"If it measures good and sounds bad, it is bad.
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Review: Kingrex UD384 USB DAC (32bit/384Khz) & UPower

Posted by Amine Slimani on February 4, 2012 at 1:55 PM

Do we really need 32bits/384kHz capability in a DAC? That is the first question I asked myself when Christine from Kingrex asked me if I were interested in reviewing their newly released UD384 usb dac. It is until recently that 24/96 and 24/192 have become more common but there is still a long way to catch up with the choice of material released in the 16/44 RBCD format. So why bother releasing such a DAC? After listening for several weeks to the Kingrex UD384, I think that there is at least two possible explanations. First, there are record companies, such as 2L, that are starting to offer higher resolution files than 24/192 (for instance the 24/352 DXD format, or even the non PCM 1bit DSD format). Second, having a 32/384 capable usb DAC allows you to upsample any file (from mp3 to DSD) into 384 KHz directly in your media player. Whether that is a good or bad thing will be discussed later.


However, besides the 32/384 capability, the UD384 distinguishes itself for most DACs by its optional battery power supply. The UD384 can indeed either be sold with a regular (read non-audiophile) 7.5v SMPS power supply or it can be upgraded with a battery power supply. My review unit came with the optional U Power battery supply. Having previously directly compared a usb powered Hiface with a battery powered Hiface, I was staggered by the kind of improvement an upgraded power supply could provide to a source.


While I have been pretty happy with my dac19dsp, which is limited to 24/96, the 32/384 capability and the battery power supply on the UD384 piqued my interest. The UD384 takes on a rather different route than my reference dac: while the dac19dsp uses old R2R PCM1704uk chips, discrete output stages and is 24/96 limited, the UD384 seems to be using an integrated usb/dac chip and non-discrete (IC) output stages. For the power supply, the dac19dsp is using a big R-Core transformer followed by some decent filtration, while the UD384 goes with the smarter route of battery power supply.


So how does the UD384 sounds like? Read on to find out.


Description of the UD384 and the UPower


The Kingrex UD384 is an async USB DAC and Digital to Digital (USB to Spdif) converter capable of up to 24/384 sample rates (from its USB input).

The Kingrex UD384 can be operated either from a regular 7.5v SMPS or from the UPower, which is the optional battery power supply.


Below are some specs on the UD384 and UPower:




UD384 (32bits/384Khz USB DAC )

Input: USB x 1

Analog output: RCA x 2 (Rx1 Lx1)

Digital output :SPDIF x 1       

Sampling rate support :44.1Khz, 48Khz, 88.2Khz, 96Khz, 176.4Khz, 192Khz, & 384Khz(384Khz for USB DAC only)

Supported bit rate: 16 / 24 /32bit

USB:2.0 high speed

Adaptive Clock Generator for Audio Streaming Synchronization

Asynchronous mode changeable through DFU Tool

Power requirement: 7.5V/250mA

Size: 110x82x24mm

Suggested MSRP : $479/pc



U Power:


Pure DC output battery power supply unit

      I.       Two output :

A.    2.5mm DC jacket: 7.5V DC output

B.     USB A :5V DC output(through linear regulator)

II.       Major component: High quality Sanyo Li-ion battery.

III.  Power volume: 2600mA/hr. Included special design for isolated protect circuitry for two Li-ion batteries.

IV.  Using fully high quality aluminum for styling & cooling.

V.    Low battery indicator design for charging reminding.

VI.  CHG/DC OUT switch. Fully isolated the charging and discharging. It will free the AC noise from the charger.

VII.   Parallel charging- each battery cell could charge to its maximum by the design.

Suggested MSRP: US$189/pc


Review System


Equipment used for the review


Computer source: HP Pavillon DV6 (Core i7, 8GB), Windows 7 64bits SP1, Fidelizer, JRiver Media 17

Transports: Audiophilleo 2, Kingrex UD384, Jkeny’s modified Hiface MK1, Audio-gd Digital Interface (w/ Tentlabs upgrade clock), Teralink X2, Musiland Monitor 01 USD, EMU 0404 USB

DACs: Audio-gd DAC-19 DSP (with DSP1 V5), Kingrex UD384

Amplifiers: Audio-gd C2, Little Dot MKIII

Headphones: ALO recabled Beyerdynamic T1, Sennheiser HD650 with Artisan Silver Dream upgrade cable

Digital interconnects: Hifi Cables Sobek BNC, OyaideDB-510 BNC, Wireworld Ultraviolet USB

Analog Interconnects: Artisan Ultimate Silver Dream RCA, Norse Audio custom 8 conductor UP-OCC ACSS, Deep Sounds SPS ACSS, Kimber PBJ RCA

Power filtration: Bada LB-5600 Filter, Essential Audio Tools Noise Eater, Essential Audio Tools Pulse Protector, Supra Mains distributor

Power cords: Hifi Cables & Cie PowertransPlus (x2), Hifi Cable & Cie SimpleTrans, Olflex power cords

Vibration Control: Aktyna ARIS decoupling feet, Maple and Acrylic Platforms, E&T rack, Stabren Damping pads, Sandbox, Brass cones, Vibrapod, Yamamoto Ebony footers and Various Herbie’s Audio Labs tweaks

Reference tracks used for the review


My (usual) reference tracks:


CD Quality

Mahler - Symphony n 5- Decca - 16/44

Sol Gabetta - Schostakowitsch Cellokonzert Nr. 2/Cello - 16/44

Vivaldi - Concertofor 2 violins - Carmignola/Mullova - 16/44

Natalie Dessay - Italian Opera Arias - Emi Classics -16/44

Puccini - La Boheme - Decca - 16/44

Glenn Gould - The Goldberg Variations (1981) - 16/44

The Essential James Bond - City of Prague Philharmonic orchestra - 16/44

The Dave Brubeck Quartet - Take Five - HDCD - 16/44

Diana Krall - Live in Paris - 16/44

Norah Jones - Come Away With Me - 16/44

Patricia Barber -Companion - 16/44

Johnny Cash - TheEssential - 16/44

Soundrama - "ThePulse" Test CD - 16/44

High Resolution quality:

Rachmaninoff Dances -HD Tracks - 24/96

Mozart Violin Concertos - Marianne Thorsen - 2L - 24/96

Dunedin Consort -Messiah - Linn Records - 24/88

Glenn Gould – The Goldberg Variations (1955) – HDTracks - 24/96

Keith Jarrett - Paris/ London - Testament - 24/96

Jazz at the Pawnshop- HD Tracks - 24/88

Alison Krauss and Union Station - Paper Airplane - 24/96

Ella Fitzgerald /Louis Armstrong - Ella & Louis - 24/96

Diana Krall – From this Moment on - 24/88

Diana Krall - TheGirl in the Other Room - 24/96

The World's Greatest Audiophile Vocal Recordings - Chesky - 24/96

The Kinks - One forthe Road Live - 24/96

The Eagles - Hotel California - HD Tracks - 24/96

Head-fi/Chesky Sampler - Open Your Ears - 24/96


Other reference tracks


I personally think that the best way to evaluate any audio equipment is to use music that one is already familiar with; however, given that the Kingrex is 32/384 capable I downloaded all the files that were available at 2L in order to compare the same music at different sample rates (44.1, 96, 192, DSD, DXD). So a great thanks to 2L recordings for offering for free such high quality samples.






The UD384 is fairly easy to set-up (by audiophile standards). You only need to worry about connecting it to the computer via a usb cable and to your amplifier via rca interconnect cables. In comparison with the Audio-gd solution (Digital Interface + dac19dsp) you save 2 power cords, a digital cable and a lot of space.


However, while it easy to set-up, I find that it is perhaps too small and somewhat cumbersome. I wish that Kingrex released a single unit version with a built-in battery power supply which would avoid having a few cables dangling around between the battery power supply, the UD384 unit and the smps power supply. That is however just nit-picking as the UD384 involves little extra cost to set-up properly contrary to many DACs I have tried so far.


U Power


If you are considering the UD384, you ought to think of the “optional” U-Power as a mandatory piece of equipment. Without the U-Power, the sound can be a little bit congested, bright and lacking naturalness and definition. Given the low price (less than $200) of the U Power and its effect on the sound, it shouldn’t be optional in my opinion.


USB cable


Weirdly enough, the UD384 was more sensitive to the quality of the USB cable than the Audiophilleo 2. Given that the AP2 is usb powered and that the UD384 is externally powered, I was expecting the USB to have little to no effect on the sound UD384. I suspect that somehow the UD384 is not 100% galvanically isolated from the usb power line of the computer.

However, you need not to ruin yourself as the relatively affordable Wireworld Ultraviolet usb cable was more or less as competent as the far pricier Artisan Pure Silver usb cable.


Vibration control


Given the low weight and small size of the UD384, it didn’t seem to be affected much by vibration treatment (contrary to the dac19dsp). For the review, the only “tweak” I used was a Herbie’s Audio Stabilizer on top of the unit, and it was more to add weight than to change the sound. Given the lightness of the UD384, it can be easily moved around by the USB and RCA cables.



The UD384 as a USB to Spdif converter


While I did most of my listening of the UD384 as USB DAC, I also tried the unit as USB to SPDIF converter. I will not go to much detail about the sound but here is what I found out: the UD384 is a very good usb to spdif converter, better than the audio-gd Digital Interface for instance, but not as good as the Audiophilleo 2. If your goal is to use the UD384 solely as a usb to spdif converter, there are better alternatives. The UD384 throws a pretty big soundstage as an spdif converter but lacks the details and low level resolution of the AP2.


So the Spdif out is a nice feature but a prospective buyer should not choose the UD384 for sole spdif transfer. It is probable that something like the Stello U3 or JK MK3 will give similar or better performance for a lower price point. However, the real strength of the UD384 is when it is used as a USB DAC. From hereafter my review will describe the sound of the UD384 as a USB DAC unless stated otherwise.


As a side note, I should perhaps mention that although the UD384 did not equal the performance of the AP2 as USB transport, I was pretty surprised to have the UD384 throw a wider and deeper soundstage (in size) than the AP2. That led to investigate possible “enhancements” to the AP2 which led me to ordering the Aqvox USB power supply. Hopefully, the Aqvox will improve the soundstage size while retaining the other qualities of the AP2 (more on that in a future review).



Sample rates – How high should you go?


Before trying the UD384, I used to believe that anything above 96K was pretty much useless for a DAC. In fact, one of the best DACs I have listened to was limited to 20/48.

It has been well documented that is rather difficult to construct digital filters at 16/44 that will preserve the time domain performance in our hearing range (20 Hz-20 KHz for those who have excellent hearing). While in theory 16/44 is sufficient to cover up to 22 KHz, it involves using complex filters that can have a good behavior in the frequency domain but a poor one on the time domain (impulse response), or vice versa. And even with the use of very sophisticated and heavy calculations, there is always a trade-off to be made between the frequency and time domain performance. Moving the sampling to 24/96 makes it far easier to construct digital filters that are good on all parameters. Some audio experts, such as Dan Lavry, say there is no need to go beyond 24/96. Other people insist that 24/192+ and DSD are necessary to maintain a perfect impulse response, at least one that sounds close to the real thing.


Since there is no real consensus on the theory side, I started listening to the UD384 at different sample rate with an “open” mind. What I realized after listening to the same files at different sample rates on the UD384 is that the Kingrex unit benefits greatly from higher resolution files. Christine from Kingrex insisted on trying DSD files and after listening to them (using JRiver upsampling to 24/384) I can confirm that I found them to be excellent, albeit not superior to 24/192 and 24/352 files.

From my experiments, I found the sweet spot to be on 24/192 files: the Kingrex really starts to sound natural at 24/192 sample rates and higher. So given that most music libraries are composed mainly of 16/44 files and perhaps a few 24/88 and 24/96 files, is there a real benefit in having a DAC that can perform so well at 24/384? The answer is yes if you use a superior upsampling such as the one provided in J River Media Center. Upsampling from 16/44 to 24/384 on J River gives a big improvement in sound. The resulting files are not as good as the native high resolution ones but there is a definite improvement with a good upsampler (SoX on Foobar does not give as good results subjectively for instance as those of JRiver).


Side note: For whatever reason, the UD384 does not seem to support 24/352 files (but supports 24/88 and 24/176). Given that I upsampled everything to 24/384 it was not a real problem, but I thought it was worth mentioning.

The Sound


Timber and Tonal Balance


When I first listened to the UD384 (with little burn-in and 16/44 files) I was a little bit disappointed with the sound. But, as I mentioned in the previous section, after trying high resolution files (24/96 and higher) and upsampling, I felt that the UD384 was definitely better balanced at those higher sample rates; Indeed, the UD384 seems to belong to the class of DACs that can benefit greatly from higher sampling rates. As a counterexample, my reference DAC, which is limited to 96K, has rather the same tonal balance regardless of the sample rate. Given how much of a difference JRiver and upsampling to 384K made to the sound, you should keep in mind that all my comments below are based on that particular set-up. Using Foobar with no upsampling does not give nearly as good results as mentioned here.


The UD384 has an overall well balanced sound. Contrary to many sub $1000 DACs, it doesn’t have a mid-treble brightness to simulate fake resolution or a mid-bass bump to simulate fake warmth. The UD384 is rather coherent from top to bottom with no emphasis on any part of the frequency spectrum. The only deviation I could detect from the “absolute sound” is a small lack of extension at the frequency extremes, especially in the low frequencies. To be more specific, the UD384 does not hit as hard on the bass as the Audiophilleo 2 and DAC19DSP (V5) combination does for instance. Other than that (small) subtractive deviation from the absolute best I have listened to in my personal system, there is not much to criticize about the tonal balance of the UD384.


As for the timber of the UD384, I was pleasantly surprised with its behavior. Up until I tried the UD384, I was rather convinced that it was almost impossible for a sub $2000 sigma delta DAC to render pianos and violins as convincingly as old fashioned R2R DAC seem to do so well.

[Note that I do not know for certain that the UD384 uses a sigma delta design but given that it seems to be using a custom integrated USB DAC chip, it is highly probable that it is a sigma delta design. To the best of my knowledge the PCM1704 is the last R2R audio dac chip still being manufactured.]


Playing The Goldberg variations by Glenn Gould (I have the 1981 performance in 16/44 and the 1955 version in 24/96) was a truly special experience. The sequence of the sound emanating from the piano is fully preserved: you do not only distinctly hear the hammer hit the strings but you also clearly hear the strings and the soundboard resonate afterwards. Some DACs put more emphasis on one part or the other but the UD384 seems to get everything right. But is it perfect? It is very close to the sound of the AP2 and dac19dsp combination, although neither as rich nor as diversified sounding. But overall, there is very little to criticize about the UD384, especially considering its price; indeed, as mentioned earlier in the tonal balance section, the UD384 sins are of omission rather than commission.


On less technically difficult recordings such as Diana Krall Live in Paris (16/44) or the Girl in the Other Room (24/96) the voice of the singer and the accompanying instruments (including the piano) sound wonderful and there are chances that you will hear new details and subtleties with the UD384, regardless of where you are coming from.


Comparing the sound produced by the UD384 against that of the AP2 and Dac19dsp combination is very interesting. While the dac19dsp is dense, “grounded” and slightly dark, the UD384 is airier, livelier and more sophisticated on the top end. The center of gravity of the dac19dsp seems slightly left of perfect (left being the low frequencies), while the center of gravity of the UD384 seems a little bit right of an ideal perfect. However, those are slight deviations from absolute neutrality and there is far more coloration among different recordings than there is between these two DACs.


However, it should be noted that these qualities about the UD384 are only apparent when one is using a good media player (such as JRiver 17), high resolution files or upsampling, a good usb cable and most importantly the outboard battery power supply.

With those pre-requisites, the UD 384 can paint a very interesting and harmonically rich picture.


Speaking of harmonic richness, I should perhaps talk about the perceived “contrast ratio”. While the UD384 sounds “sophisticated” and airy in the top end, it doesn’t have quite the same contrast ratio as that of the AP2 and dac19dsp combination which seems to be able to paint with slightly greater precision the difference in timbers of instruments and voices.

Keep in mind that the AP2 alone costs around the price of the UD384 and its battery power supply.


Unlike many mid-tier converters (and most sigma delta converters), the UD384 does not have a choppy representation of timber of voices and instruments. The UD384 rendition of sounds is a very smooth one, albeit not as sharp and defined as that of the AP2 and the dac19dsp combination.


One might think that the smoothness is an indisputable weakness; however, given how many poor recordings there are, it is sometimes a relief to have an excellent DAC such as the UD384 that is a little bit forgiving on the top end.  

Soundstage and Imaging


From the beginning, I was very impressed with the Soundstage and Imaging of the Kingrex UD384, and I also believe that it might be one of the biggest strengths of the unit.


It was rather apparent from the start that the UD384 was capable of throwing a huge, well layered and hyper defined soundstage. This was especially noticeable when using the angled driver ALO Beyer T1.

As good as my reference set-up, namely the Audiophilleo 2 paired with the Audio-gd DAC19DSP, is in other areas, the UD384 is capable of reproducing a bigger and deeper soundstage. The Audiophilleo/Audio-gd dac19 combination can still have a more holographic soundstage on some tracks, but the ability of the UD384 to draw a very deep and layered soundstage is pretty impressive.

Removing the ultra-low jitter Audiophilleo source from the equation and comparing the Kingrex UD384 against the DAC19DSP (with the Audio-gd DI as a source for instance) gives a far clearer win in this department to the battery powered Kingrex UD384.


I should perhaps mention that I mainly used the UD384 with the excellent Artisan Ultimate Silver Dream interconnects. Trying out different (and lesser) cables causes the excellent soundstage to collapse to different degrees. So in order to “squeeze” that kind of performance from the UD384, the use of high quality RCA interconnects seems to be necessary.


Furthermore, while the sound-staging can be huge at times, it does not come at the expense of the imaging. For instance, when I connect my dac19dsp to my c2 amp through the current mode ACSS/CAST connection, using the (cheap) Sharkwire interconnects, I get a similarly big soundstage to that of the UD384 and Artisan Silver cable combination; however, the resulting soundstage is rather diffused with the Sharkwire interconnects in place. Hence, I am led to conclude that the exceptionally big soundstage of the Sharkwire ACSS is a form of distortion rather than a “true” compliance with what was recorded, as it seems to be the case with the Kingrex UD384 and Artisan Silver Cables combination.

Consequently, it is a true pleasure to listen to the Kingrex UD384 with headphones; indeed, instead of feeling that the sound is somewhat stuck between your ears as many entry and mid-level DACs seem to do, you rather get the impression that the sound is originating from outside of your head, which is a far more natural way to hear things.



To be picky, I would say that what the UD384 lacks against the very best I have listened to is a truly holographic and 3D representation of the sound. If I overly exaggerate, I would describe the UD384 as being 2.5D and the AP2+dac19dsp being 3D. The UD384 USB DAC wins in the 2D size department but looses in the overall 3D impression, probably due to inferior low level detail retrieval. However, in many tracks (especially the non-audiophile ones), I preferred the rendition of the UD384 on headphone based listening.



The dynamics of the UD384 is not what draws your attention when listening for the first times to the unit. If I had to rate the dynamics capabilities of the UD384 after a short listening session, I would have said that it was adequate but not impressive.


However, after listening to the UD384 for several weeks, I can report that the dynamics of the UD384 are actually very impressive. Regardless of what type of music is playing, the UD384 sounds “alive”. While the dac19dsp can have technically better dynamics (better voltage swings?), it takes a very superior transport such as the Audiophilleo 2 to make it sing.


Overall, the UD384 is far from being boring while remaining relatively neutral dynamically throughout the audio-band. I believe that the explanation lies in its excellent handling of micro-dynamics.  

Transparency and Definition


A question that one might ask himself is: does the 32/384 capability really translates into high definition as advertised?

Before answering the question, I think it can be helpful to mention than the best measuring device I own, the EMU 0404 USB, is curiously one of the less defined and also one of the lowest resolution external devices I have tried.

So when it comes to transparency and definition, the “pixel-count” is not a reliable indicator of the outcome.


Since the UD384 uses a battery power supply, it is no surprise that it has a low noise floor (no hiss or anything). Its resolution is on par with its price tag, which means that it is much better than entry level DACs but not as good as the best I have heard.


When listening to the UD384, you get the impression that the sound is coming from a black background and depending on how revealing your downstream is what I will say below might be relevant or superfluous.

Giving the arbitrary number of 100 db as the lowest noise floor I can achieve with the AP2/DAC19 combination, I would say that the UD384 is limited to something like 70 db. It seems like a thick (black) blanket is covering the tiniest low level details that make up the recording ambiance of many recordings. While that might seem as a big difference, keep in mind that you need a pretty transparent audio chain downstream to hear those differences; if you are still using a pair of HD650s with their stock cord, there is no need to worry. However, if you have gotten to the trouble of using “high resolution” cables throughout your system and taken care of all the tweaking to increase the subjective resolution of your system, the UD384 might seem like it is lacking a little bit in absolute resolution.


With that being said, the UD384 will offer more than enough resolution in 95% of the cases. I have listened to far pricier CD players and DACs that do not approach the level of details and transparency of the UD384.


Regarding the transparency, the UD384 is a pretty impressive unit, especially considering the price. The UD384 does not seem to color in any identifiable way the music that it is playing which is an important quality for a source.




Overall, I have been positively surprised by the performance of the UD384 USB DAC when paired with its battery power supply. The unit can throw a very deep soundstage and can play with excellent accuracy and great transparency various types of music.


Considering its overall performance, its sub $700 price (with the U Power option) and the fact that you can stream music directly through USB, without resorting to an additional usb to spdif converter, the UD384 seems like an excellent bargain. In total objectivity, the amount of time and money spent on tweaking the audio-gd dac19dsp is probably not worth the increase in performance over the UD384. For anyone with a $700 budget, I would recommend without hesitation acquiring the UD384 USB DAC and its U Power supply.


Does this mean that the UD384 is as good as it gets in that price bracket? Honestly, I can’t say for sure as there are continuously new DACs being released but the UD384 seems like a safe bet. However, what I would like to see changed in the UD384 is the external casing: I would have much preferred having a one box solution, preferably on the heavy side. Many audiophiles own relatively heavy and/or stiff cables and having something as light as the UD384 might not be very convenient for everyone.



Other than that, I highly recommend the UD384 for anyone wishing to start on the computer as a source and/or willing to experiment with the effect of upsampling.


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Reply kboe
12:50 PM on February 5, 2012 
Excellent as always Amine. The good, the bad and the ugly, but all in context to paint a honest picture of performance. Plenty of references and personal bits of information make this review as good as they come. We truly have top shelf writing in Amine and Mark. Cheers to that!

As a side note, I've always had a itching to own a KingRex rig. The HQ-1 and one of their two DACs strike me as a great path toward great sound. Why does their have to be so many options! ;)
Reply Amine Slimani
2:31 PM on February 5, 2012 
Thanks for the comments on the review!

The Kingrex UD384 is not perfect but is surprisingly good for its selling price. If I had a budget of $700 for a USB/DAC source, I would choose, without hesitation, the UD384 over the dac19dsp (and assuming I didn't already own the Audiophilleo transport).
The USB implementation on the UD384 is top notch and saves you a lot of money (transport and digital cable) in comparison with many USB DACs still using (somewhat useless) off the shelf USB chips.

In this price range there is also the JKDAC which is based on a battery powered hiface supplying an ESS sabre chip. I haven't tried it but from the excellent results obtained with John Kenny's battery powered Hiface, it is probable that the JKDAC will also perform very well.

Overall, and as far as I know, there doesn't seem to be many sub $1000 DACs with excellent USB implementations. Too often the usb chip is just an afterthought.

Regarding the Kingrex HQ-1, it looks amazing and sounds interesting on paper. Srajan on 6moons said a lot of good things about in his review if my memory serves me well.
Reply Rdr. Seraphim
12:04 AM on February 7, 2012 
Battery power supplies seem to be all the rage now-a-days. Take a good DAC or S/PDIF transport and pair it with a well designed battery power supply for even better performance and sound quality. What is not obvious to some is how much better digital has always been with a great power supply. That this was well understood, actually years ago, has been lost on the zero's and one's, DACs all sound the same, and it's below our threshold of hearing, audience.

In fact, Equi-Tech published a white paper on the effects of balanced power on digital audio resulting in a reduction of jitter by 70%:

In another Equi=Tech document (

"In audio as with other digital data processing applications, AC power harmonics cause data corruption. Short of complete system failure, their is a "gray scale" effect of signal degradation that differs somewhat from analog applications. The main difference are the frequencies at which problems appear. For example in 16 bit audio, 16 bit chunks of data are processed at the rate of 44.1kHz. The bit stream rate in 16 bit audio therefore is about 700,000 bits per second (16 x 44,100.) Various other digital clocking functions may run at much higher frequencies, but they too are subject to high frequency AC noise.

How this sounds to the ear is a matter for subjective evaluation, but it is also measurable. Recent tests done on a well known manufacturer?s DAT machine revealed some interesting results. First, under standard power, peak jitter was measured under test in a live performance situation. The results yielded a peak jitter of 18ns. At the same time, the average jitter measured was 6ns. Then, the test was repeated using balanced power. The results were surprising even though they were expected. Average jitter was cut by 1/2 to only 3ns and peak jitter was cut by 2/3, down to only 6ns.

When high frequency interference is present, proportionally there will be timing errors. Digital jitter appears in a manner not unlike intermodulation distortion in analog circuits. Jitter is compounded as more equipment is added to the digital signal chain the same way low frequency noise compounds in analog systems. Digital jitter is essentially "digital hum!""

It's a rather expensive proposition to engineer an AC regulated supply that compares with the simple, but also expensive battery solution. The Hynes Regulator comes to mind, but it would require customization for a given application. One product that uses (eight) Hynes Regulators is the OVERDRIVEĀ® DAC by Empirical Audio (~ $4,000 US). Red Wine, as well as Rowland use battery supplies in their top tier products as well.

So, maybe its not so surprising that you found the best sound quality using the battery power supply. What is remarkable, as you point out so clearly, is the value proposition. We can only hope that this trend continues!
Reply rosgr63
1:15 AM on July 31, 2012 
Great review as always.
To me a properly designed and implemented power supply is very critical for any audio equipment.
When eaquipment changes it's character just by replacing the power cord it says a lot about its power supply section.