
  • 7.5Vdc universal switching adapter with additional British wall plug adapter
  • USB memory-stick with user manual, high resolution playback demo, drivers and software
  • Rubber feet
  • USB cable
  • Warranty card

KingRex UD384 input

KingRex UD384 DAC is designed with minimalist concept. It accepts only a single USB input. All the money is spent on getting the best sound instead of providing the sometimes unnecessary options or features. The two functions that it does are:

  • Convert USB data to S/PDIF digital output to connect to external DAC.
  • Convert USB data to analogue output to connect to amplifier.

KingRex UD384 outputs

It has a pair of analogue RCA output to connect to amplifiers and an S/PDIF digital output (RCA) for users who chooses to use an external DAC.

Ease of use wise, I do find it a bit tricky to place the gears on a dedicated HIFI rack. Due to the small panel size, the input/output ports need to be at both the front and back panel. With the usual cabling connection being at the back, the KingRex UD384 DAC is rather unusual to have cabling on front and back.

Some weights are recommended too as sometimes the force exerted by the interconnects will tilt or lift the UD384. I find putting some wood blocks, crystals, sand bags and etc works pretty well and also acts as vibration absorber or diffusers that are beneficial to the sound. Try it!

KingRex UD384 front

As show in the picture, one side of the panels houses the output ports – S/PDIF coaxial and RCA analogue ports, the other side houses the input ports – USB and 7.5V power jack.

KingRex UD384 back

Some might ask, what are the difference between KingRex UC192 and KingRex UD384 DAC? KingRex UC192 is a digital-to-digital converter only. You’ve to supply your own DAC. KingRex UD384 DAC is a digital-to-digital converter AND a digital-to-analogue converter. The KingRex UD384 DAC is not a superset of UC192 though. UC192 has more digital output ports / formats than the UD384.

Let’s have a look here:

KingRex UC192 vs UD384

Which to get will really depends on your individual setup and planned applications. The highlights above give you a good idea on their main differences and will enable you to decide on which to get. 32bit 192kHz-484kHz music titles are not very common yet but this does enable it to be future-proof when the time comes.

Do take note that the UD384 and UC192 RCA S/PDIF output supports up to 192kHz sampling rate only. For 384kHz support, user needs to use the internal DAC of the UD384, or use the I2S output of the UC192 (after upgrading the firmware).

KingRex UD384 memory stick

This is the USB stick that comes with the unit for software / firmware installation. I definitely prefer this to the CD/DVD disc that comes with other products due to size and longevity concerns. To avoid loss of the USB stick, I would recommend users to stick it at the bottom of the unit as safe keep. Storing it at the shipping box is OK too if you are sure that it will never get lost eventually. If it is lost, worry not as the drivers and software are available online at KingRex website.

The manual contains very detail instructions of installing the driver and setting up the UD384 for playback. Buyers do not have to worry about installing the UD384 into the computer playback system. It is hard to go wrong with it even for beginners.

Since Windows 8 will be in the market at around 2012, I asked Christine about the Win8 support for UD384. She replied that KingRex will arrange the full Win8 test in third quarter of 2012 and it should be supported then. So no worries for new users or existing users that would like to upgrade their PC.

KingRex UD384 feet

Rubber feet are provided to for both the KingRex UD384 DAC and U Power units. Users can play around with soft and hard support to tweak the sound as per user preference.

KingRex UD384 board

The UD384 can be divided into 5 main quadrants.

  • Q1, top left – power input and supply filtering
  • Q2, top right – analog output filter
  • Q3, center of PCB – transceiver + DAC integrated circuit (chip)
  • Q4, bottom left – USB receiving
  • Q5, bottom right – S/PDIF digital output

KingRex UD384 Pulse Transformer

If user uses the KingRex UD384 DAC as a USB to S/PDIF converter, the Pulse PE65612NL pulse transformer couples the digital output to the external DAC, which is a superior solution compared to those without a pulse transformer. It isolates (galvanic isolation) the transmitter from the receiver and reduces common mode noise, EMI and eliminates potential ground loop as well. The Pulse PE65612NL is designed for use in interconnecting digital audio data transmission systems and complies with the AES 3-199X or IEC 958 regulation.

KingRex UD384 DAC chip

The label of the DAC chip has been erased though. I could not get any specifications out of the manufacturer datasheet. It looks like a customized single chip solution with USB transceiver and DAC integrated. I wonder which manufacturer that is, and what kind of technologies are used in this integrated transceiver / DAC chip. I guess one of the appealing properties of UD384 is about not knowing what it is made of!

Sometimes we’re far too obsessed with specifications and figures that blind us completely. A DAC is not just about the DAC chip used, it is about everything, from the chassis to the power supply and etc. Also, take tube amplifiers for example – they’ve high distortion figures but the sounded wonderful. Anyhow, the proof is in the pudding. What’s important to the sound is the design implementation. A DAC with excellent DAC chip but lousy PSU, output filter or layout is just not going to sound very good.

KingRex UD384 TCXO

The KingRex UD384 DAC uses a customized low jitter TCXO for better performance. 1PPM means 1 defect part is acceptable within a 1M units sample size. I wonder if that is the frequency accuracy / tolerance specifications of the TCXO. If it is, then it is an excellent TCXO! Even for those TCXO that we use on computer motherboard that operate in MHz and GHZ ranges, we’re using 5 to 30PPM parts only! All the incoming data is re-clocked with this TCXO.

KingRex UD384 PSU

There is no digital audio interface receiver device seen in the KingRex UD384 DAC. Could this mean that the DAC chip could handle it all? Then it is not just a DAC chip, but a SOC – system on chip! Without any identification, we can only guess.

High quality Nichicon capacitors are used at the power supply section. The DC input jack is protected against polarity inversion too with a diode in series.

KingRex U Power

After looking at the UD384, let’s switch focus to the U Power and the PSU MK2. Is off the mains the best power supply you can give to audio equipment? We shall see in this review – battery power supply versus well regulated dedicated PSU.

KingRex U Power back

After looking at the UD384, let’s switch our focus to U Power. The U Power comes with two output ports – 2.5mm DC jack with 7.5Vdc output and a USB port with 5Vdc output. The 7.5Vdc comes direct from the battery. The USB 5Vdc is a regulated output from a linear regulator. The capacity of the U Power is 2600mA per hour. The KingRex U Power can supply to both KingRex UD384 DAC or other USB powered device as well.

KingRex U Power power input

On the input side, it only accepts 2.5mm DC jack for charging the batteries. Charging uses the Meanwell SMPS wall adapter supplied in the package.

KingRex U Power output

Both the KingRex UD384 DAC and KingRex U Power are housed in rigid 3 piece extruded aluminum (body, front and back panels) case. The only difference between the two are the front and back panels to cater for different I/O ports.

KingRex frame

The PCB slides smoothly into the cavity in the middle of the chassis. The PCB fits perfectly on the middle track and the front / back panel. Due to the small unit size and thick wall, the chassis itself is very solid and chances of vibrating or ringing is very low.

KingRex U Power frame

KingRex U Power PCB

On the top section of the KingRex U Power PCB, houses a dual Sanyo Li-ion 3.7V batteries connected in series to make 7.4V out of the unit. Li-ion is one of the most popular types of rechargeable batteries since it has the best energy densities and NO memory effects like the NiCd batteries. What’s memory effect? It is the situation in which certain batteries gradually lose their maximum energy capacity if they are repeatedly recharged after being only partially discharged. The battery appears to memorize the smaller capacity.

The UD384 and U Power combo could work for around 12 hours. To get a full charge on the U Power, it needs about 7 hours. The U Power is guaranteed for 500 times charge & discharge.

KingRex U Power regulator

p>Charging is not just done via the wall adapter alone. The input power is post-regulated by the ST L200C Adjustable Voltage and Current Regulator.

One can listen to the unit while the batteries are being charged. The CHG/DC Out switch disconnects the wall adapter for off the mains listening or when the batteries are fully charged. With the ST L200C regulator being used, it should not have big impact on the results when listening while charging the battery.

For serious listening, it is recommended to switch to DC Out and remove the wall adapter totally to completely isolate the unit from the mains.

KingRex U Power Indicator

KingRex U Power Outputs

The U Power has nice features of low battery detection and LED blinking. It is achieved by the HA17555 timer and the PC817 photocoupler circuit.

KingRex U Power 5V

This is the LT7805 fixed regulator used for regulating the 7.5Vdc battery output to 5Vdc for the USB port.

KingRex UD384 & PSU

KingRex PSU MK2

KingRex PSU MK2 is the improved version of the already pretty good PSU. It looks almost the same as the original version except that it us using 6N Furukawa PCOCC wiring throughout and the DC jack is using a 3-pin XLR Neutric connector. This provides a better interconnection between the PSU and the DAC. The PSU review has been posted before, check out the below link:

KingRex T20U + PSU review. .

For more details on the PSU design, please refer to the KingRex T20U review. On the other hand, I’ve tried the KingRex PSU with other DACs (Diyparadise Monica and Super Pro DAC707) and it brought me delights by improving the sound substantially.

KingRex PSU MK2 output

Here are some tips from KingRex:

  • Charge the U Power when it is first used as it should be in low power stage for shipping.
  • Make sure your computer is USB2.0 compliant.
  • The UD384 should be with the latest firmware, do not upgrade it unless necessary.
  • CPU must be dual-core or above.
  • Suggested OS: Win XP/Vista/7 or Mac OS 10.5 to 10.7.
  • Suggested Win software: Foobar 2000 + SIO4All (XP) or + WASAPI (Vista/7)
  • Suggested Mac software: iTune + Pure Music, Amarra might be OK too.
  • There are sample demos in the USB memory stick. Check it out!
  • DSD format can be supported by converting it to PCM first using Foobar 2000 + DSD converter or with the Pure Music automatic conversion.

That concludes part 1 of the KingRex UD384 DAC review. Part 2 will be posted soon. Stay tuned!

Price – U$479 for UD384, U$189 for U Power, U$350 for PSU MK2


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