Anyone who is familiar with me or my posts on HeadFi probably already knows how much I enjoy the Yulong D100. I end up recommending it constantly both as a reference grade DAC and a very good all in one solution. Ever since I discovered the D100 I’ve been wondering what Yulong Audio would come up with next. Would it be a more budget oriented piece like their older products or something higher end along the lines of the D100? I was hoping that the D100 was not just a fluke, and that they were committed to producing similarly excellent gear from that point forward. When I saw that their new product was a matching amp for the D100 called the A100, I couldn’t resist trying it out. At $375 shipped, it still qualifies as a relatively affordable option, and faces some tough competition from such well regarded solid state amps as the Schiit Asgard and my personal favorite the Matrix M-Stage. Despite having what is in my opinion one of the most aesthetically striking designs around, I was curious as to how well it would stack up to this worthy competition.
My impression of the D100 was that the built in amp section was very good for the price. User Skylab reviewed the unit and came to a similar conclusion. His exact words were:
“Compared to the Meier Concerto, though, the D100 lacked some nuance, delicacy, and soundstage definition and air. But for the price, the D100’s headphone amp is quite good…”
This prompts me to question whether the A100 is even necessary for some users. Those seeking a compact all in one unit for a great price will likely be satisfied with the D100 alone, especially if they are using Grado or Audio Technica headphones, which in my experience mate very well with the D100. But to extract the maximum performance from the excellent D100 DAC section, a higher end external amp is in fact required. The A100 was seemingly designed to fit that exact role.
Once again I used the eBay seller wsz0304 just like I did last time with the D100. This seller ships quite fast and is highly recommended. In less than a week’s time my A100 had taken the long journey overseas and arrived to my house in excellent condition.
I’ll start with the description Yulong gives of the product. I’ve cleaned it up a bit to compensate for the slightly awkward language of the original, likely due to translation:
A100 is a class A transistor headphone amplifier, which is carefully designed: The power comes from a high quality custom made transformer with selected core material, then through a four-way regulating circuit, with the voltage and current amplification stages being powered separately. This is to ensure that the signal process is not interfered with due to power supply fluctuation. The input signal is buffered by an AD827 to reduce the dependence of the signal source as well as the interconnect cable. The low impedance signal from a buffer stage feeds into the volume control, and is then amplified by an OPA627BP (voltage amplification) and a class A transistor buffer constructed with BC557/567+MJE243/253 (current amplification). The output is separated 2 ways: one for high impedance headphones (direct output) and the other one for low impedance headphones (in serial with a 120Ohm resistor). The designer has been working for years to research the acoustic performance of different circuits, working parameters as well as components. Combining extended listening tests with analysis from dScope Series III digital audio analyzer, A100 has achieved excellent performance – not only in tests but also in listening sessions.
●Lightweight and durable aluminum housing design (Excellent match for the D100)
●Custom made, high quality toroidal transformer
●Hand matched transistors with digital transistor tester
●High end OPA627BP OPAMP
●Analog VU level display
●110-120V and 220-240V mains voltage (selectable on back plate)
●Input signal impedance convert and buffer
●Dual outputs to fit high and low impedance headphones.
A100 Technical Specifications:
680 ohm=75mw VPP=20V
300 ohm=170mw VPP=20V
50 ohm=343mw VPP=20V
33 ohm=1W VPP=17V
As you can see, the A100 uses a mixture of op amps with discrete amplification stages. In this way it brings to mind the HiFiMan EF5 amplifier. Where they differ is that the EF5 (as far as I understand it) uses a 12AU7 tube for voltage gain and then an OPA275 op ampwith a discrete component buffer for the output. The A100 (again, as I understand it) trades the tube for dual OPA627BP op amps (one for each channel) handling voltage gain, and relies on the class A discrete section alone for the output stage. For this reason it wouldn’t be completely accurate to call the A100 a fully discrete amplifier, but that’s a matter of semantics.
For some people op amps are seen as a deal breaker, and finding them used anywhere in a circuit is unacceptable. It may help to note that this is the BP variant of the TI OPA627 which is supposedly the best of the bunch, and commands the highest price of all active models in the OPA627 family.
The power supply appears nearly identical to the D100. Both employ relatively large toroidal transformers which look similar but are sourced from different manufacturers; the D100 from Plitron and the A100 from Ventronics. Like the D100 it has a built in switch for selecting 100-120V or 220-240V operation, so it works pretty much everywhere, and uses a standard detachable IEC power cable. All components inside appear to be of high quality, such as Wima, Panasonic, and Nichicon Muse.
The specs do not indicate how far this amp is biased into class A, or what the crossover point is where it switches to class AB. From a power perspective it seems to have a good amount of juice, although it is not an absolute powerhouse like some other designs. It delivers more power into lower impedance loads than high, and Grados or other 32ohm designs should be seeing over 1 full watt per channel. It does seem to do a very fine job even with 600ohm headphones. Some of the pictures I’ve seen showing the A100 in development appear to have a Beyer T1 being used for listening; I speculate that is a favorite of the designer and I have no doubt it makes a fine combination. What I’m not sure of is how well it would drive the new planar type models. It should have enough power to drive the LCD-2, and most of the HiFiMan models short of the HE-6. I need to get my hands on some of them to double check though.
Moving on to the outside, we see that the A100 is very similar in construction to the D100. It uses what appears to be the same chassis in general, with a few minor differences. That means it has the same dimensions as the D100: roughly 10 inch wide by 7 inches deep and 2 inches high. The front panel features a volume knob and dual headphone jacks, again just like the D100: one for low impedance headphones and one for high impedance models. The big difference is on the left hand side of the front panel. Where the D100 has a display showing sample rate and other info, the A100 instead features an analog VU level display for each channel. The top panel is also vented for improved heat dispersal. Overall I find the appearance very appealing, and it looks even better stacked on the D100.
The A100 arrived quickly to my house and in perfect condition. Packaging was not fancy but it did have plenty of protective Styrofoam specifically fitting the A100. Inside was nothing special at all: just the amp itself and the power cable. This is a simple product and doesn’t really need anything else, but this is one area where we can see an indication of the lower price.
The A100 is very nice looking. It features a thick brushed aluminum silver faceplate, and even though the rest of the unit is black, it has a nice textured smooth feel to it. The volume knob turns with tiny clicks that are felt but not heard, just like the D100. The rear panel RCA connections appear to be of high quality. On front, the analog VU meter gives the device a touch of personality. Despite their limited usefulness, I have always enjoyed the appearance of these types of VU meters; they remind me of classic McIntosh, Audio Research, and Accuphase designs.
Channel balance is just about perfect on my unit, even at very low volumes. There is no static, crackling, or other issues, just smooth clean volume adjustment. Some people may take issue with the “stepped” type volume control, but I found it very easy to work with. I never came to a point where I wanted to be at a volume level “in between” the steps. Like the D100, the background is completely silent. The only time I could get any sort of background noise was when running a sensitive IEM from the “high” output socket. That gave me a slight hiss and was way too loud for IEM use. Switching to the “low” socket IEMs became dead silent.
Given that this is billed as a class A design, I was unsure what to expect with regards to heat output. I’m happy to report that heat has not been an issue. The case gets somewhat warm but not what I’d call hot, even with extended high volume listening. I don’t know if that is an indicator that it isn’t extremely biased into class A, or simply a result of the large surface area of the case combined with the vented top panel doing a good job of dissipating heat.
Overall I can find no real issues to complain about. The unit is of high quality and has a nice weight to it, although the snobby audiophile in me wishes it weighed even more, because as we all know heavier gear equals better gear. But all joking aside, the A100 is a great looking and well built device.
I paired the A100 with the Yulong D100 for much of my testing. It’s just the natural choice as they were literally made for one another. But I made sure to try a bunch of other combos as well. Here is the list:
Dell Mini music server using FLAC files, fronted by a Squeezebox Touch
Hot Audio DAC Wow
Lawton Audio LA7000 lite
Sennheiser HD600 and HD800
Audio Technica W2002
1964 Ears 1964-T
Monster Turbine Pro Copper
I burned in the A100 for well over 100 hours, just to make sure it was in good working order.
These are just the impressions of one guy. I do these reviews for fun, not profit, and I don't claim to be any special authority. Many people have agreed with my assessments of other gear but some have also disagreed, and I totally respect that. We all hear differently on a physical level and we all have different preferences as well, so I think it almost impossible for one person’s impressions to apply to every other person. As with all my reviews, I hope you enjoy reading them and I hope they help our hobby to some extent, but I don't pretend that they are anything more than my opinion.
I’m going to be more direct than usual here, as once again I’m trying to make these reviews a bit shorter and more accessible. To cut to the chase, the A100 is a very solid performer. I know it can be hard to get excited about lower priced solid state amplification, but in this case I feel that something special has been achieved.
The general characteristics of the sound could be described as “crisp, clean, and controlled”. By that I mean that the amp is very neutral and transparent, not adding or subtracting anything from the signal. Across a dozen combinations of DACs and headphones, I could not come up with any apparent weakness, which is saying a lot at this price range. It doesn’t necessarily do everything perfectly, but is at least a solid 8 out of 10 in every category, and generally can only be surpassed by much more expensive gear.
It does not enhance bass in any way, and for that reason might not be the best match for some users. Personally I think there are cheaper options available for people wanting colored performance. That’s not what the A100 is about. Don’t get the impression that the lows are lacking or recessed though… far from it; the A100 controls bass and drives it with plenty of authority, never letting it get loose or flabby, and allows it to truly shine through without stepping on other frequencies. A specific example is called for: the AKG K702 has very polarizing bass performance. Some find it tight and well presented, others find it thin or lacking. Part of the problem is that the K702 is more difficult to properly drive than it would initially seem, and that last bit of refinement only comes with substantial amplification. The A100 does not enhance to K702 bass performance like some other amps do, especially tube amps. What it does is present it the way I feel it was really meant to be; deep, textured, and very refined, but without a ton of impact compared to some of the competitors from Sennheiser or Grado. The resulting sound is not unlike a high end mini-monitor in presentation, exhibiting a clarity and focus with certain music that is hard to match, but not being the last word in performance with other genres. The A100 gives the K702 some of the most accurate performance I’ve yet heard, and any shortcomings here are due to the headphone rather than the amp.
Mids are very involving and satisfying through the A100. Both male and female vocals come through as very realistic and three dimensional. Instruments (especially acoustic) are rendered with lifelike timbre and tonality, but not overstated or sweetened like some other amps will do. Once again, the A100 straddles the line between being musically accurate and just plain dry or boring. It doesn’t sugar coat the music at all but presents it with an honesty that can sometimes be brutal. You definitely want a nice transparent source to get the most out of the A100. With a poor source the accuracy of the A100 will only act as a magnifying glass and point out all the flaws. If only Yulong made a matching DAC that was equally transparent…
Highs on the A100 could be seen as one of the biggest strengths, or possibly biggest weaknesses, depending on perspective. What you have are such high levels of detail coming through that sibilance and harshness sometimes appear where you didn’t notice them before. This is not the A100 adding anything but rather the original source material being presented with more accuracy than you may be used to. This is of course assuming you have a detailed, neutral DAC feeding the A100. Using lesser DACs or disc players might not be such a good idea, but if someone was bent on pairing the A100 to a cheaper source I would recommend something that is smooth and relaxed in the highs. Better to roll off some of the content than accentuate a flaw. Even some higher end sources might not pair so well with the A100. Good but slightly treble oriented DACs like the Benchmark DAC1, PureAudio Lotus, and Musical fidelity A3 24 will probably not be the best match for the A100. But pair it with a somewhat neutral DAC and watch the grins appear. In this respect the A100 seems to be the DAC equivalent of a Unique Melody custom IEM; the highs are simultaneously detailed and extended but still smooth when at all possible.
Soundstage is well defined and fairly spacious. There is a stable placement of performers in their correct spots, and with the best recordings it can feel very lifelike. I hate using terms like “a row G perspective” but I concede that they can be useful; in this case I do feel that is an accurate description of the A100 presentation. It’s not up front and aggressive like my Vivid Technologies V1, nor is it laid back and slightly distant like my Maverick A1. Overall I’m pleased with it, but I recognize that this is one of those areas where spending big money will net the most significant improvement. As good as it is, the A100 doesn’t quite keep up with my Darkvoice 337SE or the Luxman P-1u. Those both cost significantly more, so I’m pleased with the performance of the A100.
The obvious comparison here is with the built in amp section on the Yulong D100. As mentioned earlier, the D100 amp is almost shockingly good considering the price and the fact that it is not the main feature of the device. If you are satisfied with it, stop reading this immediately and forget everything I just said. But if you find that there is still room for improvement, keep reading. The A100 adds a good amount of the nuance and soundstage definition that was missing, and tones up the extension at both frequency extremes. The improvement is almost hard to explain, and it can be relatively subtle with certain headphones. I’m not claiming a night and day difference across the board because that would negate everything I previously reported about the D100 amp. But the improvement clearly is there and it becomes especially noticeable when using certain headphones. For example: I would not bother to add the A100 when using a lower end Grado. Even my SR325 shows just a marginal improvement. But when I step up to my RS1 and especially my PS1000, things start to open up and become more readily apparent. I couldn’t detect much difference using the Fischer FA-003, but the HD600, HD800, and Beyer DT990/600 all showed modest but worthwhile gains in refinement and low frequency control. The biggest improvement by far was with the Lawton modified Denon D7000. I just got it so I have a lot more listening to do, but the A100 is so far my favorite amp to drive the 25 ohm beast. It sounds good with the D100 alone, but add the A100 and it becomes truly a world class performer.
In the end the question remains for D100 owners: should you add the A100? The answer really depends on your headphones and what you want out of your system. If you already have or plan on getting some high to very high end headphones, the A100 is pretty easy to recommend.
The other obvious comparison to be made is with the Matrix M-Stage. The Matrix is considered by many to be the reigning budget solid state headphone amp on the market. It is versatile and performs well with practically every headphone out there. It has 2 inputs rather than 1, and has 4 levels of gain adjustment which comes in handy. It also costs roughly $100 less than the A100. I was not sure how the comparison would go. But after spending lots of time going back and forth between them, I feel like I’ve got a handle on the differences. Both are still good amps and each actually has its own distinct flavor. Note that my M-Stage has not been modified in any way.
The M-Stage ends up coming across as slightly dark compared to the A100. It doesn’t sound recessed on top, but it also can’t match the clean extension of the A100. Bass on the M-Stage hits hard and fast and sometimes steals attention away from the rest of the spectrum. It’s a nice warm sound though, with lots of power behind it. The Yulong has more of an open, airy sound, likely due to the more linear treble performance. It almost makes the M-stage sound grainy by comparison. Bass performance initially seemed more subdued, but still very tight and perhaps even more extended. I realize now that the lows are not subdued at all, but rather the entire frequency response is wider and flatter.
So which one sounds better? Again, the answer depends. I’d say that the A100 is the more accurate presentation, and the M-Stage is a bit more forgiving. This translates to the A100 being better more often than not, while the M-Stage has a few specific instances of superiority. The main example is the HD800. I’ve always said that the M-Stage drives them about as good as any amp out there, and I still feel that way. With the A100, they end up sounding just a tad dry and clinical for my tastes. The K702 is also a strong point of the M-Stage, and sometimes I prefer what the pair has to offer. But for excellent recordings, especially classical, vocal, and some jazz, I prefer the K702 with the A100.
The differences between the M-Stage and the A100 remind me a lot of the differences between the older and newer models from Meier Audio. The A100 is very similar to the newer Corda Symphony and Concerto, while the slightly warmer and less detailed M-Stage is more equivalent to the old Opera and Cantate models. This is not necessarily a bad thing and really depends on the preferences of the listener. For me, I prefer the A100 more often than not, but my M-Stage still gets plenty of use. Note that while I have spent a decent amount of time with all 4 Corda models listed above, I don’t have any of them here at the moment, so I’m not claiming the A100 is the exact equivalent of the Concerto. From memory it is definitely in the same ballpark, but that’s as far as I’m willing to go.
Another aspect is the fact that the M-Stage has various upgrades available. Some people have gone all out with replacing capacitors and such, but the basic op amp upgrade is easily done, and can supposedly take the M-Stage pretty far. By reading descriptions of some of the available modifications, it sounds like people are able to make their M-Stages sound pretty similar to what I hear from the A100. I don’t believe the Yulong unit can be easily modified so that’s certainly something to think about.
Lastly, I find that the A100 pairs better with the matching Yulong D100, while the M-Stage pairs better with the Matrix Cube DAC. I don’t normally ascribe any special “synergy” to components just because they are from the same company, but in this case that’s just the way it pans out. You can pair them the other way but it doesn’t turn out as well. Still good, but not ideal.
The Yulong A100 is a simple but beautiful design. It doesn’t have crossfeed, independent channel adjustment, or even multiple inputs. What it does have is an elegant exterior, great build quality, and above all a superbly linear sound. It is musical, engaging, coherent, and free from any significant flaws. For owners of the D100 DAC, the A100 is simply a no brainer. You likely bought the D100 due to its clear and highly transparent sound, and the A100 provides similarly excellent performance, bringing amplification quality up to the level of the DAC secion. The duo comes in at roughly $850 shipped and is a very worthy contender at that price point. That combo plus a used Denon D7000 for around $600 make a good argument for ending the cycle of side-grades and upgrades and just enjoying the music, all at a relatively bargain price.
Despite the excellence of the combo, one need not own the D100 to enjoy the A100. It never failed to impress me provided I could supply it with a good clean source. Admittedly it isn’t the champion when paired with the HD800, but you can’t win them all. I do wonder what, if any, improvement could be gained if Yulong had decided to include balanced inputs/outputs on the device. I suspect that was omitted to keep the price low. This makes perfect sense except for the fact that balanced outputs are one of the highlights of the D100. Still, the performance of the A100 speaks for itself, and I don’t hesitate to recommend it in the sub $500 solid state amp category.
Edited by project86 - 3/26/11 at 9:07am