xDuoo TA-20 Plus

It's been almost 12 years since I first started a thread "introducing" a company called xDuoo to HeadFi. At the time the company was focused on portable amp/DAC units, and their offerings seemed quite well sorted for that era. They had extensive functionality and very competitive sound for what I thought was fair pricing, and I enjoyed the time I spent with a few of their demo units. Since portable gear wasn't really a big focus of mine, I kind of lost track of what xDuoo might be up to from there, despite my enjoyment of their UA-05 device in particular.

All these years later, xDuoo is still around, and seems to have expanded its offerings to include both portable and desktop oriented devices. Their gear looks to be a mixture of both tube and solid state headphone amplifiers, dedicated DACs, and some integrated DAC/headphone amp combo units. xDuoo North American distributor Apos Audio was kind enough to send over an xDuoo TA-20 Plus which gives me a chance to see how things have evolved over the past decade. They also sent their Apos Ray 12AU7 tubes for some tube rolling action, so I'll have some thoughts on those later as well. I've been using the TA-20 Plus for a few months with a variety of headphones and source components, and have grown to really appreciate what it has to offer.


Design
The TA-20 Plus is a hybrid desktop headphone amplifier selling for $499. I'm assuming there was an original TA-20 model (before the Plus) but I'm not familiar with that at all, so I went into this with a totally clean slate (unless we count the units I heard a dozen years ago). xDuoo tells us the TA-20 Plus is a fully balanced hybrid design using a 5RZ4 tube for rectification, a pair of 12AU7 tubes for the gain stage, and a discrete class A buffer stage on the output. This should theoretically give a nice mixture of strengths - beautiful valve tone combined with solid-state technicalities, plus the ability to roll tubes to taste.

Of course, we've seen many hybrid headphone amps in the past, and some deliver on this promise more than others. The key distinction here may be the tube rectification, as that isn't so commonly seen in other hybrid designs. Or it may be the discrete (rather than opamp-based) output stage capable of delivering up to 2,600mW - enough to comfortably drive most headphones out there. Using the single-ended output lowers that number to 2,000mW which is still healthy enough to do justice to most headphones with just a select few (very difficult) outliers.



The company makes a point to note the size of the chassis whose profile is smaller than a standard A4 sized sheet of paper. Those desktop-friendly measurements conceal a fairly comprehensive feature set: two sets of RCA inputs plus a pair of balanced inputs in both XLR and 4.4mm formats (the latter handy for use with DAPs which increasingly feature 4.4mm balanced line-out connectivity). Outputs include the usual 1/4" unbalanced jack plus balanced connections by way of 4.4mm and 4-pin XLR. There's also an RCA line-out for aid in system integration, which would come in handy for those looking to work the TA-20 Plus into an existing speaker-based setup.

I really like the design of this amplifier, both from an aesthetic and a functional perspective. The left front panel is dominated by the previously mentioned trio of headphone outputs. In the middle of the panel is the (relatively large) VU meter, and I will never tire of watching that hypnotic dance as I do my listening. To the right of that is the volume display composed of 25 red LED "dots" per digit, which can show any volume level from 00 to 99. Next we get small indicators showing which input is currently active. Lastly, on the far right side we find the multi-function knob, which is tastefully done in red anodized aluminum to both match the red volume display as well as contrast the otherwise monotone dark gray of the device. Spinning the knob adjusts volume whilst pressing it cycles through the various inputs. It's all quite intuitive and I really can't think of anything I would want done differently.



Speaking of volume adjustment, that aspect is handled by the Texas Instruments PGA2311 digitally controlled analog volume chip, or more accurately a pair of them since this is a fully balanced design. That results in excellent matching between channels even at very low volume settings - avoiding the imbalance problems often seen in this price class when using traditional potentiometers. While the TA-20 Plus does not have multiple gain settings, the range seems large enough to accommodate everything from sensitive IEMs to power-hungry planars, as I'll discuss shortly.



Looks are obviously subjective but I personally find the TA-20 Plus quite fetching. The fit and finish are about as nicely done as anything I've seen in the sub-$1k price bracket, with tight tolerances and consistent finish indicative of a finely-tuned assembly process. The tube cage is effective and actually looks good (neither of which is always true with tube amps) and I actually leave it on much of the time. I was not sure how I'd like the dark gray color as it doesn't quite match with the black gear in my setup. But after living with it for some time I've grown fond of it - I'm reminded of my "silver" Pass Labs HPA-1 which is distinctly darker than my other silver gear yet somehow looks amazing when assembled together. The xDuoo amp has a similar effect when paired with my black equipment. Matching gear is great but sometimes a deliberate variation keeps things interesting without being over the top.




Listening
I plugged the xDuoo TA-20 Plus into various setups ranging from budget to modest to fairly extreme, just to get a sense of how it performed in different situations. I started with the stock tubes and later explored a few different upgrade options. As usual, listening was mainly done via Roon, and the gear was wired with Audio Art cabling all around. Balanced power was provided by an Equi=Core 1800 and a really wide range of headphones were used, the specifics of which I'll get into later.

In stock form, the TA-20 Plus gives a mostly neutral, universally pleasing sound that should have something to offer for almost any listener. I say "mostly" neutral as there is a bit of bloom and warmth, plus a very mild softening of treble energy as well as transient snap which collectively makes it a somewhat relaxed presentation overall. I would not call it overly dark though - there's ample response in the highest regions, it just doesn't have as much bite or sparkle as we might get from a truly neutral amplifier.

That slightly relaxed feel helps us focus on the crucial midrange presentation, which is beautifully done on the TA-20 Plus. Playing everything from audiophile classics (Pink Floyd, Fleetwood Mac, John Coltrane) to a variety of generalized rock (The Mother Hips, Murder By Death, Dengue Fever), highly technical metal (Carnosus, Beyond Creation, First Fragment), to other music I find harder to categorize (Zoe Keating, OK Goodnight, Nils Petter Molvaer), the xDuoo amp seems especially focused on midrange fullness, convincing vocal projection, a wide soundstage, and just a slight but welcome tube bloom. Low-end extension is deep enough to be convincing if not quite as authoritative as we might find in a top solid-state design priced in this same ballpark. It's a bit of a trade-off for that engaging midrange, and I'd say more often than not it's a worthwhile sacrifice.



The overall feeling brings to mind listening to a good single-driver speaker design, where midrange coherence, purity and natural tonality are prioritized over having the most extension up top and the most impact down below, as compared to a comparably priced 3-way multi-driver design. But again, this is not a massive coloration, more like a subtle bit of character that I notice after logging enough hours across different musical genres and headphones.

Note that pairing the TA-20 Plus with a somewhat lean sounding DAC is generally not a great idea in my experience. I don't think I'd personally choose a Benchmark or RME DAC (as great as those can be in other circumstances) as the result would not be as dynamically involved as I might like. This can be somewhat mitigated by tube rolling but even so, I think this amp pairs better with sources giving a somewhat meatier presentation with robust low-end impact.

The most synergistic pairing I found was probably the Musician Audio Aquarius DAC which is perhaps a bit much in terms of pricing compared to the xDuoo. But I imagine the more affordable Musician Audio Pegasus or even the Draco would also make great matches. One surprising combo that I ended up liking far more than expected was the Eversolo DMP-A6 streaming DAC. As a fairly neutral source, I would have theoretically placed it closer to the previously-mentioned Benchmark/RME camp in terms of perhaps not being an ideal match. Yet with the right choice of digital filter plus tube rolling (more on this later) the versatile Eversolo actually did a great job as long as we avoid certain headphones (HD800 for example). The DMP-A6 with the TA-20 Plus - along with some upgraded tubes - ends up costing roughly $1,500. While not an insubstantial sum, that seems like a pretty fair price for the level of SQ it delivers.



Headphones
When it comes to headphone pairings, I found quite a few that I enjoyed along with several that didn't seem ideal.

The Good
ZMF Atrium Closed: the 300 ohm ZMF designs always seem to thrive when driven by tube gear, and the TA-20 Plus is no different. Despite being a hybrid design, it still gives enough of that welcome liquidity and beautiful tube tone to make a great pairing. I particularly enjoy this combo with stuff like Pearl Jam, Hendrix, Soundgarden, The New Amsterdams, and other similar rock, due to the lovely way this combo renders guitars and vocals.

ZMF Caldera: I was unsure how this would go but the result is very enjoyable. It steers the sound away from the clinical side which can sometimes be the case with Caldera depending on the amplifier involved. This has just enough euphonic coloration to make it enjoyable for all sorts of music, whilst retaining strong technicalities. Listening to jazz or classical of all sorts? This might be my favorite combo of the bunch for those genres.

Audeze LCD-5: Similar to the Caldera, but even more accentuated. The LCD-5 has the potential to sound amazing but can also be very sterile, so system matching is key. The TA-20 Plus can be a great partner depending on source and tube choice. Stock tubes don't quite do it for me, but others move the needle in a pleasing direction with increased low-end impact and even more engaging midrange bloom. I realize this is something of an unlikely duo (based on pricing) but I just wanted to note that with the right tubes this combo is surprisingly enjoyable.

AKG K812: What a great pairing! I sometimes forget about the old K812, but using it with the TA-20 Plus reminds me of how good this thing still sounds. It's a great "monitor" style presentation that hits just the right combo of accuracy and resolution without going too far. The result is a punchy, fast, clean sound that feels accurate but not overbearing whilst sounding great with everything from Crooked Still to The Civil Wars to Chthonic. Anyone who loved the HD800/HD800S on a theoretical level, but couldn't bring themselves to actually enjoy those in the real world, would probably have a great time with this setup.

Focal Elex: Another superb pairing, with the added benefit of being much more price appropriate compared to the more expensive headphones listed above. This is just a great all around performer, suitable for all genres and pleasing whether listening at low or high levels. This was one of the few headphones where I spent time switching from single-ended to balanced output and while the differences were not drastic, I would recommend going balanced if you have the capability. It just seemed to give "more" of everything I enjoyed, from transient snap to soundstage width, with no downside other than potentially the cost of a balanced cable. I'd call it maybe a 10% increase in SQ, where single-ended listeners still get an enjoyable experience, but balanced is the best way to take full advantage of the amp.

Meze Liric 2: The Liric 2 is sort of marketed as a high end "portable" headphone but I just ignore that altogether and enjoy it at home. I haven't had it as long as the above headphones but so far it sits right up there with the Elex, Atrium Closed, and K812 in terms of being an attractive match for the TA-20 Plus. In fact I actually enjoy it more than its twice-as-expensive sibling, as I'll discuss shortly. Note that this one really does benefit significantly from balanced operation, and driving it single-ended seems rather flat and dull in comparison.

IEMs: I don't listen to IEMs as much lately but I did try some out and had fairly good results across the board. My AME Radioso was the best match, with inky black backgrounds and a saturated, punchy, and refined sound where the tube harmonics really shined through. The Ultimate Ears Reference Remastered was similarly excellent, with the focus shifted a bit towards speed and clarity. My 64 Audio A18t was also very enjoyable but did have a minor background hiss - not very intrusive, and actually quieter than the noise inherent in many older jazz recordings, but still noticeable at times. I suspect that would be more of a problem with certain other hiss-prone models like Empire Ears, but I didn't actually verify that yet. Still, the takeaway is that at least some IEMs do a great job here, despite that not being an expected strength for a fairly powerful tube-based desktop amplifier. Note that single-ended operation is totally acceptable here, with the percentage of improvement gained by going balanced ranging in the low single digits.


The Bad
Meze Elite: The Elite is one of my all time favorite headphones, but this combo just doesn't do it for me. It sounds a bit dull and dynamically compressed, lacking the full-bodied sound I know it is capable of delivering. There's no energy there, and the whole thing seems a bit "gray" for lack of a better word. Even with the ideal mix of source, tubes, and pads, the result topped out at merely "ok", which to my ears makes this something of a dead end. I'm not sure how many people would pair a $500 amplifier with $4k headphones, but as far as mismatched pricing goes, you'd be much better off with a Caldera or LCD-5.

Campfire Audio Cascade: This one actually didn't surprise me much. The Cascade is tons of fun but demands an iron-grip to control its fun but admittedly somewhat tubby low-end, and the TA-20 Plus isn't really up to the task. While I do think some aspects of the midrange presentation are great, the overall experience doesn't fit all that well.

Raal Requisite CA-1a: This is one of my new favorites and I'm still working on familiarizing myself with its character. It obviously requires the use of Raal's (included) TI-1b transformer box between the amplifier and headphone, and the specs indicate it needs at least 2 full watts minimum to perform well. The TA-20 Plus does meet that spec but feels like it needs a bit more juice to really make the ribbon drivers come alive. Either that or it's just not an ideal match in terms of sound signatures. It's certainly not the worst combo I've tried, but neither does go far enough in showcasing the capabilities of this unique headphone. I end up preferring the AKG K812 which gives a generally similar yet slightly better presentation, for a lower price, and without the complexity of the transformer box. Note that with the right amplification the CA-1a is a major step up from the K812 (as much as I still love that headphone) but the TA-20 Plus is just not the right match to make that happen.



Tubes
Apos also sent over their Ray 12AU7 tubes which sell for $180 for a matched pair. I'll do a separate writeup on those going into more detail, but the short version is that they pair extremely well with the TA-20 Plus, transforming it from a solid little amplifier to a borderline great one. The Ray tubes seem to unlock better articulation, more soundstage layering, and increased treble air over the stock tubes. The general nature doesn't change drastically but rather feels like an evolution, just being a more capable amplifier all around.

I've got some NOS 12AU7s that do certain things better than the Ray tubes, but that often comes at the expense of some other aspect. Not to mention the crazy pricing of NOS tubes these days. So no, the Ray tubes don't quite compete with my vintage Amperex Holland Bugle Boys, but that's expected considering the prices involved.

The stock tubes are not bad at all and I don't think people need to immediately upgrade in order to enjoy this amplifier. But down the road, I certainly think the Apos Rays are worth the expense for bringing the sound to another level without completely changing the overall presentation.


Comparisons
At the moment I tend to have a bunch of higher priced amplifiers on hand, so it's not really fair to directly compare most of them. I really wish I had the latest Schiit Lyr here as that seems like an intriguing competitor, but unfortunately I haven't heard that one yet. The best I can do are the following which are not terribly different from the TA-20 Plus in terms of pricing.

Musician Audio Andromeda: This solid-state amp sells for $869 which is less than $200 off from the TA-20 Plus if we factor in the Apos Ray tube upgrade. It offers a drastically different presentation, being very fast with extreme clarity and absolutely no bloom or coloration whatsoever. This gives a completely unique feeling when listening back to back with the xDuoo amp - Andromeda digs far deeper into the smallest details with laser-like precision, and is correspondingly ruthlessly revealing. Whether that's a good thing or a bad thing depends on your source/music/headphones.

Meanwhile the TA-20 Plus is much more accommodating and gives a relatively smoother, more laid back experience all around. While both models are fully balanced designs, the Andromeda takes a major hit when used via single-ended inputs or outputs. Meanwhile the xDuoo, while sounding its best in balanced mode, remains very enjoyable even when fed via RCA or using the 1/4" unbalanced headphone connection. The end result is the tube hybrid xDuoo being far less picky, focusing on musical enjoyment even at the cost of some accuracy, whilst the solid-state Andromeda is a more "serious" and demanding amplifier.

I can find situations where either amp is clearly superior, and there is not much overlap between them. This means folks would likely have no trouble choosing one amp over the other, though I can't predict which one that may be. Or, to look at it from another perspective - it would actually be quite useful to own both amplifiers, as they are vastly different to the point where each gives unique insight, and they could very happily coexist in a system.


Cayin HA-1A mk2: The Cayin has been around for a while by now so plenty of people have owned or auditioned it at some point. The original price was $999 but I see it go for significantly less on a fairly regular basis, to the point where it becomes generally cost competitive with the TA-20 Plus with the upgraded Apos Ray tubes. To contrast with the tube hybrid xDuoo design, this is what I'd call a more traditional transformer-coupled tube amplifier - although the aesthetic design is anything but traditional with its tall, boxy shape and rosewood enclosure.

In terms of sound the Cayin offers a more obvious tube bloom with excellent solidity and fluidity plus superior bass extension. But the xDuoo is more technically accomplished with a lower noise floor leading to superior dynamics and thus better compatibility with sensitive headphones or in-ear monitors. It also feels faster and more accurate overall, where the Cayin is somewhat obviously euphonic regardless of headphone choice.

Those differences can vary based on tube rolling which is another significant point of divergence. The TA-20 Plus gets moderately better or worse (or sometimes just different) when swapping tubes, but always retains largely the same core character. Contrast that with the HA-1A mk2 which completely transforms based on choice of tubes, to the point where it really does feel like a bit of a chameleon at times. There's definitely more potential inherent in the Cayin but of course extracting it can get rather pricey. If we focus on matching prices with a TA-20 Plus running the Apos Ray tubes compared to a (sale priced) HA-1A mk2 on stock tubes, I think I'd have a hard time not choosing the xDuoo for its cleaner and more linear presentation which still retains some great tube flavoring.


Conclusion
As stated above, I regret not having access to several more popular amplifiers in this price range, but I think my point stands - the TA-20 Plus competes nicely with two somewhat more expensive amps that I regard highly. The specifics of those comparisons may not matter as much as that general idea.

As for headphones, again the specifics may not matter quite as much as the overall numbers. I had great success with 6 different headphones and 3 CIEMs, whilst only 3 headphones didn't pair all that well for one reason or another. I consider that a very respectable ratio, particularly for a tube amp with a bit of character to it. I have a suspicion that if I were to incorporate more "sanely" priced headphones into the mix, the ratio would be even more favorable.

Ultimately the TA-20 Plus is an impressive amplifier which deserves attention for anyone shopping in this price range. I'm pleased to see xDuoo still around all these years after I first gave them a spotlight on this website, and I look forward to seeing/hearing what else they can come up with.