Singxer SU-1 USB Bridge


Headphoneus Supremus
Pros: Impeccable sound quality, solid build, lots of outputs, amazing value
Cons: Availability is somewhat limited at the moment
Not too long ago, USB audio was considered a joke by most "serious" audiophiles. And to some degree they were right - most early USB capable DACs had very poor implementations, which meant computer audio prioritized convenience over sound quality. Think Spotify which is great for music discovery or background entertainment but not really suitable for critical listening.
Fast forward a few years. The USB inputs on a lot of DACs began improving to the point of competing with, and sometimes managing to outperform, their SPDIF counterparts. Asynchronous chipsets became widespread and brought lower jitter along with 24/192 capabilities. Around this time we also saw the proliferation of dedicated audiophile playback software. Computer audio had hit the mainstream, keeping in mind that this is still a niche hobby and nothing will ever really be "mainstream" in the true sense of the word. Regardless, USB was no longer a pariah input, and rare was the DAC that didn't have at least fairly decent USB capabilities.  
Then came the rise of the DDC, or digital-to-digital converter. The point being that USB audio was progressing at a rate far quicker than DAC chips, power supplies, or analog output stages, all of which have been fairly mature for many years. A good DDC allowed one to raise the level of their DAC without throwing the whole thing out and starting over. While solid USB implementations were common, it was still rare and expensive to find devices with true reference-quality USB solutions on board, with attention paid to the tiniest details. 
I had a great time with DDCs in general. The Stello U3 was a solid performer for a while, beating all competition until the revolutionary Audiophilleo 1 with PurePower took up residence in my main system. That duo was superb - even very expensive DACs from EMM Labs and Esoteric showed improvement with the AP combo in play, and no CD spinner I could find was able to match it, regardless of price. 
AP1.jpg Audiophilleo

Somewhere after the DDC craze hit its peak, something new crept its way in. USB filters, AKA regenerators or "decrapifiers". Take your pick. Notable examples include the Audioquest Jitterbug, the Uptone Regen, and the Wyred 4 Sound Recovery, among many others. These guys have similar goals as DDCs but with a different means to achieve it, and are often different from one example to the next... and their relatively low prices have really helped them take off. It remains to be seen how much this category will grow before being supplanted by something else.
Speaking of which, allow me to ramble for a moment.
This market is, like any other, prone to trends. The stuff people rave about today as their "end game" equipment is often gone from the system a few months down the line, replaced by the latest and greatest gizmo. We'd like to think this is due to advances in technology but if we're honest, a lot of it seems marketing driven. A "revolutionary" product today is old news tomorrow, superseded by newer and supposedly more refined versions. Between that, and the desire many people have to put that hot new product in their sig or profile, we end up with a steady churn of gear coming and going, each one supposedly more impressive than the last. I have mixed feelings about this state of affairs, but that's not really what this post is about. I just had to give you a feel for where I'm coming from before we went any further. 
Anyway, as I said, the Audiophilleo combo served me well for several years. It was very highly regarded at first, and still is in many circles, but as time went on I saw more and more forum discussion about how this or that DDC was superior. In my view the Audiophilleo had become an easy target, much like an HD800 which just begs for a comparison with every new flagship headphone release. Newer and potentially more obscure is always better in the eyes of some people. Which is fine - I don't care what others like or don't like, but for me the AP1/PurePower remained a reference component, even when faced with some tough competition like the Empirical Offramp 5 and Bel Canto RefLink. 
Meanwhile, at least on HeadFi, things progressed until general consensus said I could spend a few hundred dollars on one of several different DDCs and get vastly better results than the $1400+ Audiophilleo setup. Still very pleased with my reference, I figured it was time to investigate these things for myself. So I grabbed a Gustard U12, a few variations of the Breeze Audio device, a Melodious MX-U8, and a Yellowtec PUC2 Lite, hoping I could find this supposedly easy improvement. 
Long story short - I did not find any of these on the same level as the AP1/PP. After a thorough and frankly not very enjoyable period of testing, using everything from a modest Yulong D200 to expensive Esoteric D-07x and Calyx Femto DACs... I just didn't hear it. The AP combo was more open, more detailed, and generally more lifelike than any of the newcomers. I'll admit the Yellowtec is fairly nice for the price - better than my old Stello U3, and probably on par with my more expensive Resonessence Concero HD (which doubles as a killer DDC). And the other models from Gustard etc are nicely built for the cost. But as far as finding a new reference.... it just didn't happen for me. No offense to anyone who feels differently, but I was at the point of giving up on all this talk of major advances in DDCs, being happy to stick with my AP setup indefinitely. 
At that point someone I trust recommended a new device called the Singxer SU-1. I had never heard of it. Based on my initial reading, it looked like the brand hangs their hat on the latest XMOS chipset which is vastly improved from the previous gen in terms of processing power. The SU-1 was not quite released yet, but its little brother the F-1 had just come out and was causing quite a stir. So, without high hopes, I figured I would give this DDC thing one last try before moving on. And I'm glad I did.
The SU-1 arrived several weeks later. I got an early unit and it sounds like the company is having trouble keeping up with demand, or at least they were for a moment there. The SU-1 has a lot in common with the Melodious MX-U8 - both are roughly the same size and well built if somewhat industrial in appearance. I actually suspect the two were made by the same people (can't prove it though). As much as I like the Audiophilleo concept, I have to admit these DDCs with the more traditional form factor are much simpler to integrate into my audio system. The Audiophilleo eliminates and extra cable with its direct connect design but then adds several more cables to link up with the PurePower, so it still ends up being something of a mess. Meanwhile the Singxer sits neatly on my rack without drawing attention or complicating things, which I appreciate.
Front panel is simple - just LEDs for power, signal, and DSD, and that's it. Nothing fancy. Around back is another story though.... this little box has extensive connectivity. There's a standard IEC power input with a switch that you'll want to leave on all the time for best results. There's the necessary USB input, and then a whole bunch of other stuff - likely more than most folks will need. We get SPDIF outputs in both coaxial and BNC formats. We also get an AES/EBU output - which is nice, as I feel this format has potential. Many DACs have this type of input yet not many transports or players seem to use it any longer. 
Then there's an HDMI shaped output labelled I2S - I haven't used it much myself, but the factory says it works with DACs from PS Audio, Gustard, Audio GD, and Wyred 4 Sound, among others. I2S outputs have been around for a while and taken many different formats for transmission, so it's nice to see things move toward semi-standardization. I say "semi" because there remain a minor few differences between the inputs on those brands. Singxer provides options via internal jumpers on their smaller F-1 product, in order to feed the expected signal to each brand of DAC. I didn't see those on the SU-1 board and wondered if that feature was left out for some reason, until I happened to flip the device upside down for some reason.... there, mounted on bottom of the enclosure, are externally adjustable DIP switches, making the SU-1 that much more user friendly. I briefly tried mine (with the default DIP settings) on a friend's PS Audio DirectStream and it worked fine. Whether or not the I2S format has sonic merit over the alternatives is another matter but I'm glad to have the option. Lastly, there's a "Word Clock" output using BNC format - I can't find any info about it anywhere (Singxer is not big on documentation at this point) so I'll just ignore it for now.

Inside, the SU-1 can be broken down into two sections. First, the linear power supply with a shielded Talema transformer and multi-stage LDO voltage regulation. This PSU sits on its own PCB separate from the rest of the device, which is smart design in my book. The Gustard and Breeze Audio units had zero separation. The Melodious at least had the transformer on a different PCB but not the rest of the power components. 

Singxer's remaining board is a 4-layer PCB with lots of good things to offer. A pair of Crystek CCHD-575 "femto" clocks handle timing, while two ISO7641 digital isolators provide galvanic isolation to keep noise separated. A custom Xilinx FPGA works its magic doing who-knows-what to help the signal stay clean and uncompromised. Honestly I don't really care to endlessly discuss all the FPGA ins and outs (ahem - Chord Hugo) as long as the thing does its job and sounds great.
Singxer-3264.jpg The Latest XMOS Chip
Singxer-3267.jpg Galvanic Isolation
Singxer-3271.jpg "Femto" Clocks

Now, enough tech stuff. How well does this thing work? Does it improve upon the better options I've heard from Audiophilleo and Empirical and Bel Canto, all of which happen to be on the more expensive side compared to this new batch of supposed giant killers? 
The Sound
The answer is yes - surprisingly, this $399 device actually delivers what so many before had failed. Compared to my AP1/PP, the SU-1 brings improved spatial cues, superior micro-detail, and a slightly more "black" background, all while sounding more natural in the high frequency range. I wound't call it a night and day difference but with the right system, doing critical listening with excellent recordings, it's large enough to notice on a consistent basis. 
I didn't hear any downsides either. The Empirical Offramp 5 was very good but consistently seemed darker than the AP1/PP, to the point where it didn't work for my tastes unless I built a system specifically around that signature. The Singxer imparts no flavoring of its own, instead letting the DAC stretch its legs to the best of its ability without being influenced. I REALLY like this thing. 
The Singxer brought at least a small improvement to almost every DAC I tried. Interestingly, there was no real correlation between price and potential performance improvement. The Yulong D200 at $699 shows a very modest gain, while my Calyx Femto which sells for roughly 10 times as much gives a comparatively massive improvement - it's almost like listening to a whole new DAC. The obvious answer is that an expensive DAC should be more resolving and thus better able to showcase a superior source. But I'm not convinced that's all there is to it... looking at the USB design on the Calyx as well as my Esoteric D-07x ($5K) tells me even higher end devices don't always have the best USB implementations. The little D200 has a nice Amanero USB board running off internal linear power, and it works well enough to where the Singxer can't do a whole lot better - it's already bumping up against the limits of the DAC. My reference DAC is the new Resonessence Labs Invicta Mirus Pro which arguably showed no improvement at all, while my next best performer, the B.M.C. UltraDAC, showed a small but reasonably worthwhile gain - the sound was certainly different if not completely better. Meanwhile, huge, almost transformative gains took place in Simaudio's 430HAD, which is technically a headphone amp with a surprisingly nice add-on DAC. I like it well enough using the built-in USB input but it really opens up with the SU-1 in place. The Cayin iDAC-6 shows a fairly small difference while the Anedio D2 sounds absolutely killer with the Singxer, FAR better than the stock USB input. And the Unique Melody Platform Pure 6 was completely transformed into a world class system despite all its quirks - over standard USB it just doesn't come close to this level. I won't go on and on about each individual DAC other than to say A) the results were often surprising, and B) $399 was definitely worth it in the majority of cases.
Singxer-1-3.jpg B.M.C. UltraDAC
Singxer-3222.jpg Unique Melody Platform Pure 6 System
Invicta Mirus Pro, Cayin HA-1A MK2, HE-1000
Simaudio 430HAD, Enigmacoustics Dharma
Anedio D2, Pass Labs HPA-1, HA-1A MK2, HD800, K812
Cayin iDAC-6, iHA-6, HA-1A MK2

Overall, I was highly impressed with my results using this thing, but I figured perhaps there might be other options to explore as well, just to give a more complete picture of where things stand regardless of price. So I rounded up a few heavy hitters in the segments for comparisons - the Berkeley Alpha USB, Audiobyte Hydra Z, and a Soulution 590. Does throwing more money around make for an easy solution (no pun intended)?
Long story short, I think the Singxer is very competitive even in this expensive field. The Soulution is pretty respectable, but still inferior to my Audiophilleo setup, and thus overpriced for what it is. The Hydra Z is probably on par with the AP1/PP which is quite impressive to my ears - and I didn't even have their ZPM power supply which may have brought it up to another level. So I can definitely recommend the Hydra Z for the price they ask. But I was most impressed with the Berkeley - talk about a sweet sounding DDC! The Berkeley is everything one could want in a device like this, except.... it sells for nearly $2K and is highly focused on that AES/EBU output which not all DACs can accept. Still, I think most ears would concur with mine in thinking the Alpha is a stunning performer even at its relatively high price.
The Singxer, to my ears, is very competitive with the Alpha USB. I listened back and forth for quite some time, to the point where it became downright tedious, and still don't feel confident in judging which one is best. The conclusion I came to? If there is a difference, it's very small, and certainly not worth the extra cash you'll spend to get it. This is kind of a big deal since the Berkeley has been widely accepted as top dog for some time now. To get a similar, possibly identical level of performance for so much less money is almost hard to believe - but that's the way I hear it.
So far, so good right? The Singxer SU-1 is a killer value with superb sound quality. Should everyone rush to place their order? Not quite.  As with all other DDCs, it really depends on your DAC. The main problem as I see it is with the SPDIF implementation. All the fancy digital to digital conversion in the world won't do you much good when passed through a CS8416 DIR with its high intrinsic jitter. Which means some DACs just aren't good candidates for this type of improvement. Also, some DACs (the Anedio D2 for example) essentially have an internal DDC where all signals end up taking the same path, while others pass USB data directly to the DAC. Meaning potentially a shorter and more pure signal path compared to even the finest DDC. Do you know what your DAC does and what that translates to in terms of upgrade potential with a DDC? If not, you might want to find out before making a purchase. Granted a $399 device like the SU-1 is a smaller risk than a nearly $2K Alpha USB, but it's still good to be well informed before spending any amount of money.
We also have to consider your source - is the SU-1 being fed by a basic laptop which was never designed for high-end audio playback? If so, improvements can be substantial. If the source is a dedicated music device from a brand like Aurender or SOtM, there's a chance that direct USB connection might be the better choice, again depending on the DAC. Or you may just find the difference small enough not to bother with. It definitely requires some thought.
There's also the matter of DSD and really-high-res PCM. Most modern DACs can accept up to 384kHz PCM over USB. Yet they top out at 192kHz over SPDIF or AES/EBU - that's just a general limitation of those transmission formats. Do you have a small collection of DXD music? Too bad, can't play it over the Singxer. Same deal with DSD - most DACs accept DSD128 or higher over USB, while the Singxer can only support DSD64 - and even then it requires a DAC willing to accept DoP over SPDIF - Some do, some don't. I'm certainly not a format nut and don't care about missing DSD512 capabilities but I do have a decent handful of DSD128 albums which I can't play through the SU-1. So this is something to consider. Note that the I2S output has no such limitations, on the off chance you are using one of the few DACs which handles that type of signal. When I paired it with a DirectStream DAC it worked flawlessly, and would thus be my default choice unless I could find some SQ-related reason not to go that route.
Lastly, I'd suggest keeping all options in mind. For example, you might see better results using a USB device like the W4S Recovery or Uptone Regen rather than focusing on USB to SPDIF converters. I admit I'm not the target market USB decrapifiers since I usually run from a quality dedicated server or streamer. But I've done my share of comparisons and came out with the B.M.C. PureUSB1 being my favorite. The $390 PureUSB "restores, reshapes, and stabilizes" the signal prior to entering your DAC, and does an especially noteworthy job at turning mediocre computer sources into excellent transports. I found that certain DACs responded better to the PureUSB1 when the Singxer made smaller gains - B.M.C.'s own UltraDAC was preferable with the PureUSB1, as was the Cayin iDAC-6. My solution was to combine them, going from USB out to the PureUSB1, into the Singxer, then coaxial or AES/EBU out to my DAC. I don't think I necessarily heard much of a cumulative advantage, but neither was there any drawback compared to individual use, and this saved me the trouble of figuring out which one was best utilized in a given situation. Which one do I ultimately recommend? That's impossible to say without knowing your setup, and ultimately you could pick up both for less than half the price of a Soulution 590 or Berkeley Alpha USB.
B.M.C. PureUSB1 Active USB Regen Cable (all others are Cabledyne Silver Reference)

Still, if it sounds like I'm trying to talk you out of considering the killer device I just praised a few paragraphs above.... I'm not. I just want you to make an informed decision rather than get caught up in the hype of a shiny new toy. Yes, the Singxer SU-1 is potentially an excellent upgrade for some of you. In other cases, something like the B.M.C. PureUSB1 is the better upgrade. And for some, both of those devices together is an ideal combo. But let's not overlook the many others who just need to get better headphones, a different amp, etc. I regard DDCs and USB regen devices as being more efficacious than cable upgrades, but not nearly as important as having the right DAC or amp or headphones. Perhaps the best analogy would be power conditioners - in some cases they work wonders, while other times they don't do a thing in terms of audible enjoyment. The problem I see is when forum dwellers and yes, even reviewers (professional or otherwise) throw around absolutes - "buy this power conditioner and it will DEFINITELY improve your system. If you don't hear it, something else is amiss with your gear or your ears." That's not the right approach, and the same applies for DDC and USB regen devices as well. There are just so many factors at play that it's impossible to predict how much of an impact these things might have on your system.
In the end, the Singxer SU-1 stands tall among its peers, being the first DDC I found to clearly improve on my prior reference. That's a bold move for a $399 device, and a big win for those of us who enjoy stellar performance at a reasonable price. Let's put it another way - a less than scrupulous audio company could very easily pull a "Lexicon BD-30" using the Singxer SU-1 inside a fancy case. Add in some slick marketing and they could sell it for thousands of dollars.... and people would likely be happy with what they get for that money. Seriously, unless someone figured out the origin, there would be no indication of the thing being a $399 device in fancy clothing - it's that good.
We'll have to see about other upcoming devices using the same xCORE-200 series platform from XMOS. I suspect that despite the horsepower improvement of that chip, the results here still rely heavily on proprietary FPGA programming, those top-notch Crystek clocks, and good old fashioned design excellence. I don't necessarily expect a repeat performance from every newcomer, but we'll see. In the meantime, I'm off to listen to music for a few days without worrying about gear, in order to make up for all the tedious switching involved in this review. I think I've earned it.
T Bone
T Bone
Outstanding review!  Thanks for your hard work.  After reading your review I feel more confident about trying an SU-1. 
Superb review! Using SU-1 with Benchmark DAC-1 + special PC for audio (with audiophile usb card: PVD-Audio USB-AD) sounding very nice.

A few words about my SU1 that went for a tweak by ROSE Audio.
As you can see, the PSU is completely new and the tweak is quite huge.

Most important is the sound … and it rocks !
Black background is better, more refinement with better details, more “meat” and re-enforced organic character.
It’s really a step up.

Have a nice day !