Matrix X-Sabre DAC review and impression thread

2017-06-21 09:50

DSD is all the rage these days. Despite there not being a whole lot of music available in the format (SACDs aside), DAC makers are jumping on the feature as fast as they can. And I can't blame them - aside from our "regular" music, we all love a little ear candy to show off the capabilities of our system. 
Another thing that's quite popular? The ESS Sabre DACs. These Sabre chips show up in more and more products, eclipsing the the competition from Wolfson, Cirrus, Analog Devices, and Texas Instruments in desirability and "buzz" if not sheer volume of sales. And the ES9018 is their top model. It appears in many excellent DACs including my own reference units. 
What about USB? The big thing these days is asynchronous operation, which is basically standard fare for any DAC with higher-end aspirations and is even crowding into the more affordable gear. One of the most popular implementations is based on the XMOS chipset, which is seen in many highly regarded DAC and USB to SPDIF converters. It's certainly not the only game in town but is used in enough high-end products to be considered one of the more desirable solutions.
Matrix Audio, a company which basically got their start with the $300 M-Stage headphone amp, moves upscale with the release of their new flagship X-Sabre DAC ($1099). It ticks all the boxes - DSD compatibility. ES9018 Sabre DAC. XMOS USB. Of course, none of that matters by itself - the device needs more than just buzzwords to be worthy of our consideration. Luckily the X-Sabre has more going for it.
The Matrix X-Sabre is what I'd call a "typically sized" DAC, at least in the HeadFi world. It's approximately 10" wide, 8" deep, and about 2" tall. The first thing you notice about it is the weight and construction - the unit weights 8 pounds and is CNC machined from a solid block of aluminum. You might be thinking to yourself that 8 pounds is not so much, but from a device of this size it might as well be a ton. Separate internal compartments are used for each section which supposedly helps isolate them from interference. It also isolates them from being examined in detail - the bottom panel comes off easily but the resulting view merely shows the bottom of the PCBs. I did end up removing the guts which I'll show later.
Everything on the front panel and rear panel is pretty self explanatory, so I'll just point out a few things I find noteworthy.
*There is no optical input. To be honest, I rarely use optical as a connection, and I suspect most people are with me on that. But of course there are exceptions and I imagine someone might find this to be an issue. In exchange we do get an AES/EBU input which is not always included with all DACs. 
*The unit is supported by 3 "feet" in a sort of triangular configuration. I thought this might end up making it tipsy as compared to a foot on each corner, but that hasn't been a problem. 
*The front panel LEDs are very well done - bright enough to be seen, even from a distance, but not overly bright like the majority of LEDs on audio gear. This may sound petty but for me it's kind of a big deal - so much gear has a blazing LED that lights up the room. I'd like to see all equipment handled like the X-Sabre.
*Balanced and single ended outputs are both active at all times. 
*RCA outs are a relatively common 2.2Vrms. XLR, on the other hand, is rather high at 6.8Vrms. The norm is closer to 4Vrms - Anedio D2, Resonessence Invicta, and Schiit Gugnir are all 4V. Violectric V800 comes stock at 4.3Vrms, though it can be made to go higher via internal jumpers. This high output basically means some amps won't have as much volume adjustability when paired with the X-Sabre. I didn't have any major problems myself, but some amps already have dangerously high gain, and this combo may push them over the edge for some more sensitive headphones. 
*Build quality. I just can't say enough about the fantastic look and feel of this thing. It's currently sitting in my rack next to the $4,000 Resonessence Labs Invicta, the $1,800 AURALiC Taurus, and the $4,800 Esoteric D-07. The little X-Sabre, priced considerably less than those, does not look at all like a cheaper class of equipment. In fact it's arguably among the best of the bunch. Aesthetics are subjective of course but I find its look (which I call "high-tech minimalist") to be well thought out as well as beautifully executed. 
Once the guts are removed (which is more difficult than usual but not too terrible), we can see the main components. The design breaks down to three "sections", which are almost completely isolated from each other and are connected by ribbon cable similar to what you'd find in a computer. 
The most simple is the front panel board which houses the power and source switches as well as the LED indicators. Interestingly, the LEDs themselves don't actually shine directly through the front panel. Rather, each LED shines upwards to illuminate a translucent tube (likely plastic), which then carries that light through to the front panel. This indirect lighting is why it looks so soft and non-invasive, which I love. 
Next comes the power supply board. Main components here are an array of 4 Nichicon Muse FWM 2200uf capacitors along with 2 more of the same rated at 4400uf. There are 3 LM317 linear regulators and a total of 11 ultra-fast recovery rectifiers from On Semi. Set aside in an isolated section away from the power board is a custom toroid from Noratel, which rounds out the major components of the PSU.
Last but not least we find the actual DAC board itself. Obvious bits that we already knew about - ESS Sabre ES9018S DAC chip running in quad-mono mode (4 DACs per channel). XMOS chip for USB supported by separate discrete clocks for 44.1kHz and 48kHz (and their multiples). Other things which I had been curious to find out about - a high quality, low phase noise HLX system clock at 100 MHZ. Winbond 25x40 flash memory and a PIC microcontroller for system operations. I didn't see an FPGA chip, so there probably isn't much chance of system updates.... not that the unit really needs upgrading since it already handles DSD and DXD. 
I spotted an SMSC USB3310 USB transceiver - not something I recall seeing in my other XMOS-based DACs. I was not sure why this would be used but a quick check shows a variant of that chip being present on the XMOS reference board. It seems Matrix is actually doing things "by the book" even if others have found alternatives. I don't see any dedicated DIR so I presume Matrix uses the digital receiver functionality built-in to the ES9018 itself. That's been known to be somewhat touchy in other DACs - see Yulong D18 and Eastern Electric MiniMax for examples. Perhaps this helps explain the otherwise curious omission of a Toslink input, which is known for its higher jitter. I've been using the X-Sabre with every source available and have yet to have dropouts, but I'm apparently lucky as my Yulong D18 never gives me trouble either.
The analog output stage is based around 6 of the National Semiconductor LME49710 opamps. I believe it is configured as 2 per channel for XLR, and 1 each for RCA, but I could be wrong. There's also an NE5532 floating about, though it doesn't appear to be in the main signal path. Perhaps it is used for something like impedance matching as in the Violectric gear. Takamisawa relays cover both outputs, helping avoid pops during power on or off. Overall the output stage is surprisingly simple considering the resulting sound quality. But hey, if it works, it works. 
I'm making a special section here because this is one of the big selling points of this device. The X-Sabre supports DSD64 and DSD128. You'll need playback software capable of handling DSD - JRiver and Foobar2000 are the options I tried (Windows), though others exist: Signalyst HQPlayer and JPlay for Windows, Pure Music and Audirvana Plus for Mac. Matrix provides Windows drivers for the X-Sabre as well as detailed setup instructions - JRiver is easy but Foobar is rather involved. I got it going in about 10 minutes though and if I can do it, anybody can. I confirmed that the X-Sabre uses the latest DoP v1.1 but can also fall back to v1.0 if the playback software doesn't yet handle the latest update. Also, when using the ASIO driver with Foobar, DoP is not being used. Not that it really matters as DoP is just the container and the resulting playback is still very much "true" DSD. 
DSD is not widespread but there is some material available for purchase: scroll down for a list. Of note is 2L Records which offers lots of free downloads including hi-res PCM, DSD, and DXD. Also check out where Opus3 records has a few free downloads from their two DSD Showcase albums (highly recommended). 
What about DXD? Never heard of it? It stands for digital extreme definition and is essentially a very high bitrate PCM signal at 24-bit/352.8kHz. DXD files are massive, even compared to DSD files. It's an uncompressed format (think WAV as opposed to FLAC) so that makes it even worse. For example - 2L Records has a Mozart Violin Concerto, 9 minutes and 24 seconds, available in various formats. 24/96 FLAC is 171MB. The same file in 24/192 is 338MB. The DXD version is 1GB, which is even larger than the DSD64 (274MB) and DSD128 (581MB). So DXD is nearly twice as large as the next biggest format. Yikes. An entire album (depending on the length) might not even fit on a single layer DVD. But it sounds mighty nice, and I'm always happy to take all the playback capabilities I can possibly get.
A quick word on the state of things - DSD is a major buzzword right now. DAC makers are scrambling to update firmware, or revise designs, as needed to enable DSD support. In a way, I feel it's kind of a gimmick considering how much music is actually available for these DACs in the format (the answer being not much at all). However, at the same time I also feel it's kind of an important feature to have. Remember that the SACD format used DSD so there are quite a few albums out there already in the format. As time goes by I think we'll be seeing more and more releases become available. 
No matter what the audio mags and websites tell us, SACD was a failure in the grand scheme of things. There hasn't been a plant pressing SACDs in the USA for years, and there are hardly any dedicated SACD players being made these days. On the other hand, universal disc players are rather common, and there was something like 6,000 SACD releases in total. Even counting some of those as being mere PCM to DSD conversions, and some being multi-channel rather than stereo, that still leaves quite a few titles usable by the regular 2-channel music lover. As HDtracks and other sites look to increase sale, and notice all these new DACs with DSD playback capabilities.... it only makes sense that they will scramble to get more DSD downloads ready to go as fast as possible. People who already own the 16/44.1 version of a song might not feel the 24/96 version is worth the money to re-buy. But maybe they'll feel like DSD is a big enough improvement. I can guarantee that HDtracks is thinking that very thing. Perhaps DSD can have a second renaissance via downloads where it failed the first time around on physical media.
So where does this leave us? Simply put, DSD is not enough on its own to justify buying a DAC. It might be more and more relevant as time goes by, but redbook playback is still the defining characteristic of any DAC. Having said that, the situation reminds me of 192kHz USB support: I've had people specifically tell me how such-and-such DAC was perfect for them but they couldn't buy it because USB topped out at 24/96. I ask them if they have any 24/192 material in their library, and they reply "no, but someday I might". 
A quick note about service: the X-Sabre is available worldwide from the global Matrix website. Customers in the USA (and probably Canada as well) should go through the North American distributor. US distribution is handled by a fellow named Arthur who I can vouch for - we've been chatting since long before he picked up the Matrix line, and he's always been very informative and helpful. Orders through his site are drop shipped directly from China, but all service would go through him. So if you had questions about anything at all - for example, needing a walk through due to driver issues, or DSD playback, or whatever - he'd be there to help. Or in the unfortunate event of a hardware issue, the unit would be mailed to him in New Jersey rather than back to China. I know RMAs are one of the sticking points for people who prefer not to order gear from China, so a helpful local distributor is great news in my opinion. Having him be a nice guy and a native English speaker is even better. 
I used the following gear during my evaluation of the Matrix X-Sabre, down to the last excruciating detail because some people have asked for that:
Source: Auraliti PK90 USB server powered by NuForce LPS-1 power supply, connected direct over USB or else routed through an Audiophilleo AP1 with PurePower, Acer laptop running Foobar2000 or JRiver Media Center, Cambridge Audio 740C
AMP: AURALiC Taurus, Violectric V200, Icon Audio HP8 MkII, Firestone Audio Bobby, Analog Design Labs Svetlana II, Stax SRA-12S
Headphones: Sennheiser HD800, Stax SR-007 MKII, Audeze LCD-2.2, Beyerdynamic T1, Thunderpants, Frogbeats C4, Cosmic Ears BA4, Heir Audio 8.A, Sensaphonics 3MAX, JH Audio JH13pro FreqPhase, 1964 Ears V3
Power conditioning: CablePro Revelation, Yulong Sabre P18
AC cables: CablePro Reverie, Charleston Cable Company Auric Ohno
Interconnects: Charleston Auric Ohno, NuForce Focused Field, Signal Cable Analog Two, Pailiccs Silver Net
Digital: NuForce Precision coax, Charleston Auric USB
Headphone Cables: several models from Toxic Cables, Beat Audio, Charleston Cable Company, and 93 East
I knew people were curious about my impressions, and I had been held back from doing serious listening of the X-Sabre while I finished up my review of the NuForce DAC-100. So once I was ready to focus on the Matrix unit, I didn't mess around. I launched straight into some serious listening on the best gear I have in the hope that I would quickly lock on to the character of this device. As usual, life got in the way, and it's taken longer than I had hoped.
My first serious notes from listening to the X-Sabre can be summarized like so - clean, resolving yet slightly relaxed presentation with smooth but extended highs, great timbre, and a nice sense of coherence from top to bottom. That pretty much sums it up and you can stop reading right now if you want. Or not.
In the school of DACs, there are a few archetypes that most people are familiar with: There's the overly slow, warm, syrupy type. There's the hyper detailed, analytical thin type. Everything else falls somewhere in between those two, with most leaning more towards one side or the other. Very few are absolutely in the middle, and those tend to be on the expensive side anyway. Not to mention most people have a hard time agreeing where exactly that middle ground lies. 
The Matrix X-Sabre is not quite in the middle. To my ears it leans a bit towards the so-called "musical" side rather than the more dry, analytical side. Thankfully it avoids many of the downsides of its musical brethren - it's not slow, not rolled off in the least, doesn't have mushy bass, and doesn't impart too much coloration onto the sound. It also avoids many of the downsides of the analytical type - it's not etched and harsh on the top end, and it's certainly no lightweight on the bottom. Best of both worlds? Not completely. Some DACs have better detail retrieval, some have more textured bass, some have a more clear, transparent presentation. But overall I'm very pleased with the X-Sabre. $1100 is not cheap but in the grand scheme of things it's not a vastly high price for a DAC. Some compromise was necessarily involved, and Matrix seems to have done a good job prioritizing. 
Those last few lines might just hold the key to explaining why I like the X-Sabre so much. As I survey the competing DACs in the $800-1500 range, I can generally find one that outperforms the X-Sabre in any single aspect. Yet very few of them can perform so collectively well in all areas. There are many analogies that might apply here - the well balanced athlete who might not headline a Nike commercial but nevertheless has a long and fruitful career, earning many millions of dollars in the process and being well respected by peers and fans alike. Or how about the neighborhood restaurant that you love, with a widely varied menu - they don't specialize in any one area so it is possible to find a better steak, better pasta, better fried chicken... but those come from specialty places which don't have near the selection of your favorite spot. I could go on and on but hopefully you get the point - the X-Sabre is really good across the board, if not quite the best at any particular aspect. 
A few more noteworthy things to mention:
*Soundstage is very impressive. It's got that nice open feeling that proves elusive even for many expensive DACs. If the X-Sabre was going to stand above the pack in any one specific area, this would be the one. 
*Warmth. As I'll continue to explain, the X-Sabre is slightly on the warm and smooth side. It's not a rolled-off tubey NOS sound or anything of the sort but it does help take some of the "bite" way from certain recordings - in a good way. I don't feel like I'm missing much in terms of attack on well recorded tracks, but harsh sounding mediocre recordings do get a gentle helping hand. I did notice some treble glare in the early hours of listening but this seemed to fade as I clocked more time on the unit. Perhaps it never completely went away in the grand scheme of things (as compared to my Resonessence Labs Invicta for example) but it's not something that bothers me now, after several hundred hours.
*Input differences. I mainly used USB connected to my laptop. It sounded really good that way. It took a lot of effort to improve on it with a USB to SPDIF converter - the Stello U3 sounded worse, with a slightly more edgy feeling that threw me off a little. It wasn't terrible but it did lose some of the charm as opposed to the USB input. The Resonessence Concero used as DDC is very difficult to discern from the native USB input, at least when used in the standard mode. When applying the proprietary Resonessence upsampling filters (IIR or apodizing), small changes in character are present. I particularly like the minimum phase IIR filter in this case but it's nothing so large as to justify the $599 Concero being a mandatory add-on. Finally, I went all out with the Audiophilleo AP1 with PurePower battery option. That combo did raise the bar in terms of transparency, imaging, and fluidity of the midrange and upper mids. I enjoyed it but when it came time to return to the native USB, I didn't find myself going through withdrawals or anything. Lastly, I tried my Cambridge Audio 740C as transport over coax and optical cables. X-Sabre again sounded more edgy, much like when I used the Stello U3. It wasn't bad sounding in absolute terms and if that's all I had available I'd definitely still enjoy the device... but I just enjoy it more through USB. I didn't have a chance to use my JF Digital music server which has less jitter on the SPDIF output. It might have sounded closer to the USB, but I was too lazy to move it out of my living room system. 
*I don't notice any difference between the RCA and XLR outputs, aside from the higher XLR output voltage which I mentioned earlier. It's possible that some minor difference exists, but if so it's small enough to be inconsequential in my opinion.
I spent a lot of time listening to some exceptional DSD tracks. The Opus3 Records DSD Showcase albums are definitely worth buying if you want some demo material. At $12.99 for DSD128 and a mere $9.99 for DSD64, they are a definite value compared to some of the overpriced hi-res albums out there. I'd still enjoy "Where the Green Grass Grows" by Eric Bibb even if it was a low bitrate mp3 file.... but this DSD version is perhaps one of the most lifelike recordings I've heard, anywhere, ever. I spent most of my time with the DSD128 version because hey, why not? To be honest, the DSD64 version sounded similarly excellent, to the point where I'm not sure I can reliably tell them apart. But I didn't specifically try so that's a story for another day. Both of them have rich tones, lifelike airiness, pinpoint imaging - your name an audiophile cliche, and it's in this track to a very high degree. I was also exceedingly impressed by The Erik Westberg vocal ensemble & Mattias Wager – Nun kommt der Heiden Heiland, which has some killer organ that really plumbs the depths. The lows on this track will lay bare the differences between a reference caliber headphone - LCD-2, 8.A, SR-007, JH13, etc, and one that is merely "pretty good" - W1000X, HD650, DT880, etc.
Not to be outdone, DXD tracks sound very nice too. I have Quiet Winter Night by the Hoff Ensemble, which like many recent hi-res releases was originally recorded in the 24-bit/352.8kHz DXD format and later converted to DSD or various PCM options. I have a hard time believing DSD can be any better because the DXD release is already spectacular. I got this album as a promo - one of the best parts of becoming a "real" audio journalist - but I only have this one version. If I was buying, I'm not sure I'd want to pay almost double for the DXD as compared to the plain ole' 24/96 FLAC version. Then again maybe I would if the difference was noticeable. This sets off an interesting discussion about why this price discrepancy exists for download versions - but I won't get into that here.
What about hi-res PCM, which is practically becoming yesterday's news in light of these new DSD/DXD options? It still sounds great on the X-Sabre. All of my usual reference material was highly enjoyable - Conga Kings, Traffic by CBW, Wilson Pickett, Norah Jones... if one never listened to any DSD, this DAC is still very impressive.
Then we come to "boring" Redbook quality material, which still happens to make up a huge majority of the music in our libraries. Isn't it of limited quality and difficult to listen to after all that amazing hi-res stuff? Yes and no. By its very nature, hi-res releases in all formats tend to be some of the best recordings out there. Yes, there's the occasional sneaky upsample, and some modern popular releases that make no sense to buy in hi-res due to their inherently poor dynamic range. But those are the exceptions - most hi-resolution material also sounds very good in the standard CD release. In contrast, stuff that only ever came out on CD can be rather mediocre or sometimes downright terrible. Stuff like Rush or Red Hot Chili Peppers is especially annoying when the music is enjoyable but the recording is not. Yet many counterexamples exist - try the Steve Hoffman Metallica DCC remasters, any Hiromi album, any Yo-Yo Ma album, anything from Reference Recordings, most albums by Peter Grabriel or Genesis, almost any Miles Davis or Otis Redding or Alison Krauss & Union Station or Bill Evans or.... you get the idea. Redbook material can sound downright bad but it can also be very, very good, and we should be careful not to place all the blame on the format. The X-Sabre handles the good stuff really well, and due to its slightly smooth character, is better than many when it comes to the bad stuff. I guess what I'm trying to say here is that great recordings exist in many formats and the X-Sabre can pretty much play them all.  
Rather than going any further down this road, I want to switch gears and talk about some specific comparisons with the various DACs I have at hand. This will hopefully prove illuminating for someone trying to decide between two contenders, as well as helping flesh out the performance characteristics of the X-Sabre. I used a lot of gear for my general listening, but for these specific comparisons I used my electrostatic setup consisting of a Stax SRA-12S with the Stax SR-007mkII. The SRA-12S (recently worked over by Spritzer and given a Pro output) is an old-but-still-very-nice Class-A solid state unit which to my humble ears is superior to many of the current production models including the SRM-727II. Stax intended it to be a preamp as well which means it has plenty of inputs - perfect for comparing several DACs in the same system. Care was taken in terms of level matching (which is no fun but very necessary for proper comparison).
NuForce DAC-100: I just finished reviewing this DAC and it's very enjoyable overall. At $1100 it is a direct competitor for the Matrix.There are some obvious differences in terms of features - Matrix gives you DSD capability and balanced outputs while NuForce has a headphone amp and preamp capabilities. Obviously these different feature sets will each appeal to a different user.
Strictly focusing on sound quality from the DAC section - these are totally different sounding devices. The NuForce can be summarized by the words "lively", "exciting", and "dynamic", but it isn't the last word in micro-detail or gracefulness. The X-Sabre has better detail retrieval and a smoother, more relaxed presentation that flows more easily. They both have their unique moments to shine - the DAC-100 better captures the scale of The Planets by Gustav Holst, or the intensity of heavier acts such as Shai Hulud or Stretch Arm Strong. In contrast, the X-Sabre is better at revealing the quirky/brilliant nuances of music from composer Harry Partch, allowing me to better notice the interesting rhythm and (micro)tonality of his complex works like Delusion of the Fury. It also excels with technical metal - Meshuggah, In Battle, Becoming the Archetype, Opeth, Theory in Practice - while these bands are all undeniably heavy, their music is also very complex, and the X-Sabre resolves their detail better than the NuForce while at the same time maintaining a non-harsh sound (which is welcome since these bands don't always make the best recordings). It's not that the DAC-100 sounds bad with these, but the X-Sabre just does it better. Your system, music, and preferences will determine which might work best. Well recorded stuff from Norah Jones or Patricia Barber or Frank Sinatra will sound really nice on either DAC, but vocals are more penetrating and real with the X-Sabre. Both are still very enjoyable. 
Which one do I like more? That's tough. The value proposition of the NuForce is hard to deny - DAC-100 plus HD800 and you've got a simple but great sounding setup. Then again, people shopping for a DAC in the $1000+ price range might already have eyes on a nice stand-alone amp, negating the benefit of that integrated amp. If we leave out build quality, looks, functionality, etc and focus purely on sound quality as a DAC, I'd say the X-Sabre takes the lead, at least in my system and with the music I prefer to listen to. If I primarily used coaxial SPDIF rather than USB, my choice would not be as clear, as the NuForce sounds the same on those while the Matrix goes down a notch compared to USB. 
Resonessence Labs Concero: This little unit is probably not on the radar of most people looking for a $1K DAC. Maybe it should be. Obvious feature differences aside, the Concero comes surprisingly close to the X-Sabre. The Matrix comes out ahead in areas like treble realism, midrange openness, and soundstage depth. X-Sabre seems to be a little smoother too. Surprisingly, the Concero keeps up in the lower regions with excellent bass texture and realism - so much for the idea that beefy power supplies always equate to superior bass. But overall when using a really nice headphone like HD800, Stax, JH13, etc, the X-Sabre pays dividends in overall realism. It's just more convincing in that "last bit", audiophile sort of way. That said, if you want to spend less money and don't have a need for balanced outs or DSD playback, Concero is an excellent choice. 
Musical Fidelity M1A: I don't care that this DAC won various awards in magazines - I dislike it immensely. To my ears it sounds blurry and indistinct while at the same time being harsh and splashy on the top end. I guess that's an impressive accomplishment in a way... X-Sabre is far superior to the M1A in every category. OK, the Musical Fidelity unit is $350 cheaper, but if money is an issue I recommend the Concero without hesitation. It's even cheaper and still sounds better too. 
PS Audio NuWave: I didn't really care for this one either. It certainly looks great and has a nice balance of features for the money.  I really wanted to like it. But the sound.... it just seemed a bit too bright, too plastic, too thin. I imagine some people like this sort of thing and hear it as extra detail but for my taste it was just too much. X-Sabre has a far more natural tone and still has plenty of detail - in fact it does cymbals in a significantly more realistic way. Just because they are boosted, doesn't mean they sound real, and that's where the NuWave gets it wrong. At $999 or even at the discounted $799 price I already see in certain places, there's no way I could recommend the NuWave over the X-Sabre. PS Audio might sell a ton more than Matrix due to their name brand, but my recommendation lies strictly with the X-Sabre.
Violectric V800: I love the V800 - it's got a neutral, clear sound without being sterile or harsh, and it still has enough soul to move me. It's one of my favorite DACs at any price, period, and proves to be tough competition whenever I review a new DAC. In comparison, the X-Sabre is very close in quality but with a different flavor. It's a little smoother but also bit less resolving of tiny details. That's the main difference - X-Sabre has more perceived warmth, which can make it easier on the ears with mediocre recordings, while V800 goes a little farther with reference quality material. At times I felt like the V800 made the X-Sabre seem a little "glassy" in the highs, but I could never get this to be a consistent thing. Soundstage on X-Sabre is about the same in width but has the slight advantage in perceived depth. The trade off - V800 has more accurate imaging. This soundstage/imaging difference is only really noticed when using an excellent chain of equipment though. Once again the feature differences are split down the middle, so either of these units comes highly recommended by me. 
Yulong D18: The D18 has been my favorite "budget" ES9018 based DAC for a while now. From the balanced output, it's more exaggerated than the X-Sabre - smoother and warmer. From its RCA outs, it is more neutral. It's great to have both options, but the X-Sabre offers a nice middle ground presentation between the two, while being a bit more resolving than either. Bass is very slightly more extended if not quite as prominent as D18 via XLR, and top end detail is more believable, though at times the D18 would be a better match for some systems, especially for people who are extremely sensitive to any kind of treble glare. The differences are not huge though - D18 is still a very good DAC and at $699 it remains a great value. It has no USB input but a good DDC can be had for a reasonable price, allowing the combo to still be as cheap or cheaper than the X-Sabre. But overall the Matrix unit is slightly better as a whole. Should D18 owners bother to "upgrade"? If they are pleased with their unit then I'd say probably not. The X-Sabre is not really different enough to warrant a switch. The exception would be if someone had a D18 and was mostly pleased with it, but found it a little too smooth on the top end in balanced mode. I've talked to several people who felt that way but at the time had nothing else to recommend to them. Now I do. 
Anedio D2: This is where the X-Sabre is finally outclassed. It's not by a massive amount, but I do feel the D2 is in another league in several areas. It's got better leading edge definition, superior low frequency texture, and more transparent midrange too. But it also costs $400 more which is around a 36% increase in price - that's substantial. And some people may actually prefer the slightly warmer X-Sabre sound depending on their system. In order to upgrade from the D1 without a major price increase, Anedio used a less costly enclosure for the D2, and it shows. It's still attractive and all, but the X-Sabre looks and definitely feels like it should be the more expensive product. And the Matrix unit is available right now for order while Anedio is constantly sold out with a potentially long wait. I'd never talk anyone out of buying one of my favorite DACs and if you can afford it (and can wait for it) by all means put the D2 on top of your list. That still doesn't minimize the quality of the X-Sabre. 
Others: Without specific comparisons, I'll just say that I prefer the X-Sabre over some well known and well regarded units like Benchmark DAC-1, Bryston BDA-1, Rega DAC, Wyred 4 Sound DAC1, North Star Essensio, Grace Design M902, and Lavry DA-10. To my ears the X-Sabre sounds better than most of those, or in a few cases sounds similar but costs way less. I know this is vague but I don't have any of these on hand right this moment so I can't get down to the nitty-gritty of each one.
Ever browse for an Android tablet and notice some of the "off" brands out there? There are plenty of them which seem to have unbelievably good specs - quad core CPU, lots of memory for both RAM and storage, SD card slot, HDMI out, large screen with great resolution, the latest Android build, replaceable high capacity battery.... essentially everything you could possibly want. And the price will tend to be significantly less than models established brands like Asus, Samsung, or Acer. Despite all the specs and features, my experience with these types has yet to pan out. There's always a catch somewhere. Maybe that screen with the great specs actually has a poor viewing angle or dull colors. And maybe their Android install is packed full of non-removable bloatware. And maybe that so-called "high capacity" battery only nets a few hours of real-world use. And maybe that 1.5 GHz quad core CPU can only comfortably manage 1.0 GHz before having heat issues. My point here? Shopping with an eye towards features per dollar is not always advantageous. 
Fortunately, the Matrix X-Sabre avoids that sort of thing. Yes, it does have a lot of things going for it - top level ES9018 Sabre DAC, balanced outs, impeccably built enclosure, XMOS asynchronous USB, and DSD capabilities. But at the core of the device is really good sound. Without that, features become little more than gimmicks, and the perceived value rapidly diminishes. With it, features actually become relevant, and value is added.
I recommend the Matrix X-Sabre for anyone who wants a well rounded DAC in the $1K price range. Is it the best DAC out there? Of course not. I can point to other DACs with better performance in various areas and by all means - if you're a detail freak or want an ultra-smooth NOS sound or have any other specific attribute that you value above all others - the X-Sabre, as a jack of all trades (but master of none as the expression goes) might not be your ideal match. Yet for overall competence I can't think of another unit to recommend more highly for the price. Add in local service and support from the new US distributor, and you've got yourself a winning package. Highly recommended.  
Note - this thread started as informational and went for a long time before I actually got the review posted. Reading in a linear fashion might not make sense at times, since I edited the first post to include the review. 
An update - Grant fidelity is now the official distributor for the Matrix gear in Canada. US customers still use the Matrix USA website. I know this DAC is available elsewhere, including eBay, but I highly recommend using the local distributor if at all possible. It's worth it - if you have an issue with your device, would you rather ship back to China, or to a local agent in your area? Also, any questions regarding use or anything else can be better answered by the authorized distributors in my experience. 

Another minor update - the X-Sabre is available in silver now, and all models now have universal voltage (selectable via dip switch on the bottom).