project86
Headphoneus Supremus
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- Feb 21, 2007
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At this point, and on this forum, I don't think Yulong Audio needs much of an introduction by now. While mainstream audiophiledom may have no clue about the brand, HeadFi members know better. We've embraced several of their excellent offerings - especially the D100 DAC. With their latest D18 DAC – the most affordable DAC on the market featuring the ESS Sabre ES9018 chip - they've shown themselves capable of producing a true high-end product while still keeping the price relatively affordable.
Yulong now has a matching headphone amp to accompany the D18. Dubbed the Sabre A18, this amp is a beast. Class A, fully discrete circuit design, with XLR and single ended inputs and outputs. At $900 it certainly has some tough competition out there. Yet we know that Yulong always offers loads of value for the money with each of their offerings. Will that translate to the A18 being a reference quality amp? Read on to find out.
DESIGN
The A18 is a relatively small form factor amp. Its enclosure shares its size (but not construction) with the D100 and A100 units - 10" wide x 7" deep x just over 2" high. It weighs in at a fairly substantial 7 pounds. Like the D18, the enclosure is thicker and more "premium" overall compared to the D100/A100 models (which were already quite nice). It is available in silver or black - I chose mine in silver to match my D18.
Internally, there's a lot going on inside of this amp. Power supply features a Plitron toroidal transformer, large Elna smoothing capacitors, and a pair of LM337K linear regulators. Worth noting is that Yulong chose to use the TO-3 metal can package which allows for higher current than the standard TO-220 package. Each one is embedded in a rather substantial heatsink for maximum thermal efficiency in this high-current application.
As mentioned prior this is a totally discrete design. In the eyes of many, discrete designs will always be superior to opamps. Period. I’m not necessarily in agreement with that as a blanket statement - I’ve heard good and bad examples of both types, and each design has unique advantages and weaknesses. The trick is to design the circuit in such a way that those weaknesses are no longer a factor. Many of the prior Yulong designs use a combination of opamps and discrete output stages, so Yulong has experience with both.
There actually is a single opamp in the A18: an OPA2604 used to buffer the RCA input. This is similar to the Yulong A100 amp, and said to reduce dependence on signal source as well as interconnect cables. Aside from that everything is done fully discrete - K170/J74 JFET input stage, and MJE15030/31 low impedance output stage. Quality parts are used throughout the entire assembly, including Vishay BC series resistors and select Nichicon Muse capacitors. All connectors are from Neutrik and the volume pot is the popular RK27 "Blue Velvet" from Alps.
Yulong lists the specs for the A18 as follows:
SNR: >110dB
THD+N: 0.001%
Frequency Response: 20Hz to 20kHz 0.1dB
Output Power: 680 ohm 95mW, 300 ohm 200mW, 150 ohm 400mW, 32 ohm 1800mW
Power Consumption: <30W
Output Impedance: 2.2 ohms
Worth noting is the nearly 2 full watts per channel into lower impedance loads. That should certainly come in handy with planar headphones. But this amp has plenty of voltage swing for higher impedance headphones as well, dumping a peak 24V into 600 ohm loads like the Beyerdynamic T1. While it may not be quite as powerful as some of the recent monsters like the Schiit Lyr, rest assured that Yulong has designed this amp to handle nearly any headphone out there, with the possible exception of the HiFiMAN HE-6.
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EDIT: I'm adding a note here to clarify something that originally came across as confusing. This amp is NOT a "true balanced" design. I want to make that clear. Yulong explained to me: "We converted two negative signal wires together to achieve balanced output. This way customers who use a balanced headphones do not need to have an adapter but still can get very high quality playback sound." When asked another question unrelated to the balanced issue, he gave me this answer, which seems relevant: "It's not necessarily true that a single higher end part will deliver better sound in the final product. Design has to consider how all parts work together for the best possible final outcome. We suggest potential customers not to judge a product quality just by comparing single parts - product has to be evaluated as a complete unit, other than bits and bites." This would apply just as much to the question of "true balanced" design as it would to opamp selection or many other topics.
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Externally the A18 is very straightforward. The enclosure is 6mm thick aluminum, with venting on both sides. Both headphone jacks are of the locking variety. The only user interaction on the front panel is with the power button and the volume knob. A switch on the rear allows for selection of RCA or XLR input - I would have preferred this to be on the front panel even if it meant a slightly more complicated appearance. Another minor nitpick - the LED "ring" around the power button lights up green. This makes sense (green meaning "go") unless you stack the A18 with the matching D18 DAC, where the corresponding power LED is blue.
The A18 sells for $899. I got mine from official North American distributer Grant Fidelity, who offers great service (including 30-day in home trial). They also have a bundle with the D18/A18 combo for a discounted price – save $50 compared to buying them separately. Yulong likes to mention that buying from Grant Fidelity is the same pricing as if you flew to China and purchased the amp directly from a local shop – there is no dealer mark-up involved just because we are overseas.
PACKAGE
The A18 arrived quickly to my house in perfect condition. As usual with Yulong products, the protective styrofoam and box are adequate but not exciting. A user manual is included although it doesn't really have much to say.
BUILD QUALITY
The A18 looks and feels appropriate for what I expect a $900 amp to be. Connectors are all of high quality, the volume knob is heavy aluminum with a great feel to it, and panel gaps are suitably tight. While the design is not flashy it is obviously a step above the A100/D100. Some people complained about the D100 volume knob being made of plastic – the Sabre series gets heavy duty metal knobs that remind the user of their flagship status.
My unit has perfect channel balance even at low volumes. Being a pure Class A design, I do note a very small amount of background noise when I turn the volume nearly all the way up. This only shows up on a few headphones or when using sensitive IEMs. With headphones, it is never an issue because there's no way I could listen that loudly. With IEMs it can sometimes become problematic - this "Class A" hum will sometimes be heard in the quiet passages of some classical tracks. It doesn't ruin the experience altogether but I do think it makes for a somewhat less versatile amp overall. It's too bad because the amp otherwise pairs beautifully with all of my high end custom IEMs. One exception is my Earproof Atom dual driver custom - as a 70 ohm load, they are dead silent and sound really wonderful. I'll discuss more about that pairing later.
Another byproduct of the Class A operation is heat - the A18 can run quite warm. It's probably the warmest component I've owned in a while, though I haven't experienced the Schiit Asgard and its infamous sizzling temps. Like many other high quality Class A amps, the A18 couples its transistors to the chassis for heatsink duties, which helps explain why the whole thing warms up so easily. We don't have extreme weather in my area but I have run the A18 for several days straight in 80-something degree weather (though I'm sure it was cooler in the house) with no hiccups.
EQUIPMENT
This is the equipment I used during my evaluation of the A18:
Source: JF Digital HDM-03S music server, Marantz SA-1 (modified)
DAC: Yulong Sabre D18, Anedio D2, Violectric V800, Kao Audio UD2C-HP, Yulong D100 MKII, Grant Fidelity TubeDAC-11, Matrix Quattro DAC
Headphones: Audio Technica W1000x, Lawton Audio LA7000 lite, Unique Melody Merlin, HiFiMAN HE-400 and HE-500, Heir Audio 8.A and 6.A LE, Ultrasone Signature Pro, Earproof Atom, Thunderpants TP1, AKG K240DF, Sennheiser HD650
I let the A18 burn in for well over 100 hours prior to critical listening.
Power was handled by a CablePro Revelation conditioner and CablePro Reverie AC cables. Interconnects used were NuForce Focused Field RCA and Paillics Silver Net XLR. Some headphones had aftermarket cables: Toxic Cables Hybrid balanced and CablePro Earcandy single ended for HiFiMAN, Beat Audio Cronus, Heir Audio Magnus 1, and Toxic Cables Scorpion for custom IEMs.
LISTENING
My first serious listening with the A18 was done in the most obvious configuration: being fed by the matching Yulong Sabre D18 DAC via XLR cables and using the XLR jack with a balanced headphone. In this case I used the HiFiMAN HE-400 with a balanced Toxic Cables Hybrid cable. The result was nothing short of exceptional. It presented a big, bold sound with prolific low frequency extension, captivating midrange, and best of all - a very large and well defined soundstage. I had heard some great sound with the HE-400 from my other amps but I quickly decided that this was the best I had experienced from it. The black background rivaled the best I have ever heard, and the dynamics were astounding. Who would have thought that this was "only" a $399 pair of headphones? Switching to the HE-500 brought higher resolution, and more “snap” to the top end, though honestly I thought the HE-400 was so enjoyable that I may have preferred it overall.
As I cycled through the rest of my collection, I began to get a feel for the overall presentation of the A18. First and foremost, this is a warm and musical amp. It is not exactly "strictly neutral" and for that reason it will not be for everyone. No, this amp will appeal more to lovers of tube amps, lovers of vinyl, and lovers of "musicality" in general. Those looking for analytical perfection should probably look elsewhere. That's not to say that the A18 is majorly colored - because it's not. Let's be clear though - I expect any good ~$1K amp to sound pretty great all around. At this level we are talking about relatively minor differences in voicing. Also let me clear - not all of the ~$1K amps on the market are what I'd call "good" amps.
So far it sounds like I'm just presenting the A18 as some kind of brute - all brawn, no tact. Let me reassure you that the A18 can do subtlety, nuance, and delicacy just as well as it does power and authority. It was a joy to listen to Hiromi's latest album Voice and hear the subtle interplay between instruments. The same goes for complex electronic arrangements from the likes of Electronic Noise Controller, BT, or Marc Houle, and of course the usual jazz suspects like Mingus and Miles. So while the A18 does have a big, powerful sound, it doesn't come at the expense of precision.
I'll be more specific about the different aspects of the sound. Starting with the lows - the A18 has some serious drive to it. Bass reproduction is hard hitting yet remains very well controlled. It's the type of thing that raises the bar for other amps; you quickly get used to it, then expect it all the time. Switching back to an otherwise nice amp like the Matrix Quattro or Yulong's own A100, I was struck by the difference. The Matrix seemed a bit "one note" in comparison; a bit sloppy and undefined. The A100 comes close in terms of articulation but can't match the A18 in speed, texture, or most importantly - authority. Listening to these amps on an individual basis makes these shortcomings far less obvious. But when I use a headphone known for deep bass reproduction (LA7000, Thunderpants), and play the XRCD release Dancing With Drums (featuring some great Taiko action), I get a more convincing sense of depth and realism with the A18 than I do with almost any other amp.
Midrange on the A18 is what I'd call "seductive". It's the type of sound that could make a tube lover re-examine their preconceived notions regarding what a solid state design is capable of. The presentation is full and rich without veering into overly syrupy territory. I absolutely love vocals through this amp: Nancy Bryan, Livingston Taylor, The Persuasions, Jacintha... take your pick of "audiophile" quality music with really well done vocals, and prepare to be carried away. Lesser recordings tend to sound decent, but the highly natural sound of the A18 really begs for top quality material to showcase its abilities.
Highs on the A18 are really special - smooth yet articulate, extended yet controlled, airy but not bright. It's a study in seemingly contradictory behavior, yet somehow it just "works". This smoothness never left me wanting in terms of treble energy, though I know some people prefer a more "in your face" presentation. It is my opinion that a good number of people have conflated "brightness" with "detail", and thus won't accept an amp like this, however good sounding it may be, because it isn't pushing that "detail" down their throats. To each his own - obviously you have to go with what your ears prefer. But I maintain that this type of presentation is the more correct approach.
Soundstage presentation and imaging is yet another strength of this amp. Among all the headphone amps I've experienced, the A18 has to be near the top for this category, only surpassed by a select few competitors (all of which happen to be valve designs rather than solid state). It's an immersive experience that can really present a convincing soundscape, assuming the recording actually contains that information. This is impressive because it's usually the amps with heightened treble response that tend to give the perception of better imaging, as opposed to amps like this that fall more on the smooth side. But again the A18 strikes a great balance, and the soundstage is very dimensionally rich.
So far this sounds like I'm presenting the Yulong Sabre A18 as one of the best amps I've ever heard. And in many ways, it is. The main thing that holds it back just a tad is the fact that it exhibits a bit of background noise with sensitive headphones. This behavior was somewhat unpredictable - the Ultrasone Signature Pro, rated at 32 ohms and 98dB sensitivity, could pick up this hum/static with volume at roughly 75%. But the Lawton LA7000, theoretically more sensitive at 108dB and 25 ohms, could barely pick up any noise even with the volume wide open. The Audio Technica W1000x, a fairly sensitive headphone, was essentially silent, as were the planar models I used. Ultimately this was not an issue while listening to actual music at actual volume levels; but there's a chance that some other headphone which I didn't try would exhibit the noise in a way that would actually impact your listening.
Switching from full sized headphones and moving to custom IEMs, I find that most of them have this hum/static, but this time it actually does encroach on the music. Some are worse than others - my Lear LCM-2B, LiveWires Trips, and Westone AC2 are all fairly audible at medium to loud volumes. My Heir Audio 8.A and 1964 Ears 1964-T are less sensitive, consequently performing better in this case, and I can actually enjoy those for lots of music without being bothered. The exception is with music like classical which needs a bit more volume, thus bringing out the noise. My Earproof Atom, with its 70 ohm impedance, is dead silent with the A18 and sounds fantastic, but it is the exception rather than the rule. Ultimately I'd say this amp is not ideal for people who intend to use IEMs.
Just for grins, I tried to troubleshoot the problem by powering up the A18 without anything connected to it. I also tried different power outlets around the house, and various power conditioners from CablePro, Furman, and Panamax. None of these eliminated this noise, so I'm fairly confident it is just a byproduct of the Class A operation. But let's not overstate its significance - when used with full sized headphones, this amp is spectacular. And it certainly is not the only amp with this same limitation – many tube amps (even really nice ones) don’t play well with IEMs. The Schiit amps don’t, nor does the Matrix M-Stage with Class-A biased OPA627 opamp, nor does the Apex Butte, nor did the early versions of the Burson HA-160. Some of these fail with IEMs for different reasons, but the point remains – not every amp can shine with every type of headphone. If we stay away from IEMs though, the A18 really does a great job with pretty much every headphone under the sun. Some high-end solid state competitors (SPL Auditor and Phonitor for example) are excellent with high impedance cans but fall short with low impedance models. And most OTL tube amp designs are the same way. Other solid state amps are strong with low impedance models but only so-so with high impedance headphones. The A18 does a great job with both types.
COMPARISONS
The A18 is good enough to where it ranks up there with my best amps. There's really only one amp with which it begs to be compared: the Violectric V200.
The Violectric is a solid state powerhouse which is priced within $100 of the A18. It's been my favorite solid state amp for over a year now, and has displaced several more expensive competitors. Interestingly, the A18 and the V200 have more similarities than differences. They both present a deep, rich bass response with loads of detail and authority. They both have a somewhat smooth top end, though the A18 goes a little farther in that regard. Some people would call the V200 more detailed, while others would call the A18 more natural, so it depends on your perspective. The mids on the A18 are a little more "wet" sounding; richer, more inviting compared to the V200 being more straight forward. Again, it’s not a huge difference, but enough for me to notice. Perhaps the most important distinction in this comparison: The A18 does massive soundstage while the V200 is more restrained. Both have excellent image localization but the A18 presentation is just bigger in every dimension. This is one area where a few people were disappointed in the V200, so the A18 could be a great alternative for them. In its defense, the V200 has a completely silent background no matter what headphone or IEM is used, so it is more versatile in that aspect. It also has those helpful pre-gain adjustments, though it lacks the balanced headphone out option like the A18 has. As you can tell, I'm conflicted as to which model I prefer - they both have advantages in both usablility and sound, so it depends on the needs of the user. But the fact that the A18 keeps up with the V200 is impressive – the V200 is one of the best solid state amps around, for any price, and I ended up preferring it to the far more expensive Luxman P-1u.
There happen to be quite a few solid state designs coming soon in this price category. The Burson Soloist, the Schiit Mjolnir, the Cary Nighthawk, all promise high levels of performance, and all hang their hats on a discrete design. I may get the chance to try one or more of those in the near future, and I will update this review accordingly. I obviously can’t predict how that comparison will go – but I can say that I prefer the A18 to some existing products in the same price range. That includes the Burson HA-160, Musical Fidelity M1-HPA, and SPL Auditor. I don’t have those on hand at the moment for direct comparisons but I’ve spent a good amount of time with each and to my ears the A18 is at the top of that heap.
OPTIONS
I do need to mention about the different sounds you can get from the A18. Just like the D18 DAC, this unit has subtle variations in sound depending on which inputs and outputs are used. Yulong does give you the option of using the RCA inputs with XLR out, or vice versa. But doing either of these methods gives a somewhat rolled off top end which takes the experience down a notch in my opinion. I assume this type of operation passes through additional circuitry which takes away some of the transparency. In any case, if you must use XLR output but you don't have a source with XLR out, I suggest using RCA to XLR cables instead.
Sticking with XLR in and XLR out, or RCA in and 1/4" out, I do hear a subtle difference in flavor between the two choices. The 1/4" output seems slightly less warm, having a more linear presentation at the expense of some of the fun that makes the XLR out so engaging. Some people may actually prefer this sound - it's highly competant in its own right. Personally I like the character of the XLR out a little more. But the differences are not huge. When combined with the D18 DAC, which also has different flavors for each type of output, you do end up having two distinct sounds. The culmination of warmth from the XLR chain combines with the more three dimentional presentation to make for a very enjoyable listen. The RCA and 1/4" chain is more straight forward, more direct, more "hi-fi" sounding. It's nice to have both options available.
CONCLUSION
The Sabre A18 is very good - almost shockingly good in fact. Yulong intended this as a flagship offering, and it does seem worthy of that status. I've heard few headphone amps that play on this same level and all of those come with higher price tags. Anyone interested in a warm, smooth, yet highly detailed presentation that flows like real music should absolutely put the A18 on their short list.
Is it the absolute best amp for all headphones? Not quite. Its weakness is ultra-sensitive in ear monitors, which are not an ideal match due to subtle background noise. Aside from that it mates very well with every headphone I tried. I had worried that its warm, smooth tone may be too much of a good thing when paired with a darker headphone like the HE-400, but that that ended up not being the case at all – in fact, the HE-400 was one of my favorite matches despite being a relatively affordable headphone.
Ultimately I believe Yulong has done what he set out to do – prove that a small (but growing!) Chinese audiophile brand can keep up with the more well established players on the high-end headphone amp scene. Spending more than this does not guarantee a better headphone amp – I know this because I’ve done it. I doubt Yulong will ever become a mainstream brand, and they certainly won’t ever spend the same money on marketing as a competitor like Schiit. But in my mind their gear is very competitive and deserves to be heard.
EDIT
Kevin Gilmore, being the knowledgeable and helpful guy that he is, brought up the fact that this is not really a true balanced design. I confirmed with Yulong that it is a single ended design, which simply adds XLR as a convenience item. Kind of like the HiFiMAN EF6, among others. Apparently he was telling me this all along but it was lost in translation. It should be obvious just from the pics, but my mind has been elsewhere lately.
Does that make it inferior? Not really. Everything I said about the sound still applies. I feel bad for letting this slip by me though.
I just wish you had the Beyer T1 available for review purposes. I have been torn between the A18 and Mjolnir for quite some time, but had my doubts with this amp (lack of info, reviews and other well-established amps in this price range), so I jumped the gun and pre-ordered the Mjolnir (5yr warranty...hello!). For $750, with very similar, and better specs in every aspect compared to A18, it will be the "one to beat" on price/performance. Same with how the D18 is the one to beat in price/performance (especially since i bought mine for quite a bit less that's barely used). I'll be sure to keep your review as a reference to judge the Mjolnir as I may return it in favor of the A18 (not a fanboy). Thanks again.
