Pros: A transformer-coupled tube amp that can drive some lo-Z headphones for less than <$1000. Two slightly different sounding headphone outputs. Five output impedance settings. Sound can be dry, neutral, and detailed or warm, thick, and stereotypically ‘tubey’…but it sounds fantastic either way. And MOAR POWAH! Seriously...lots of power here.
Cons: Vertical form factor may not accommodate all desks/shelves. Lots of microphonics.
I’ve learned I have a thing for tubes. There’s just something about their euphonic sound – which can be thick and warm or neutral and detailed, but always euphonic. My tube journey started with a cheap Douk Audio tube buffer. Then, I had a Loxjie P20 for a brief stretch. That led me to pick up a Darkvoice 336SE and then start tube rolling. That eventually moved on to help fund a Monolith Liquid Platinum (MLP). Then, great deals came along for an Eddie Current ZDT Jr. and now a Cayin HA-1Amk2. Since the Cayin is still an in-production model, it gets a full review! This is that review! Now, fair warning, this is another long one. This amp has lots of cool features that all impact the sound. It took awhile to get a feel for everything which translates to having a lot to talk about! You’ve been warned…
I snagged the Cayin because a great deal on a used unit came along at a time when I was looking for a true tube amp – not a hybrid – that could come closer to the technical performance of my hybrid MLP or my solid-state Lake People G111 amps. Did I succeed? Read on to find out…
The Cayin HA-1Amk2 is an excellent headphone amplifier for the price. It’s a transformer-coupled tube amp that packs in a lot of cool features that are unique for a tube amp that lists for $999. The sound quality is very good for the price, it can match well with a wider range of headphone types than most sub-$1K tube amps, and the only real downsides of the unit are its physical size (for some) and its susceptibility to microphonics.
FEATURES & BUILD
It uses 5 vacuum tubes – one 12DT5 power regulation tube, two 12AU7 signal tubes, and two EL84 power tubes. My unit arrived with Cayin-labelled 12AU7, Electro-Harmonix EL84EH, and a Tung-Sol 12DT5 installed. The tubes are all housed internally in a quite large chassis. The top panel of the chassis is easy to open for tube rolling. I did not play with tube rolling for this review, because, geez, there’s a lot of other stuff to talk about.
It’s really large! That’s a chassis that measures 126.5mm×304mm×215mm or approximately 5”x12”x8.5”. The vertical orientation of the chassis gives it a chance to fit on some desks, but not mine. I had to build a pedestal for it under my desk.
Also, it’s heavy. It tips the scales at 9.5kg/21 pounds. However, the wood panels on the side are quite attractive, IMO, and the brushed aluminum faceplate is very nice. The porthole window in the front panel also shows off the glowing tubes inside. There are orange lights underneath the tubes giving them even more of an orange glow than the tubes’ heater elements would do on their own. Here's a pic looking in through that porthole window:
[Innards of a tube amp, or engine room of a starship from a Sci-Fi Movie?]
The overall build quality and construction is solid. But don’t throw it around, it’s still a tube amp.
There are 2 single-ended RCA stereo inputs labeled “CD” and “Aux.” One of the three knobs on the front panel switches between these two inputs. The back panel also has a preamp output. Special note here: there is no switch between headphone output(s) and preout. All are active simultaneously. I liked that feature until I was noticing lots of distortion in my 600Ω Beyerdynamic DT880. Turns out that driving headphones and a preamp output simultaneously – regardless of whether the power amp connected to the preout was powered on or not – taxed the Cayin’s amp. If you plan to use this amp as a preamp you should either not use 600Ω cans or manually plug and unplug the preamp output as needed. That I’m less a fan of because this thing sounded GREAT as a preamp for the Definitive Technology SM45 speakers I use on my desk.
The 1Amk2 has two 6.3mm (1/4”) headphone outputs, which are labeled “A” and “B”. Output A has a more active and energetic sound while output B has a softer, more laid-back sound. The difference isn’t huge but is noticeable. The outputs are also transformer-coupled and there’s a switch that adjusts output impedance to change the damping factor for headphones ranging from 8Ω to 600Ω. This switch has 5 settings: 8-32Ω, 33-64Ω, 65-150Ω, 151-300Ω, and 600Ω. What is damping factor? For amplifiers it’s the ratio of the load on the amplifier (impedance of wires and drivers combined) to the amp’s internal output impedance. This ratio is essentially a measure of how well the amp can stop the driver from moving. Presumably the higher the damping factor the quicker the amp can bring the drivers to a stop and thus the quicker/tighter the sound will be. With 2 headphone outputs with slightly different sounds and 5 output impedance settings, the 1Amk2 has LOTS of sound customization options.
The transformer-coupled output and the ability to drive headphones down to 8Ω is quite unique for a <$1K tube amp and also opens the door to driving low-impedance headphones and even some planar-magnetic headphones. I’ll discuss more details in a later section, but I had good success using the 1Amk2 to drive the Audeze LCD-2 (rev 1 prefazor), HiFiMan Arya, and Focal Elegia. I bought the amp thinking it would be great for my DT880 and HD6XX (it is!) and was very pleasantly surprised that it handled some of these lo-Z headphones so well. However, it’s not a guarantee. The Fostex 1.0T biodynamic drivers in my Lawton modded TH-X00 did not take to the Cayin well, nor did the easy-to-drive planar magnetic drivers in my HiFiMan Edition X V2.
The potentiometer is a high quality ALPS RK pot that turns smoothly and has no detectable channel imbalance. However, the knob that’s attached to it isn’t particularly large in diameter. That doesn’t bother me, but some may not love it.
This amp has some serious muscle. Cayin specifies the lowest output power of this amp to occur with a 64Ω load and even that’s a “meager” 850mW per channel. They claim 1.4Wpc at 32Ω, 1.2Wpc at 150Ω, and at 300 and 600Ω – where those Senns and Beyers we all love to tube hang out – they claim 2.0Wpc and 2.2Wpc, respectively. We can ballpark the voltage output – which is of more concern for those hi-Z dynamic drivers – by using the equation Power = ((Voltage)^2)/Resistance. That yields about 24.5V at 300Ω and about 36V at 600Ω. Plenty!
If the 1Amk2 has one true ‘weakness’ in the build it’s a tendency toward microphonics. With no music playing, tapping on the side or top panels can cause a sound in the headphones that sounds like a vibrating spring, or the sound of shaking an incandescent lightbulb. This same sound can also be heard while flipping the input selector switch or switching the output impedance. Microphonics are fairly common in tube amps, but this one seems to be well above average in the amount of microphonics it can produce. With music playing at any reasonable volume these sounds are not audible. However, if you have the amp sitting on a desk and you bump the desk it won’t take much to hear a microphonic sound. With my brick pedestal I don’t have an issue, but ymmv.
DACs used include Schiit Bifrost 2, Denafrips Ares II, and briefly a Holo Spring 2 Level 2. I mentioned some of the headphones earlier, but here’s a more complete list: Beyerdynamic DT880 600Ω, Massdrop + Sennheiser HD6XX, Focal Elegia, Audeze LCD-2 (rev 1, prefazor), and HiFiMan Arya. I also tried a Massdrop + Fostex TH-X00 with Lawton chambers and an HiFiMan Edition X V2, but those did not work so well. So, some care must be taken in matching the Cayin with headphones.
I have a definite preference for output A too – the more active/energetic one. My comments that follow are therefore based on primarily using that output.
May I confess I’m not entirely sure how to answer the sound signature question for this amp? It depends on what headphone it’s driving. The sound can range from something approximating but maybe not quite reaching dry and analytical all the way to that warm, thick, smooth sound that is stereotypical of “that tube sound.” I’ll get into more details on this with subsections for the different headphone types below.
There are some headphone-invariant sonic attributes, though. The treble is amazingly sparkly and detailed – much more than my previous tube-amp experiences had me prepared for – and I can’t remember, nor do I have written in a single note, that sibilance happened. I could crank my DT880 to levels that had me crying for mercy before I could get it to go too-sharp in the treble. Was it bright? Yes. Did I get lots of sharp esssssessssss and tttttt’s? Not that I can remember. I was floored by this. Cymbal crashes sound quite natural and effortless. The mids are also always buttery smooth with excellent timbre and detail. Voices sound wonderful. Instruments sound natural. Details like the echos of drums off studio walls are also resolved well. Bass is always well extended but its quantity and overall control seems to be the most variable aspect of the sound here. Spatial performance was also strong, with tight imaging, solid separation, and nice soundstage width. There’s also some decent representation of soundstage depth, too. The Cayin won’t challenge a $2000+ tube amp in spatial performance, but it seems strong for its price. Regardless of output impedance setting with hi-Z cans it sounds good, VERY good. With certain lo-Z cans and planars it also sounds VERY good. Overall, it’s an excellent sounding amp.
Sound With Different Headphone Types
Now because the sonic character can change so much due to which headphone is plugged in and output impedance setting, I’ll summarize some thoughts on how the 1Amk2 matches with each of the headphone types I used with it.
->High-Impedance Dynamics (HD6XX & DT880)
Yep, the HA-1AMK2 does exactly what’s expected here. It wakes up the bass and treble on the 6XX and brings up the bass a bit more on the DT880, it widens the soundstage, and brings out the delicious timbre each of these headphones has in their strength areas (mids for 6XX, highs for DT880). The “3-blob” spatial presentation of the 6XX also become more laterally coherent. The 6XX also becomes quite bassy overall. It has good bass quantity that almost satisfies my inner basshead. It’s also well controlled and punchy. The DT880 can also hit and rumble when needed, though it’s not quite as bassy in quantity as the 6XX becomes here.
It’s also with these hi-Z dynamics that the output impedance selector switch makes the biggest positive difference, and at that more with the 6XX than the DT880. The amp sounds good with either headphone on any of the output impedance settings, but increasing the output impedance changes the overall character. On the lowest setting, the 1Amk2 sounds dry and more detail-forward. On the 300Ω setting for 6XX and the 600Ω setting for the DT880 both headphones sound smoother and more relaxed. The output impedance selection seems to vary the sound on a “dry-wet” scale of tubey-ness on hi-Z cans. The differences aren’t huge but they are present, with the 6XX having the larger magnitude difference. I did not find details lacking on the higher settings – I have no notes that I heard a subtle detail with the low setting that I missed on the high setting – but the details are more forward with the low settings. Why is this happening? The output impedance selection decreases the damping factor as the output impedance increases. Since the damping factor indicates how well the drivers are brought back to rest, a lower damping factor means less control over the drivers’ motion. On these hi-Z cans that translates to a smoother, more relaxed sound. This changing sonic character is also why I struggled to nail down a sound signature for the 1Amk2. Do you want a dry, detail-forward, fairly neutral tube amp? You can have it. Do you want a thicker, smoother, “gooeyer” tube sound? You can have it, all in one unit.
-> Low-Impedance Dynamics (Elegia, TH-X00)
Let’s get the ugly one out of the way first. The TH-X00 drivers in my Lawton headphones did not respond well the Cayin at any output impedance setting. This Lawton/Fostex/me-messing-around chimera are bass cannons – maybe 16” battleship-mounted guns – with a stupid amount of low end. But they got very sloppy and boomy in the low-end on the Cayin.
I was pleasantly surprised with the combination with Focal Elegia. I was clued into Focal + HA-1AMK2 potentially being a good combo by Andrew’s review of the Focal Elex . He shows a graph where the Elex gets a natural bass boost from the Cayin. That was not my experience with Elegia; I noticed very little change in FR. Surprisingly, the bass was not boomy and bloated, either, as one might expect with a lo-Z can run on an amp with high output impedance. What I did find was the Cayin took a bit of the edge off of the Elegia’s attack. The Elegia can be an aggressive headphone, and it was more laid-back with the 1AMK2. That’s probably a damping factor deal again. Even on the low output impedance setting the output impedance is not below 1Ω like it is on most well-designed solid-state amps these days. The Elegia is specified as a 35Ω headphone but I found a couple of measurement sets here [https://reference-audio-analyzer.pro/en/user-report.php?id=1970#gsc.tab=0] and here [https://reference-audio-analyzer.pro/en/report/hp/focal-elegia.php#gsc.tab=0 ] that claim it averages more like 19.8Ω impedance. If true (and I don’t know these sites or how reliable they are, but having two of them makes me feel a little better), that suggests a somewhat low damping factor that would explain the smoothness. With low damping factor many dynamic headphones get very boomy and bloated in the 60Hz-120Hz range. Elegia did not do that with the Cayin. However, the Elegia’s bass becomes bloated and boomy when the Cayin’s output impedance selector switch is set to the higher settings. The Elegia still sounds rather detailed, but the soundstaging and imaging might take a small – very small – step back as compared to Elegia’s performance on the Lake People G111 amp. On the solid-state G111, the Elegia has all of its aggressiveness and tight imaging. The 1AMK2 makes it smoother and more mellow overall. Both versions of Elegia sound good so it’s all about preference here.
So that’s two lo-Z dynamic headphones with two different results. If your headphone collection is full of primarily lo-Z dynamic headphones you should be cautious about buying the Cayin. It may do nice things for some of them, and may do not-so-nice things for others.
-> Planar Magnetic Headphones (HiFiMan Edition X V2 & Arya, Audeze LCD-2 prefazor)
Starting with not-so-good again, the Edition X V2 (HexV2) didn’t necessarily sound bad on the 1Amk2, but it also didn’t sound good. It was dull and lifeless and lost a lot of the qualities that make it my current favorite headphone. The HexV2 can really slam in the bass when driven properly. It also has great midrange timbre, a huge soundstage, and sharp imaging. Of those, the timbre was about the only thing to survive with the 1Amk2. There was not a lot of bass, either in quantity or punch. The soundstage was still wide but also sounded flat.
I’ve had less time with it at the time of this writing, but I’ve enjoyed the Arya on the 1Amk2 so far. While it’s almost a next-of-kin to the HexV2, it drives very differently. I can’t go into super detail here but my initial impressions are the Arya’s bass extension and slam increase a little bit over the solid state options I currently have and may yet be just a hair more than my MLP can produce with it too. Detail and staging are also good. The overall sonic presentation is also that dryer, more detail-forward sound that the hi-Z dynamics had on the low output impedance settings too. I hope to flesh out these thoughts more when I get a chance to properly review the Arya, but as of this writing I’ve only had it in-house for a few days.
The LCD-2PF really rocks on the Cayin tube. I was very surprised how well those two jelled. It’s also a dry, detail-forward sound which pairs well with the smooth, relaxed LCD-2. The bass also extends well and has a decent amount of slam. There’s good detail and articulation to the bass as well. The bass quantity is just behind what the LCD-2 produces from the MLP as well, which isn’t crazy but also isn’t shy.
I have been asked a couple of times since I posted that I bought the Cayin in HiFi Guides forum: “can you use that with planars?” The answer is much like the answer with lo-Z dynamics: it depends. Of the three planar headphones I’ve tried, 2 produced good results and one didn’t. The one that didn’t (HexV2) is very easy to drive with a specified impedance of 25Ω and a high sensitivity of 103 dB/mW. The Arya isn’t necessarily high in impedance at 41Ω but has a rather low sensitivity of 91 dB/mW. Thus, the Arya will draw more current from the amp than the HexV2, which plays nicely into a transformer-coupled tube amp which will have to step down voltage and step up current to get to a lower output impedance. The LCD-2 has an impedance of 70Ω which is starting to get high enough that output impedance starts to become less of a concern. While it’s not a guarantee, planar headphones with impedance above 60Ω or with low sensitivity might have a reasonably good chance to sound good on the HA-1AMK2, but I would also advise making sure the Cayin is not the only amp you have on hand to power them, just in case. One last thought here: the output impedance selector switch does not do much to affect the sound of the planars that work well with the amp. Planar magnetic drivers are not nearly as affected by output impedance as dynamic drivers due to their near-constant impedance.
Do DACS Matter?
Well, DACs always matter. The 1Amk2 is resolving enough to let DAC character shine through, though. The warmth and thickness of the Bifrost 2 came through well and provided a good combo with the Cayin while driving hi-Z dynamics on low output impedance settings. That created a best-of-both-worlds type of situation for some material where the Cayin exerted lots of driver control and detail-forwardness but the BF2’s warmth came through a bit. The Ares II’s staging and energy came through as well. This pairing went the opposite way as BF2 + 1Amk2, balancing out the Cayin’s wetter sound from high output impedance settings with a higher perception of detail, while still having that great staging the Ares II provides. The Holo Spring 2 is just a higher tier of DAC altogether and I haven’t had much time with it, but suffice it to say that the Cayin does nothing to distract the fact that the Spring is a higher level of DAC.
Comparisons With Other Amps
The other tube amps I have experience with are the Darkvoice 336SE and Massdrop + Eddie Current ZDT Jr. The HA-1AMK2 easily outclasses both of those amps. The Cayin brings more power, punch, slam, and macrodynamics than the Darkvoice can muster and it brings more detail and superior spatial recreation than the ZDT Jr. can offer.
I also have been an MLP user for several months now and I’m currently running it with new old stock Amperex 6922 PQ Gold Pin tubes. With the hi-Z dynamic headphones I found the MLP to sit in the middle of the dry-wet spectrum between the Cayin’s sound on the low impedance and high impedance settings. Other technical aspects of the sound, like detail retrieval, spatial recreation, etc were very close. I found it often depended on the track as to whether I preferred MLP or the Cayin’s spatial recreation. I consistently enjoyed hard rock/metal with the Cayin + 6XX on the 300Ω setting. I also found the relative quantities of bass to vary by track, too. In some of my notes, while using the 6XX, I found the Cayin on lo-Z to have the least bass quantity, then the MLP, then the Cayin on hi-Z. On some other tracks my notes say the order was MLP > Cayin hi > Cayin lo. In any case, it’s not a huge difference, but is noticeable. The MLP also made the LCD-2 a bit warmer and smoother, where the Cayin dried out its sound and emphasized details a bit more. The MLP also had slightly more bass quantity with LCD-2. Both sounded good, and it was close enough that preference will carry the day here.
I like this Cayin HA-1AMK2 tube amp a lot – I mean I really like it. This review has been time consuming, with so many things to check out, and I still feel like there’s more to explore. But WOW has it been FUN. I’ve been grinning ear to ear playing with this thing. I bought it to have a tube amp that at least matched the MLP in overall technical performance and I succeeded. The ability to get a different but still enjoyable sound out of my LCD-2 and Elegia is very sweet icing on the cake. And I’ve never heard the 6XX sound so good before. I maybe didn’t gush enough above so I’ll do it here. The 6XX on this amp sounds wonderful. I loved that combo for hard rock and metal. I also love that I can crank my DT880 and not split my head open with the treble. Suffice it to say I’m super happy. This HA-1AMK2 will be my reference tube amp for awhile…probably until it makes sense to land a $2K+ tube amp. So, if you’ll excuse me, I have some tube-amped music to listen too…
Thanks once again for sticking out another long-winded review, all. I appreciate all your support. Enjoy the music!