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USB DAC shoot-out

USB logo made up frm pictures of USB products.

USB ups the ante

[Italian version]

Product: SuperPro 24/192 USB DAC
Manufacturer: DIYKits.Com
Cost: 85 UKP (YMMV)

Product: KingRex UD-01 USB DAC
Manufacturer: KingRex
Cost: 150 UKP (YMMV)

Product: KingRex UD-01 'SE' USB DAC
Manufacturer: KingRex but modified by Item Audio.
Cost: 225 UKP

Product: KingRex Power Supply Unit
Manufacturer: KingRex.
Cost: 165 UKP (YMMV)

Product: DevilSound USB DAC
Manufacturer: Devilsound
Cost: 210 UKP (YMMV)

Product: Locus Polestar USB Cable.
Manufacturer: Locus Design Group
Cost: 195 UKP (YMMV)

Product: CryoParts Custom USB Cable.
Manufacturer: Cryo Parts.
Cost: 75 UKP (YMMV)

Reviewer: Nick Whetstone - TNT UK
Reviewed: April 2009

I think that we can safely accept that PC audio is not only here to stay, but fast becoming the preferred music source for many audiophiles. So it is not surprising that the choice of equipment that can transfer the music from a hard drive to the hi-fi system is now quite large. In this review, I'll be casting an eye (and a couple of ears) over three USB DACs, together with a few accessories to use with them. All the equipment for this review was loaned by Item Audio in the UK, who specialize in PC audio.

For this review, I'll be using the DAC's with an AMD Athlon based PC running Ubuntu, and using the Banshee and Exhail music players (Item Audio also strongly recommend Songbird for Ubuntu). I used this set-up in two systems: one using the Autocostruire TubePre, Monrio MJ amplifier and Mordaunt Short Pageant 2 speakers. The second system consisted of a Pedja Rogic Jfet buffer, Resurrectored chip amp, driving Hawthorne Audio Duets, and with an active crossover/solid state amp for the woofers on the Hawthorne Duets.

Super Pro 192/24 USB DAC. First up is the SuperPro 24/192 USB DAC. This is what Item Audio say about it.

Though superficially resembling the fag-packet form factor of the KingRex UD-01, the likeness is skin deep: this little DAC is built for speed and resolution, featuring Cirrus Logic's CS-8416 receiver ship and their ultra detailed flagship 24bit 192kHz, CS-4398 D/A chip. At half the price of the KingRex DAC, it also represents incredible value.

It will work with an iPod or any PC, regardless of operating system.

Right from the off, the SuperPro is impressive. Impressive in the amount of fine detail it produces. It's sound is bright and sparkly (but certainly not over so). Detail retrieval is very good and it does that 'layers' thing where you get a very good range of tone. It's musical, and grabs the attention. Sound-stage is large and imaging very clear. But like the previous USB DAC's that I have tried, I found it a bit lightweight in the lower octaves. Not quite as much as the others, but I wouldn't describe it as 'full-bodied' particularly when compared to the Devilsound DAC and the KingRex UD-01. If you like a lot of rock music, this may not be ideal for you. It's not devoid of bass, and what there is, is quite tuneful. But after listening to the other DACs in this review, and my SB3 set-up, it is slightly bass light and there's no getting away from that.

KingRex UD-01 USB DAC. Second up is the KingRex UD-01. A slightly more conventional enclosure than the SuperPro as you can see from the picture. Again, I'll let Item Audio describe this DAC.

Representing a significant step up from the Digital-Analogue Converter built into the KingRex T20-U amplifier and the tiny SuperPro DAC, the petite UD-01 delivers a strongly musical 'non-digital' presentation thanks to the (TI) Burr-Brown OPA2604 which acts as an output stage pre amp removing digital nasties and smoothly sculpting the analogue stream. This chip is socket mounted and can be upgraded or swapped out according to the user's preference.

The primary chip is the Burr-Brown PCM2702E mated with a large internal buffer for audio packet storage, effectively re-clocking the input stream.

If I was beginning to think that USB DAC's were not for me as they sounded a bit 'light', the KingRex changed that idea straight away. But it's not just in the bass department that it works well, it's very impressive in all departments. If anything, I felt that the SuperPro perhaps did fine detail better than the KingRex, but sometimes when something lacks a bit of bass, it can sound more detailed higher up. The sound is a long way from the old 'digital sound' that was associated with many CDPs. I won't say it sounds like a turntable, but you would have to be very fussy to complain about it sounding 'digital'. Like the SuperPro, the sound stage is massive, and there is great detail that brings out the ambience on certain recordings. The amount of detail is fantastic! I don't recall hearing the Q -sound effects on 'Amused to Death' (Roger Walters) quite so clearly, and as 'detached' from the speakers. The music just flows from the speakers, helping you forget the equipment and enjoy the performance. The balance is very good with plenty of bass and a good top-end. No need to 'tune' your system to fit the UD-01 in! Everything that I played through the UD-01 sounded great. And it didn't get tiring with extended auditioning.

I've read that some people don't rate the UD-01 very highly when powered from the wallwart PSU. However I was still quite impressed, possibly due to running the whole system through a very good power conditioner. I've found in the past that the cheaper wallwart PSU's (particularly the switched-mode type) can be affected by how good (or bad) the mains supply is. Unfortunately, I didn't come across the wallwart comments until after returning the UD-01 so couldn't listen without the conditioner.

The obvious next step was adding in the KingRex power supply. Best described as neat, compact, and inconspicuous, this heavy little box of tricks comes with a detachable umbilical lead to connect it to the UD-01. Here are the specifications.
KingRex PSU.

The price of the PSU at around 165 UK pounds may cause some to ask if it is worth the extra outlay, given that it costs more than the DAC itself. I've had similar questions about power supplies for the Logitech SB3 but the bottom line is, power supply quality is absolutely crucial to sound quality, and good power supplies are not cheap. In this case, the addition of the power supply to the UD-01 clearly makes an improvement. Macro detail is increased and the bass gets tighter and a little deeper. Is it worth it? Well that's a question only you can answer depending on your financial situation. If I had a UD-01 and wanted the best sound that I could get out of it, I would certainly be looking to upgrade the wall wart that is supplied as standard because a 'better' power supply clearly works on the UD-01 (as it does on most hi-fi). If you are tempted by the KingRex PSU, I would also suggest that you look at the SR1 PSU from Paul Hynes Audio that is only a few pounds more.

The next step was to try Item Audio's 'SE' version of the UD-01. Item have replaced both the opamps in the UD-01 after auditioning as many opamps, and combination of opamps, that they could get their hands on. Their 'winning' recipe was to use two pairs of OPA627 opamps (on adaptor boards) in place of the OPA2604 (not a great opamp in my experience), and the TL072. And this is clearly an improvement on the stock configuration, sounding better in almost every department. It simply sounds more sophisticated than the stock UD-01. It's not difficult to swap the opamps in the UD-01 as they come located on sockets, but if you decide to follow Item Audio and use OPA627's, you will need to get hold of adaptor boards so it is not quite a 'plug-and-play upgrade! Item Audio are constantly working to improve the 'SE' so the specification will change in future. If you are not into opening cases and 'fiddling' then I can recommend the 'SE' as a worthwhile upgrade over the standard UD-01. The 'SE' was auditioned with the up-rated KingRex PSU.

Devilsound USB DAC. Well I can honestly say that I was enjoying the music produced by both the SuperPro and KingRex UD-01 so much that it was difficult to move on. Sitting in the carton that had come from Item Audio was what looked like an empty padded envelope . Actually, this contained the Devilsound USB DAC that is so diminutive it hardly made a lump in the envelope. I knew already that the Devilsound connected between the PC and hi-fi, and was powered from the PC, ie it had no external power supply, not even a wall wart, never mind something more up-market. But reviewing is reviewing so I connected it up and returned to my listening seat. Well, I couldn't believe my ears! If I hadn't just plugged it in myself, I would have accused who ever did so of playing a trick on me. The sound is simply amazing even though it is powered from inside the PC! As with the KingRex UD-01, there is absolutely no shortage of powerful bass - and it's very tuneful too. It's the sort of sound that just grabs you because it is quite a 'strong' presentation albeit pleasant to listen to. How is it possible with a supposedly noisy power supply from inside the PC? And how does such a tiny device make such a big sound? Perhaps the designers sold their souls to the Devil and that's how it gets its name? Well if you go to the Devilsound web site, they actually explain how they have achieved what they have.

For the technical, here are the basic specifications of the Devilsound DAC.

The Devilsound comes in a tiny aluminium enclosure that actually looks quite classy considering it's diminutive size. The quality is continued with the addition of Eichmann Silver Bullet RCA terminations. All in all, it's a well though out package that has a quality feel about it.

So, does the Devilsound sound better than the KingRex UD-01? Different certainly, and with the upgraded power supply, the KingRex just shades it with slightly tighter bass and a little more 'air' and minute detail. The Devilsound sound is more 'up-front' (possibly a little too upfront for some tastes) has great timing but ultimately just lacks a little 'subtlety' for me. It's great fun to listen too but with longer auditioning I tended to miss the subtle cues that I get from my SB3/DacKit combination (and the KingRex UD-01). The SB3/DacKit also beats the Devilsound (and KingRex) when it comes to sound stage depth but there's not much in it!

The up-rated PSU takes the KingRex package to 295 UK pounds compared to the 210 UK pounds for the Devilsound. Choosing one of these items is going to be as difficult as choosing a CDP was, and if you can, I advise you to try and listen to as many as you can before you part with your money. What we can do as reviewers, is narrow down the field, and to date, the KingRex UD-01, and Devilsound, are by far the best USB DACs that I have heard. They are also the ones that would make me consider moving away from the SB3/external DAC that I use now if I could have the level of convenience that I have with the Squeezebox set-up!

Cryo Parts Custom Cable USB cable. Item Audio also provided a pair of USB leads that are claimed to be an improvement on the stock USB leads that have traditionally (can I say traditionally about anything computer-related?) connected printers, scanners and cameras to a PC. If you cut one of those basic leads open, you will find four wires, two that carry the 5 volt voltage, and two that carry the data. The one that I dissected didn't even have the wires twisted!

The first of the supplied cables that I tried was the CryoParts Custom USB Cable, a shielded type that has been cryo-treated, and comes in a smart black braided sleeve. Plugs are the standard items but how long will it be until somebody comes up with a gold-plated 'SE' version? Whatever they do come up with won't be good enough in my opinion. I find USB plugs almost as frustrating as SCART plugs to plug in! But how did this cable sound? To be totally honest, I'm not sure if I heard enough difference between that cable and a bog-standard USB lead to be sure that it was worth the price. There may have been the slightest of improvements but I couldn't even be sure of that.

Locus Design Group Polestar USB cable. So I wasn't expecting much more from the other cable. That was the Locus Design Group Polestar USB Cable, 0.5 metres in length with a very similar appearance to the Cryo Parts cable. But I was in for a surprise. The sound using this USB cable was clearly better. There was just a bit more of everything. Tighter bass, more detail, more 'air'. So what is special about the Polestar cable? This what they say about it:

This is not a reworking of an existing mass produced cable: this is an entirely new design using bespoke DCT-OFC wire and hand built by Locus in America. Close attention is paid to mitigating mechanical noise and triboelectric effects. The cable comprises a special braid of ultra pure DCT-OFC conductors and Teflon air tubes sleeved in a tinned copper weave and strategically located ERS fabric for shielding and additional damping. Finally, a layer of multi filament nylon is pulled over the complete assembly for extra damping and a handsome finish.

I suspect at least some of the improvement is down to the claim that the signal and power wires are somehow more isolated from each other, and shielded too. The bespoke wire probably helps, and possibly the cryo treatment too.

But it's not a huge improvement and this cable will come into the category of modifications to which we apply the law of diminishing returns. To be more frank, I can't really justify such a price for a USB cable even though it does make a noticeable improvement! Look at it another way, you get a similar amount of improvement from the KingRex PSU that costs less and obviously costs far more to produce than this USB cable. But if you are looking to squeeze the last drop out of something like the KingRex UD-01 (or 'SE' version), it does do that! As ever, the customer decides but I would suggest an audition in your own system before you make up your mind about this USB cable.

So what did I learn from all this? Well firstly that USB DACs are moving ahead in sound quality. USB may not be the best way of getting music from a computer to a hi-fi system (Firewire is reputed to be better) but what you can get now, with items like the KingRex UD-01, and (to a lesser degree) the Devilsound, is a level of performance that is on par with CDP/DAC's costing well over a 1000 UKP. Given the prices, that has to be a good thing for those of us with less outlay to spend on hi-fi. And I suspect that even those with very expensive CDP/DAC's would be tempted to buy something like the UD-01 'SE'/PSU/Polestar cable. For myself, I feel that the sound quality of the UD-01 with all the 'extras' is possibly slightly better than I get from my modified Logitech SB3 with an external DAC. But I won't be rushing out to buy a USB DAC just yet because using one is a lot less convenient than using the SB3. I need a second computer running (close to my hi-fi), there is no remote control (although you can use a wireless mouse to give you some sort of armchair control). What's needed to make USB DAC's really useful (IMHO) is some sort of remote control system. Yes, you can buy a PDA and have that control the PC feeding the USB DAC. But that's currently a job for the geeks, and certainly not a simple plug-and-play solution. You could be messing round for months trying to get it all to work together (if you ever do)! The SB3 on the other hand just sits there, connected to my main PC that is running anyway (no waste of power), and a simple remote control gives me easy access to all my music. When it gets that easy with USB, then I'll be very tempted to buy something like the KingRex UD-01 'SE'!

OK, you can tell that the KingRex UD-01 was my favourite out of the USB DACs tested here. More accurately, I should say that the UD-01 'SE' was my favourite. But I can't finish without expressing my sincere admiration for the Devilsound and its miracle of miniature (or should that be micro?) engineering. And don't write off the Pro Sound 192/24. In its price range it is easily the best USB DAC that I've heard, clearly out-performing the Trends UD-10 and the Style Audio HDIV. So a good bunch of USB DACs and if you are lucky enough to live within a reasonable distance of Item Audio, I can strongly recommend that you pop in and take advantage of their vast knowledge of this sort of item. One thing is for sure, and that is PC audio just keeps getting better! When I compare the sound quality of these USB DACs against CDP's of a similar price from a few years ago), the USB DAC's are way ahead! Once again, my thanks to Item Audio for supplying the gear for this article.

© Copyright 2009 Nick Whetstone - nick@tnt-audio.com - www.tnt-audio.com

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