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Monaural amplifiers
Air Tight ATM-211

Price: 48 000 PLN with standard tubes, 49 900 PLN with KR Audio power tubes

Manufacturer: A&M Limited

4-35-1 Mishimae, Takatsuki-city, Osaka
569-0835, Japan
Tel./fax: 81-726-78-0064

WWW: Air Tight

Polish distributor: SoundClub
Country of origin: Japan

Text: Marek Dyba
Photographs: Marcin Olszewski, Air Tight

From time to time I hear from one of fellow audiophiles that they envy me because I have a chance to listen to so many different devices. But to be honest as every audiophile also I have my own preferences and that makes listening to some loudspeakers, amplifiers or players much more fun than to others. To be clear - it doesn't make the latter bad or not even worse devices! To really enjoy listening session I need particular system to sound not only very good but also the way I like it. Surely I can recognize the quality of reviewed items even if they don't sound exactly the way I would like them to – but I just don't wish I had them. It is also true that sometimes reviewer's job brings fantastic benefits when I receive devices way beyond what I could afford, offering sound that I simply love and I really, really wish I had them. It doesn't happen that often – I would say I reviewed 6 maybe 8 such items, that's it. Among those quite few there were already two devices by … AirTight which already made me a great fan of this brand. It all started with ATM-300 – the best 300B based SET I heard so far. There is also a PC-3 cartridge that created absolutely synergistic system with my deck and arm. Sooner or later I'll have one! Unless of course I find something even better which is quite unlikely because cartridge reviews are a real rarity. This time I received another SET from AirTight – based on famous 211 power tube.

To date we tested::


There are some Japanese companies that earned their status of „legendary” manufacturers with outstanding performance of their products. Nowadays this adjective lost most of its original meaning as it is used in regard to almost anything. But if you have a chance to spend some time with one of the Kondo, Shindo, Wavac or AirTight products you will realize that these are really special and these brands deserve to be called „legendary”. It looks like Kondo devices are not reviewed at all – I guess manufacturer and distributors don't think it is necessary (and they're probably right). Shindo is not distributed in our country at all – what a shame! Wavac's status on our market is somehow unclear – I was lucky and I had a chance to review a 300B amplifier opening their range (a very good amp I must say) but that was it. And last but not least – AirTight – the only one of this „Big Four” that not only is distributed in Poland but the range of products available for customers and reviewers is slowly but surely growing. That is how I became a great fan of this brand and I know I'm not the only one.

The ATM-211's external design is somehow characteristic for AirTight products – dark gray casing (dark gray might not sound very attractive but believe me – it is damn nice), black (very dark blue in some light) huge transformers cups, individual pots for each channel (ATM-300 has these too, even though it is a single amp not monos), small gold-ish plate with logo – all that creates an image of something very special. When you take a first look you can't take your eyes from huge 211 tube that is placed in nicely finished socket. The top panel of each amp is mostly occupied by three huge transformer cups, so in fact there is very few place left there – just for one huge 211 triode and a small, round bias meter (nicely finished in the same fashion as 211's socket). A front-panel switch, placed next to volume control pot, turns on the meter, which provides monitoring of power tube's bias voltage. The bias can be adjusted with a trim pot accessible through a hole in the top of the chassis. A 12AX7 (ECC83) and a 12BH7A comprise the rest of the tube complement. These are placed next to one of the transformers in the back left corner of the amp. Inputs are single-ended RCAs and the speaker terminals are made by WBT (these are single posts – the output transformer comes set for a nominal 8 ohm load, but can be factory-configured for 4 or 16 ohms, or reconfigured later by a Distributor on Customers request).

Even though some purist audiophiles might consider volume controls to be an additional, and though harmful element in signal's path but I don't think that guys in AirTight would have added this functionality had it really been harmful to sound quality. So since these are there all you need to create a full system is some source of signal and loudspeakers. Surely many of us (me included) have more then one source, but if you do and you want to use them all you need to either buy some fabulous preamplifier or get used to unplugging and plugging back interconnects from different sources. Having preamp in the system you won't have to use two pots for each channel separately and additional bonus of getting a preamp might be also a remote control. If you are a „sit down and stay there during whole listening session” kind of guy – you have to afford to buy top quality linestage (which won't be easy I guess – I mean finding something that at least won't spoil the sound of AT-211).

All right, let's get finally to the sound, shall we? During this test I used mostly analogue sources - Super Seven La Roccia with SME arm and Accuphase cartridge (see a separate review of this amazing piece of tech), and my own Gyro SE with amazing TransFi Tomahawk arm and Koetsu Black. The last element of this system were JAF Bassoon loudspeakers (used also for TRI review) – if you check the price you might think it was a cliché but you should remember that it is not the price that really decides the performance.

The first listening session happened at my friends. He (as a potential customer) was testing ATM-211 together with Ardento OB speakers (that you might have noticed during the last Audio Show). As a fan of „old school” loudspeakers I was amazed from the very first moment by the unbounded, natural bass (there was a 15' woofer plus 20 cm full range speaker mounted in each OB), organic midrange and treble and wonderfully palpable overall presentation. After a while I realized that some tweeter would be recommended as the top end wasn't open and sparkling enough – I obviously wasn't the first one who realized that, as there was already work in progress on a new project with additional ribbon driver. This might be a story to tell in another text as I truly hope to review this new model of Ardento OB. I still wanted to mention this listening session as we did an interesting comparison between my friend's own ATM-300 (AirTight's 300B SET) and ATM-211 using Ardento's high-efficiency speakers. After couple of hours with 211 we switched to 300B amp and … have I mentioned already that I was a 300B super-fan? After just two or three pieces I said that midrange and treble were much more natural and richer sounding when we used ATM-300. On the other hand more powerful monos (offering 22W instead of just 8W) handled big woofer with ease controlling it perfectly whereas 300B amp failed to do so. Arne Domnerus „Antiphone blues” was a perfect example – wonderful saxophone, church acoustics – there were amazingly well reproduced by ATM-300. But the other instrument – organ – sounded very weak and flat. It took the much bigger power of 211s to present this mighty instrument in a proper scale, with a proper power./p>

Use of one of those amps was very dependent on the repertoire. 300B was enough when we listened to some vocal recordings or to some jazz trios but to make a good use of huge woofer when it came to more dense recordings we had to use ATM-211. No doubt that more versatile partners for Ardento OBs were amps with 211 triode on board. For me this particular listening session was another proof of 300B superiority in some aspects of sound over any other triode, although it also reminded me again that different tubes might be superior in the other aspects and sometimes these other ones could be crucial for particular system. This particular match-up showed me that 211 could not offer as dense, crème, palpable midrange as 300B could. It wasn't also able to reproduce the ambiance, the acoustic environment of each recording as well as my favorite did but here the difference was not so distinct – maybe without head-to-head comparison I would not have been able to point it out. No doubts 211s had their advantages too - much better control of a bass range, better extension, it was more hefty, but also there was more precision in the whole sound, and the whole range was more flat. I think that ATM-211 would have presented same advantages even if we had used more efficient speakers – 300B isn't really capable of such a tight, full and so well differentiated bass and in general it focuses more on liquidity and richness rather then precision and speed. If I was to chose one single thing that amazed me most about 211s sound it would be something I could call immediacy of each attack – like each drums stick strike or a pluck of a bass string – it immediately delivers huge portion of energy, one can hear it and feel it when it happens and not shortly after that. Quality of treble is comparable (very good in both cases), although this ability of more accurate presentation of room's acoustics might be a small advantage of 300B triode.

That's quite a lot of word about quite a short listening session but I have to admit that both head-to-head competition between ATM-300 and ATM-211, and Ardento loudspeakers were really impressive. It not only sounded damn good but it sounded the way I liked it (which is not necessarily the same thing). It wasn't perfect, but the new version, a three-way OB might be. We'll see about that when they are ready.

Few hours and 60+ kg later ATM-211 landed in my room hooked to J-A-F Bassoon loudspeakers – also OB type although a different one. Their sensitivity reaches 90 dB, which is still too much for 300B SET amp. 211S had no problem at all driving those speakers and proved one more time how good speakers these were.

Let me start with something that never was too important to me, at least not until I reviewed Hansen Prince V2 and now Bassoons with ATM-211 – it's bass I mean here. What caught me by surprise was how incredibly fast and powerful bass was. The most accurate description here would be probably “immediacy”, and maybe also “uncancellable/consistent”. I realize you might now have no idea what I mean so let me try to explain – it is not uncommon that when reproducing some music some elements are left unfinished. An example – when a stick hits a drum it causes in fact some sequence of events – to simplify it let's just use three stages: the hit itself, then membrane yields under this strike and it gets back to its original state (action and reaction). So what I meant when saying that often such a process was left unfinished was that I could hear only the first stage – the strike and that was it, nothing more. AirTight delivers it all – it is very consequent about it, it's uncancellable, inevitable – if there is stage one there must be also stage two and three! Quite a few amps I heard so far could do the same. Since I listened Bassoon with Modwright KWA100 SE before I knew that the above described effect comes partly from speakers themselves due to their design that significantly reduces interaction with room's acoustics (it mostly concerns bass range) which allows to perceive specially this range in a different way than with other speakers.

But only when driven by ATM-211 Bassoon showed their peak performance which lead to a conclusion that significant part of credit goes to Japanese amplifier. What surely contributed (from amps side) were huge, oversize transformers providing enough power to drives each driver with absolute control.

The fact is that in each and every good drums recording stick striking a drum sounded incredibly realistic, authentic. Perhaps Prince could deliver more weight of such strike, moved more air in the room but even though they were driven by Tenor amplifier (even more expensive than these fantastic speakers) there was no such “immediacy” that I noticed here and I couldn't then “see” how the membrane of a drum reacts to the strike. It is really hard to describe or explain – I'm doing my best but I imagine that it might still not be enough for (at least) some of you. 211s have also other, more obvious advantages – sound is fast, tight, well differentiated, it has the drive, the slam – all that it takes to deliver high-end performance. How rich, full is the sound is partly speakers dependent – organs presented with Ardento OB proved that AirTight has all it takes. With Bassoon speakers (with four 20cm fullrange drivers delivering bass and midrange) organ didn't have same weight but the extension was also outstanding.

Midrange, as already mentioned before, is not so dense, creme as delivered by 300B amp (my impression anyway which surely comes also from more neutral tonal balance of ATM-211). Most 300B based amps emphasize midrange and although with well matched speakers also both frequency range extremes can be very good but never as fabulous as the midrange. ATM-211 offers more flat range with no emphasis on any part of it and that might trick the ears telling them that midrange is not so good as from my own ArtAudio Symphony II or ATM-300.

Just a short digression – my 300B amp offered the most flat, neutral sound when equipped my favorite Western Electric tubes were replaced with Japanese Takatsuki (offered by AirTight with their amps from the moment they ran out of WE stock). These outstanding Japanese tubes deliver much better extremes, creating more neutral sounding performance. These are a very strong competitors to legendary Western Electrics offering also top performance, crazy price and bit different sound character. Something 300B lovers should definitely check out.

Back to the reviewed amplifier – I think that anybody who is not so fixated on 300B-like midrange will love what ATM-211 has to offer in this area. It is a top quality SET after all! So its midrange is dense, liquid, smooth and colorful. Presentation is very palpable which come partially from very precise way of recreating a soundstage. It's about something more than just precise phantom images, great layering – the soundstage that you get is rock stable – just like in the real life. It starts aligned with loudspeakers fronts, it's very wide with Bassoon and quite deep (but not as deep as with my horn speakers or Avantgarde Acoustic Duo Omega). Precision is not the only advantage of this amp, it is also supported by unique resolution – these both features result in great transparency, many details but still sounding very natural. Comparing to my personal, favorite set that I'm really used to – 300B amp and horn speakers – here I wished for bit more emotions in vocal recordings, these could be also bit more palpable. This small difference was quite obvious to me at the beginning of listening sessions with 211s but the more time I spent with them the more I forgot that there even was any difference in this aspect. After three days tops I was ready to swear that ATM-211 offered me everything I could have expected in terms of timbre, emotions or palpability. As it could be expected from SET amplifier singers are usually shown in the front and the band, just a step ahead. Such amplifiers sometimes try to trick our ears – for example when Eva Cassidy signs and plays her guitar at the same time you might get an impression that voice comes from a closer spot in space than a sound of a guitar. AirTight won't do that – of course vocalist is shown in front but together with her guitar. What's more – you can clearly hear the sound of guitar coming from below Eva's mouth – that's as good reproduction of musical event as it gets.

Treble is also as good as it gets – detailed, vibrant, sparkling but also very open and with this particular softness that has nothing to do with rounding the edges of high frequency sounds, but is nothing if not natural. Each strike that reaches any cymbal carries the same “immediacy” I described in bass area. What seems to be a common feature of both AirTight amplifiers (ATM-300 and ATM-211) is a almost neutral tonal balance, which when compared with other SET amps might be perceived even as a cold sound as opposed to “standard” tube's warmth. But if you focus on the sound of this particular amplifier you will find it sounding very real – there is no tube's warmth in the midrange – it is simply real-sounding performance.

I should shortly mention also that thank to Polish Distributor I had a chance to compare standard power tubes with ones made by KR Audio. In fact I listened mostly with Czech tubes as I assumed that most potential buyers who will spare almost 50t PLN won't have any problem with adding 2000 more to get better sound. I'm pretty confident that 211s from KR Audio are better choice than standard tubes, even though the latter are marked „Premium” (most likely these are Chinese and I bet these are selected pieces only). These might be useful if your system in general delivers quite a dark sound, as they make ATM-211 sound bit bright, as the tonal balance is shifted up. They lack some of KRAudio's richness, and they don't sound so colorful – but the differences are not that big so it is up to the owner if he wants to have a bit better sound adding just a fraction of amplifier's price. If I could afford this amp I would invest in better tubes just to get maximum performance.

As I already suggested at the beginning of this text ATM-211 made it to my very short list of devices “to die for”. It is really very difficult to point out any weakness. Surely Japanese “purity” might not be very convenient – I mean single input and two volume controls (both somehow obvious for monaural amps), and 22W power output which is not enough for all loudspeakers – but these are features and not weaknesses, and a buyer accepts them when he chooses to buy this particular device. From sonic point of view I can't mention any weakness – surely I prefer to have some warmth in the midrange but this is about personal preference and not better sound. It is the ATM-211 that offers more real sound. With well matched loudspeakers this amp is fully capable of delivering each kind of music regardless of its genre, even if it is a dense piece of classical music or some extremely dynamic rock.


ATM-211 is a monaural SET amplifier with 211 power tubes. A 12AX7 (input stage) and a 12BH7A (driver) comprise the rest of the tube complement. It delivers 22 W output power in class A operation. Amplifiers are delivered with power tubes described as “Premium” (most likely from one of Chinese manufacturers) and the smaller tubes come from Electro-Harmonix. Luckily Polish Distributor offers as an option KR Audio power tubes (luckily in my opinion of course – if you buy these amps don't waste your time and ask for KRAudio power tubes).
A small practical advice for those unfamiliar with 211 tube – if you want to take it out of the socket first twist it and only then pull it out.
There are two pots on the front of each monoblock – one for volume control (it's a blue Alps), and the other that turns on bias meter. The very nice bias meter is placed on the top of the amp next to the 211 tube. If necessary bias can be adjusted with a trim pot accessible through a hole in the top of the chassis, although during all the time I tested amplifier there was no change in bias so no need to adjust it. Two pots for volume control might not be the most convenient solution (if you don't have a preamplifier), but on the other hand if you have only one source than you don't have to spend hell lot more money to buy a preamp good enough, plus you might use these pots to play with balance between channels (if necessary of course). Three fourths of the top of the casing are occupied by huge, beautifully finished transformers cups – these decide about specific look of this amplifier and possibly also about its significant weight. At the back there is a single RCA input, and WBT speaker posts. The latter are only single ones as to choose different than standard (8Ω) input impedance one has to solder cables to different tappings of output transformer (it is recommended to ask a Distributor for that).

Technical data (according to manufacturer):
Tubes: 211 × 1, 12AX7 × 1, 12BH7A × 1
Output power: 22W (8Ω)
Frequency response: 20Hz-20kHz (1dB, 22W)
Output impedance: 100kΩ
Dimensions: 390 (S) × 360 (G) × 260 (W)mm
Weight: 26kg (per piece)

Polish Distributor:

ul. Skrzetuskiego 42 | 02-726 Warszawa
tel.: 22 586 32 70, fax: 22 586 32 71

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