Yulong A28 Headphone Amplifier

Average User Rating:
  1. project86
    "Excellent performance from a balanced amp, without breaking the bank"
    Pros - Neutral with just a hint of warmth, plenty of resolution and grunt, powerful, good looks and build quality, not crazy expensive
    Cons - Needs a fully balanced system for best result, inconvenient rear panel switch for input selection, output impedance could be lower
    Around these parts, there's not much that needs to be said about Yulong Audio. Quite a few HeadFiers have experienced the neutral D100 series, the warmth of the A18 and D18 models, and of course the DA8 which is just a masterpiece in my opinion. Yet if you browse over to some other audio forums, you might find that Yulong remains virtually unknown. The brand is spreading, but nowhere are they as prominent as right here at HeadFi. Lucky us - Yulong makes some killer gear at reasonable prices.
    Under the microscope today is the latest headphone amplifier, dubbed A28. Yulong has a history of catering to headphone enthusiasts - all but a few of the prior designs have had some form of headphone amplification on board. What we haven't yet seen is a true balanced amp. Until now. 
    The flagship A18 remains the most expensive model in the Yulong lineup. It does feature a 3-pin XLR output but, like HiFiMAN's EF-6, the XLR is merely for convenience, making it easier to deal with headphones which already have that kind of termination. The internal designs are not truly balanced. Which, I might add, doesn't necessarily make either of those amps inferior. On the contrary: both are quite good in their own ways. Still, Yulong has several fully balanced DACs on the market now, so it made sense to release a matching headphone amp with a true balanced design.
    The A28 ($599) is clearly an extension of the DA8 DAC. They use a very similar enclosure available in silver or black, and even have the same unique footer system in place. The A28 stacks beautifully on top of the DA8 (or vice versa) but is a very close match to any other Yulong source gear as well. So feel free to drive it with a D100, D100 mkII, or D18, and you'll still have a nice looking stack, complete with balanced connectivity. 

    The rear is ultra-simple: IEC cable connection with voltage selection, RCA input, and XLR input. That's it. Like I said - simple! A small switch handles selection between the two inputs, which again is not the most convenient design in the world. We saw this on the A18 and I made the same complaint there. It wouldn't be so bad if the switch was off to the side in a more prominent spot, but in reality it sits squarely in between the RCA jacks. If you have RCA cables connected (and I assume that to be the case if you need to use the switch) then it is rather difficult to reach behind the enclosure and access. Especially if you have it in an audio rack like I do. The upside? It helps the front panel stay nice and organized. 

    The A28 can handle just about any connection you throw at it. There's a 4-pin XLR output as well as a pair of 3-pin XLR combo jacks. Each of these can accept a 1/4" jack - one labeled "high" (direct output, less than 10 ohm output impedance) and the other "low" (with resistor for protecting sensitive headphones, 100 ohm output impedance). This broad array of jacks means the A28 will work with pretty much any headphone out there, balanced or single-ended, though it won't be ideal in some cases due to impedance interactions.
    Power output is impressive: balanced mode gives 2500mW per channel into 32 ohm loads, 1300mW into 150 ohms, 700mW into 300 ohms, and 400mW into 600 ohms. Single ended operation gives roughly 1/3 those numbers, making it still reasonably powerful. Why more power in balanced mode? This is common for balanced amps, and I sometimes receive questions asking why this is the case. It's simple really - the device is based around a pair of OPA2604 opamps driving a "diamond" buffer constructed of MJE243/253 transistors. There are 16 transistors total in the A28 - 8 per channel when running balanced mode, or 4 per channel for each of the two single ended outputs. Using the "high" 1/4" jack, for example, actually uses just a single OPA2604 (which itself is a 2 channel opamp) and 8 transistors total. A friend could be using the "low" jack simultaneously, which makes use of the other half of the amp. Make sense? This is the reason why balanced amps such as this or the Firestone Audio Bobby or the Violectric V181 really demand to be used in balanced mode.... using SE mode just wastes a lot of their potential. Also note that when using the RCA inputs instead of XLR, an OPA1632 converts the signal to balanced. There is a small penalty paid here, but definitely not as significant as using just half of the amp via the SE output. So if you must deviate from a fully balanced setup, better to have a balanced headphone and a non-balanced source than the other way around. 

    Build quality is typical Yulong - see any of their other reviews for more on that, or just check out my pictures. Not much more to say on the topic. As always, North American customers are encouraged to purchase from Grant Fidelity. They offer excellent support both pre and post-sale, and were instrumental in translating my questions to the designer of this amp. Their price is on par or lower than the various (and potentially not authorized) sellers I see on eBay, so you might as well buy from a trusted source. 
    Since I'm a big fan of Yulong gear, I was able to pair the A28 with various products from the same family. I used their P18 power conditioner fed by their D230 AC cable as the basis for this system (all other cabling was Cabledyne Reference). For transports I used a YBA Design WM202 CD player, an Auraliti PK90 with NuForce LPS1 power supply, or later an Aurender X100L music server, with or without the Audiophilleo 1/PurePower. DACs were mostly Yulong - the D100 mkII, the D18, and the DA8 - but I also used the Questyle CAS192 and BMC PureDAC. For headphones, a wide variety of styles including HD800, HD650, T1, LCD-2, LCD-XC, TH-900, HE-500, HE-6, Alpha Dogs, Noble 4C and 8C, JH13FP, and ES5. All headphones have balanced cables - most using a 4-pin XLR but some with dual 3-pin style - with the exception of the T1 which is stock. I have single-ended cables for most headphones too, so I could switch them out to compare balanced performance versus SE.
    Dual 3-pin XLR from CablePro
    4-pin XLR from Toxic Cables
    Stock 1/4" cable from Audeze
    HE-6 and Thunderpants
    Way too much gear to list - I see TH-900, Alpha Dogs, HE-500, Spider Moonlight,Westone
    ES5, amps from Questyle and Auralic, and a Chord Hugo

    As you can see, I have a lot of gear to write about at the moment, so I was able to burn the A28 in for a long time before I got to it. I didn't bother to keep track, but it must have had several hundred hours (at least) before I gave it a serious listen. Burn-in believers, rest assured: that was not an issue here. 
    Yulong (the designer himself) is interesting because he doesn't always stick with the same "house sound". Look at his prior amp designs and you'll see the A100 on the more analytical side of the spectrum, and A18 on the opposing end with a smooth, musical presentation. The opportunity was there to make a generally neutral amp while still keeping the highly technical performance Yulong is known for. I'd say the A28 achieves just that.
    I'll cut right to that chase and say that if you intend to use this amp, you really should have a balanced system as your goal. Yes, it does have RCA inputs and single-ended outputs, and they don't sound terrible. But they also don't showcase the full capabilities of this amp. The RCA input is less of an offender - it's merely a small step down in performance compared to XLR. But still.... the best way to hear this amp is fully balanced from start to finish. 
    Having established that, I tended to stick with Yulong DACs to feed XLR outputs to the A28. The amp was very capable of revealing differences between the D100, the D18, and the DA8. I started with the D100 (mkII, since my original D100 is out on long term loan to a friend) and got very satisfying results. This combo was nimble and articulate, with a nicely defined soundstage and tight imaging. While not the most expansive thing I've ever heard, the accuracy more than made up for it. This was a tight, punchy sounding combo that had nice bass weight to the HD800 (balanced with Toxic Cables Scorpion cable) and yet didn't overdo it with the LCD-2 (stock balanced cable). I heard just the slightest bit of grain, which was only really noticeable in comparison to something like my AURALiC Taurus - which of course is much more expensive. It didn't have the highest resolution I'd ever heard but was nonetheless satisfying considering the investment for DAC and amp. Overall I'd say the A28 was more than capable of showing off everything the D100 had to offer.
    I then moved up to the more expensive D18. Now this was a whole new level of performance. As much as I enjoyed the D100, it was something of a lightweight compared to the rich, creamy presentation of its upscale sibling. Talk about open and spacious! The D18 remains one of the better DACs I've heard in that aspect, and the balanced A28 didn't hold it back one bit. I normally use the D18 with the matching A18 amp, so it was interesting to hear the difference with A28 in the mix. It was colder, but not cold in absolute terms. It was nearly as open sounding, with soundstage reigned in just a touch. Low frequency extension was similarly weighty but more dialed back compared to the A18, which is a rather warm amp compared to most. But the biggest difference came in terms of treble presentation: A28 had significantly more sparkle and air up top, while A18 was more rounded and smooth. Each presentation had its place - I preferred the A28 with my Alpha Dogs (stock balanced cable) and HE-400 (balanced with Toxic Cables Hybrid), while A18 was superior with HD800 and quite a bit better with the Beyer T1 (stock single-ended cable, which definitely caused a disadvantage to the A28). The A28 seemed to have a lower noisefloor, making it better with sensitive low impedance cans of all types. It's still not completely silent with IEMs - my Noble 8C (Toxic Cables Silver Poison balanced) was definitely listenable, and actually made for a better fit than with A18, but I still prefer it with other amps - the noisefloor is still not ideal, nor is the output impedance. And then there's the HE-6 - HiFiMAN's fussy flagship does a passable job with A18 but really comes alive with the A28 (again with the Toxic Cables Hybrid). I do love the creamy smoothness with A18, but the A28 just does a better job with more headroom, realistic air up top, and a more open sound. This is probably the most affordable amp I've yet heard that makes the HE-6 sound really good. This is also an extreme example of the single-ended discrepancy compared to balanced; the HE-6 does a complete 180 when used from the 1/4" jack, sounding thoroughly uninteresting and flat. Good thing HiFiMAN gives us a balanced cable right from the factory.
    Ascending the heights of Yulong's source offerings, I tried the DA8, and took yet another step up in performance. This time I heard all of the low end weighty goodness I had with D18, plus more airy treble and more speed. This was still no wispy, ethereal sounding system, and I'd call it slight tilted towards warmth.... but overall pretty neutral. I was really impressed by the upgrade compared to the integrated amp in the DA8 - which is already very high quality. The A28 is best via XLR, and the DA8 amp is 1/4" only, so the comparison is not completely fair. But in general the result was "similar yet better". Better extension on the top end. Definitely more sparkle and clarity. Richer midrange fullness, but not to the point of becoming overly thick. And bass extension? Yep, deeper and more authoritative. The A28 digs deeper into the recording to extract spacial cues and subtle details the DA8 amp can sometimes miss. But here's the thing - some headphones don't show much of a difference. For example, if I had some model from the AKG K7xx series, I'd rather just run it straight from the DA8. The A28 just doesn't add much in that case, and is definitely not worth the extra money. HiFiMAN's HE-400 is similar - the DA8 integrated amp already has plenty of power for that relatively sensitive planar, and the added cost to go balanced is somewhat prohibitive. However, with an LCD-2, or HE-500, or most Sennheisers, the difference is obvious and rather welcome. I'll reiterate what I said in my review of the DA8 - it has an excellent integrated amp section; one of the best I've heard. And yet, it can't keep pace with the A28 when used with some headphones. The DA8/A28 combo comes in at just a touch under $2k and I really think it's an amazing setup for that (relatively) down to earth price point. I've certainly heard my share of more expensive combos that didn't impress me anywhere near as much.
    I got good results by using non-Yulong DACs, despite the "stack" no longer matching. The A28 seems transparent enough to pass along whatever traits the DAC may have. So the Questyle CAS192 excelled at clarity and focus, while the BMC PureDAC was all about tonal accuracy. I can imagine a few instances where the A28 wouldn't make a good match with a particular source. The first, more obvious scenario - a DAC or CD player with no balanced outputs. Again, the RCA connection is not horrible by any means, yet it doesn't take full advantage of the amp. So running the A28 straight from the RCA outs of my YBA Design WM202, which I normally consider to be a great sounding CD player, sounded reasonably good but not amazing - no fault of the YBA. The other situation would be if the user needs a smoother amp to calm down the treble in their system. A brighter DAC, and a headphone like HD700 or Grado, would not make for a good system with the A28 in my opinion. In those cases, A18 is far more desirable. 
    Speaking of poor matches... some headphones just don't work very well here. Recall the output impedance is a bit under 10 ohms on the 1/4" jack labelled "high", and double that for either balanced output (4-pin XLR and dual 3-pin XLR are the same). So we can logically infer we need headphones under 80 ohms for SE mode or under 160 ohms for balanced. And remember, this only applies to dynamic drivers, as planar magnetic models don't care so much about output impedance. So what brands does that eliminate from our list of candidates? Grado. Audio Technica. Ultrasone. Sony. And probably a few more that I'm forgetting at the moment. Also most IEMs are off the table. What's left? Planars from Audeze, HiFiMAN, Fostex (including various mods such as Mr. Speakers), and soon Oppo. Most Sennheisers. Many beyerdynamic models. Is that enough for you? Is it wrong for an amp to be somewhat selective in its pairings, while being extremely good when a proper match is found? Only you can decide.
    The Yulong A28 is a brilliant amplifier when used in the right context. Unfortunately for them (but good for us!) it has some excellent competition in the same price range. A few years ago, this was not the case. In my recent experience there are three very good amps worth comparing to A28: The Lake People G109 (in the $600-700 range based on options), the NuForce HAP-100 ($595), and the Firestone Audio Bobby (MSRP is higher but often discounted to $500-600). 
    Picking a winner in this field isn't so easy. No single amp takes the lead in every category. Specifically, they each have their own unique focus in both sound signature and headphone pairing. So we need to break it down a little to find which works best for a given situation.
    The Yulong and Firestone are fully balanced, and sound best when used that way. The Lake People and NuForce are single ended only, though the former can be had with XLR inputs for a few extra bucks. So based on system matching (or planning for the future) you might eliminate half the field based on the balanced aspect alone. 
    To briefly compare the strengths and character of each amp: 
    The Firestone Bobby is similar to the Yulong in a lot of ways. It uses quad OPA604 opamps (which is the mono version of the OPA2604 using by Yulong) driving a transistor buffer. It has similar output impedance, and using SE mode will only engage half the amp. In direct comparison (balanced of course), the Yulong is slightly warmer, while the Bobby has a leaner, more airy presentation. Both have great soundstage but the Bobby edges out the A28 by a hair. In exchange, the A28 has more authority in terms of low-end impact. In the end, it breaks down as follows - both models are very good with planar models, but A28 is better, and is the only one capable of handling the HE-6 (have I mentioned it does quite well with that model?). Both models are also very good with the Sennheiser HD600/650 as well as the HD800, with the Firestone being a little better overall (especially with HD800, which seems counter-intuitive based on signature, but it just works). Neither model is ideal with IEMs or low impedance dynamic headphones. Personally, the A28 works for me with the headphones I happen to use more often, and the slightly warmer tilt is welcome more often than not. Your preferences could just as easily go the other direction though.
    Compared to the NuForce HAP-100, the Yulong is more resolving and hits harder, but has a less "exciting" sound. HAP-100 seems to emphasize midbass and upper mids, in a sort of smiley-face fun EQ situation. When it works, it works marvelously - look no further than HD800 for proof of that fact. The HAP-100 pairs spectacularly well with that particular headphone. It's not necessarily the most neutral you'll ever hear the HD800 sound - maybe it was never intended to sound like this the first place. Regardless, it's really enjoyable. The NuForce also works nicely for the lower impedance dynamic models like Audio Technica and Denon. The A28 won't do those so well, but is easily superior with planar models, where the NuForce is merely "capable" at best. So, again, both models have their specialties, and your preferences will determine which is the best match for you.
    Lastly, the Lake People G109. I actually have the G109P with the XLR inputs, which allows me to properly compare them using the same exact outputs from my DAC. The Lake People is very similar to the more expensive Violectric V100 (though not an exact match) but using a less fancy enclosure to keep costs down. It has the distinction in this field of being absolutely compatible with every headphone out there, from sensitive IEMs to the HE-6 and everything in between. It does use an internal jumper for gain adjustment, which is less convenient than the external switches on the Violectric models. I tend to leave mine on a low setting because it works well with most headphones, but if I was using it as a dedicated HE-6 amp I'd go for a higher gain. Still, it's far more versatile than any of these other three amps. Output impedance is less than 1 ohm so no impedance related issues. The G109 is a universally good performer and an easy recommendation for someone who hasn't settled on their favorite headphones yet. Having said that - the A28 seems to perform better in certain instances. I can't say if this is due to the balanced aspect, or just the sound signature. Both amps are very powerful and both do their best into lower impedance loads - G109 does 2300mW into 50 ohms, while A28 does 2500mW into 32 ohms. Which means both are ideal for planar magnetic headphones. In fact, these amps are more similar than different, and at times I had trouble telling them apart. I definitely prefer the G109P with IEMs and low impedance cans like the Fostex TH-900. I +think+ I prefer G109P with my HE-500. And I generally like it a bit more with my Sennheisers and beyerdynamic models. The rest of my planars - HE-400, HE-6, Alpha Dogs, LCD-XC, and LCD-2, seem a little better with the balanced A28. It tends to bring out more "bite" from the somewhat dark LCD-2 while at the same time avoiding edginess with the HE-6. It seems like we could generally call the G109 darker/more musical, and the A28 more neutral/higher resolution, but then they both go and defy those descriptions at times, with certain headphones. So I give up trying to characterize them any further and just put it like this: for me, these two are just about tied for my top recommendation in this space, with the NuForce and Firestone amps trailing behind (and roughly tied for second place). Which is an impressive achievement for Yulong given the high quality of this field.
    Other worthy competitors may exist, but I either haven't heard them or haven't spent enough time to really draw a useful conclusion. I definitely like the A28 more than the Schiit Lyr, based on what I've heard so far. I suppose some combination of tubes may exist that brings the Lyr up to another level, but I've not found it yet (and I've heard it with some rather pricey tubes). The Mjolnir is not one that I've heard enough times to decide on.... I sort of liked it, but then again I found it somewhat edgy and aggressive. It's very exciting for the short term but I'm not sure how long I would enjoy it. That's about all I can think of for the moment - I don't care for the Burson Soloist (any of them), nor do I find the Woo WA6 particularly amazing for the price as an all around performer (though it sure does sound nice with a few specific headphones). I could go on, but realistically I think the reader will know by now if the A28 might be their sort of amp - so I'll stop here. 
    Lots of words written above, and I'm sorry if this ended up as somewhat long-winded. That's the price we pay for having so many good options appear in this class within the last year or so. The quick and dirty version: Yulong has yet another exceptional performer in their stable, capable of matching the best in the category. Neutral with just a hint of warmth, the A28 sounds utterly ravishing when used with the right headphones. Downsides? Yep, there are a few, as expected for the price. Balanced inputs are recommended, balanced output is downright mandatory. And not every headphone will be a good match. If you can work within those parameters the A28 will reward you with some of the best performance available this side of a four figure price tag.