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Power amplifier | monoblocks

Air Tight

Manufacturer: A&M LIMITED
Price (in Poland): 280 000 PLN/pair

Contact: 4-35-1 Mishimae | Takatsuki-city
Osaka 569-0835 | JAPAN


Provided for test by: SOUNDCLUB

„In 2001, Air Tight introduced the ATM-211 power amplifier, which with its 22W output satisfied the owners of high-sensitivity speaker sets. However, many people expected a tube amp that, while offering the top quality sound, could provide power exceeding 100 W" (source: company materials). We are testing the fulfillment of these dreams, the ATM-3211 monoblocks.

he Japanese company Air Tight is a "retirement project" of Mr. ATSUSHI MIURA and his friend, Mr. MASAMI ISHIGURO. The word 'retirement' is not accidental here. Miura-san worked throughout his entire professional career at Luxman and only after closing this chapter of his professional life, sort of in his "free time", he founded the Air Tight:

  • 1956: Mr. H. Hayakawa employs Mr. Miura at Luxman as an electronics engineer (Lux Corporation was founded in June 1925 by Messrs T. Hayakawa and his brother K. Yoshikawa; this is the oldest Japanese audio manufacturer)
  • 1961: Atsushi Miura marries Mari Yoshikawa, the eldest daughter of Kingjayi Yoshikawa, becoming a member of the family
  • In 1968 he become the Sales Director and a senior manager in Tokyo office
  • Between 1977-1980 he works in the Luxman's New York office, heading the American branch of the Lux Audio of America
  • 1982: Mr Miura returns to Japan. The company is in crisis – due to oil crisis cost of production in Japan achieve very high level. Also there are some newcomers to audio industry, such as Sony or Sanyo, selling affordable solid-state products. Mr Miura sells Lux Audio (Luxman) to a French company called Alpine
  • In 1985 he retires and, together with Masami Ishiguro, he develops a prototype of the ATM-1 amplifier
  • In 1986 both gentlemen found in Osaka a company called A&M Ltd., with the ATM-1 being their fist product, which is still in production today in its updated version
  • 2006: The company's growth forces owners to move the factory to Takatsuki, a city half-way between Kyoto and Osaka
  • 2017: The official presentation of the ATM-3211 amplifier

As you can see from this short summary, Air Tight was created out of the heart's needs - in the mid-1980s tube amplifiers were rare, and the renaissance of this technique was still waiting to happen. According to Mr. Miura and Ishiguro, the sound quality offered by commercial transistor amplifiers was simply too poor, so they decided to present their project to the world.

| ATM-3211

Mr. Miura grew up surrounded by engineers and entrepreneurs in a family business. It just so happens that Air Tight is also a company of this type. For several years, the duties of a designer, and for some time also a director, have been performed by Mr. Yutaka "Jack" Miura, son of Atsushi Miura. Born in 1934, the senior of the family retired, this time for real. He still goes to audio shows, including the one in Munich, but rather as an icon. The company is currently managed by his son.

Jack Miura re-designed the ATM-300 amplifier to the latest ATM-300R version, that we reviewed in May this year (HF | № 181). As he said in the „Stereophile”, he re-designed the power supply, used a different type of iron in power transformers and choke („Stereophile”, accessed 01.10.2019). The ATM-3211 is his own project.

This amplifier was first presented in 2017 at the CES 2017 in Las Vegas. It consists of two monoblocks with triodes throughout the whole signal track. The input features a 12AX7 double triode, operating in a differential circuit, and the output tubes, the 211 triodes, are driven by three 12BH7 double triodes, in the Cathode Follower circuit. The output tubes are therefore coupled to the control section without the use of capacitors. The 211 are power triodes. To get 120 W, because that's the maximum output of the ATM-3211, they must operate in a push-pull circuit. They work in AB class, but up to 30 W remain in class A.

| 211

The 211 is one of the best-known directly-heated triodes. We know its most famous application from the Kondo OnGaku amplifier. There it worked in class A in single-ended mode, delivering up to 27 W per channel. In 2001, to celebrate the arrival of the new millennium, Air Tight presented the ATM-211 monoblocks, 22 W output achieved with a single 211 tube per channel.
The 211 is a powerful, four-pin tube with a bright color of light emitted by it. It was developed in the 1920s in the USA as an emission lamp for high power AF and RF transmitters, as well as a lamp for oscillators. It can work in class A, AB or B. Its anode voltage is usually 1000 V, but it can be supplied with up to 1250 V. Compared to the 2A3 and 300B tubes, its characteristics are much more linear. Currently it is manufactured by several companies, primarily Russian and Chinese, but the highest prices achieve NOS units, costing $ 3,000 and more.

The ATM-3211 amplifier features a characteristic appearance due to the titanium front panel and almost square base contour (400 x 450x 405 mm). Monoblocks weigh 44 kg (pc), and this is because they utilize very large transformers – output ones by Tamura and power ones wound in-house by Air Tight. Two large 211 triode bubbles are visible in the front, and control tubes are placed at the back, right next to the input. This is a very good solution, reminiscent of classic McIntosh and QUAD amplifiers, and further developed by the French company Jadis. The signal path is thus shortened.

The company claims that the use of - moderate - feedback helped them to achieve a wide frequency response. According to them, with a drop of just 1 dB, a bandwidth of 10 Hz to 50 kHz was obtained. For a tube amplifier this is a very good result. The device is manufactured only upon order and looks simply great. It is now a reference amplifier from Air Tight.


The ATM-3211 monoblocks are so large and so heavy that they had to stand in front of the Finite Elemente Pagode Edition rack, directly on the floor. They were powered by Acoustic Revive Absolute Power cables, and connected to the Ayon Audio Spheris III preamplifier using the Acoustic Revive Absolute-FM interconnects. The signal source was the Ayon Audio CD-35 HF Edition player (№ 1/50). The amplifiers drove the Harbeth M40.1 speakers using Siltech Triple Crown cables, but I also used NOS Western Electric cables, with good results :) The ATM-3211 were compared to the Soulution 710 power amplifier, and together with the Ayon Audio preamplifier to the Vitus Audio SIA-030 integrated amplifier.

AIR TIGHT in "High Fidelity”
  • TEST: Air Tight ATM-300R | power amplifier
  • TEST: Air Tight PC-7 | cartridge
  • TEST: Air Tight ATM-2 | power amplifier
  • TEST: Air Tight ATM-211 | power amplifier
  • TEST: Air Tight ATM-300 | power amplifier
  • TEST: Air Tight PC-1 Supreme | cartridge
  • TEST: Bergmann Audio SINDRE + Air Tight PC-1 | turntable + cartridge
  • TEST: Air Tight ATC-3 + ATM-1S | preamplifier + integrated amplifier

  • Recordings used for the test (a selec- tion)

    • Brian Eno, Another Green World, Virgin/Astralwerks 7243 5 78034 2 7, „Original Masters”, Master CD-R (1975/2004)
    • Dave Grusin, Discovered Again! Plus, Sheffield Lab/Lasting Impression Music LIM XR 002, XRCD24 (1976/2003)
    • Mark Hollis, Mark Hollis, Polydor 537 688-2, CD (1988)
    • N. Maeda, N. Maeda Meets 5 Saxophones, Audio Lab. Record/Octavia Records OVGL-00026, SACD/CD (1976/2012)
    • Oscar Peterson, Exclusively For My Friends, MPS Records/Edel Germany 0210325MSW, 8 x CD (2015)
    • Patricia Barber, Companion, Premonition Records/Mobile Fidelity Sound Lab UDSACD 2023, SACD/CD (1999/2003)
    • Stan Getz/Joao Gilberto, Getz/Gilberto, Verve/Lasting Impression Music LIM K2HD 036, K2HD Mastering, „24 Gold Direct-from-Master Edition UDM”, Master CD-R (1964/2009)
    • Vangelis, Blade Runner, Atlantic Records/Audio Fidelity AFZ 154, „Limited Edition | No. 2398”, SACD/CD (1998/2013)
    • Various, For The Masses, 1500 Records | A&M, 540 919-2, HDCD (1988)

    Tubes, triodes, class AB, feedback, push-pull mode - each of these techniques may inflame some heated debates between audiophiles. They are ready to do that instead of focusing on the most important issue: how do these monoblocks sound like? Each of the designers' choices, combining several of them in this one and not a different configuration, affects the sound, changing it in a way characteristic of a given technique. Because - yes, indeed, specific techniques have a repetitive set of features that can be pointed out in almost every device.

    On the other hand, looking for them and basing the whole design on one of them is a mistake, even stupidity, one can say, because there is no such thing as "pure technique". There are only their interpretations and combinations. Therefore, what I mentioned above - "how does it sound?" is the most important and (…...) technique (in parentheses you can insert any verb of your choice in the infinitive mode).

    We can reach such conclusions by listening to consecutive albums with the Air Tight amplifier. We will hear such a richness of sounds that we will start to take new albums out of the shelves with curiosity, driven by the desire to learn the truth, deeper truth and finally the absolute truth. The Japanese amplifier engages us in something that can be called a "game for everything", that is, the search for the "Holy Grail" or whatever you want to call it.

    Its sound is lively and exciting. This is an open, powerful sound with a clear, large, close foreground. It has nothing to do with the foreground of warm amplifiers, the push it artificially towards listeners, and rather refers to what I know from the recording studios, when through studio monitors, you can hear the direct transmission from microphones before it is even recorded on the tape or in the computer's memory. This is a unique foreground that has the right proportions, timbre and specific "here and now".

    The proportions are exceptionally well preserved by this amplifier, one could say that it is exemplary. When in the The Gift track from the Mark Hollis album - a vinyl reissue was just released – drums enter, you get the feeling of being in the studio where the recording had been recorded. The fact that the recording was made using two microphones helps in achieving this effect. But it was due to the direct sound of Air Tight that it was rendered so faithfully.

    Certainly, dynamics plays a big role in creating such a natural and lively performance. Usually, it is associated with high power, although in reality it needs to be connected with resolution, as here, to make sense. At least, if we are talking about full-range, tone-aligned speakers. The tested amplifier plays any, I mean any material effortlessly. I could easily tell that it had enough power to present huge dynamics shifts, like from masters to - yet unreleased - Oleś Duo disc Alone Together, which were presented with equal attention and without compression, as with my Soulution 710 amplifier. Even the beautiful Vitus Audio SIA-030 amplifier was in this regard slightly more conservative, slightly withholding the sound attack.

    Maybe this is not due to power, but resolution. Because this device is extremely "transparent" to the signal source. It presents such a richness of colors as hardly any other amplifier, except for Kondo OnGaku and Ancient Audio Silver Grand Mono; even my Soulution is in this respect a bit worse. So differentiation is above average, and - to be honest - exceptional. With all this truth telling, the amplifier does not work like a lens, it does not focus our attention on recording errors. Yes, you can hear them, you can clearly hear the differences in the recordings and releases. However, we are not punished for it.

    After all, listening to music is not about self-whipping. It should offer entertainment on the one hand, experiencing a unique event on the other, and complementing something that awaits music within us on the third. A deeper need. The Air Tight will provide us with all that. Listening to the next recordings from the For The Masses, on which artists such as The Smashing Pumpkins, The Cure, Apollo Four Forty, and finally Rammstein, play their versions of Depeche Mode songs, I could hear changes in the studio, including how the piece was recorded and mastered.

    Not all of them are perfect, it is a classic example of a recording for masses. But even when I heard stronger sibilants in the voice of Nina Gordon, the vocalist of Veruca Salt, beautifully performing the Somebody, it was not a flaw. For the first time, if I am not mistaken, I heard it in my system as if in the studio. In the real world there is a lot of treble in the human voice, but we do not pay attention to it. Recordings have a problem with it, because it is usually distorted and it is the distortions of sibilants that “pop” from the mix, and not them themselves.

    With the ATM-3211 I could hear that the microphone was close, that the compression was high and that on the mastering engineer forgot about the upper midrange. But despite all that it was perfectly natural, because believable sound. I would like you to understand me well - bad recordings will remain bad with this amplifier. It's just that their technical disability will be withdrawn behind music, or even behind the performance.

    The more so that the amplifier sounds in an extremely intense way. Which is different from what I know from OnGaku, other than with Phasemation, Vitus and Mark Levinson. They all show the world in a slightly enhanced way, better than it really is, and they do it brilliantly. However, you can do it differently - it doesn't mean that it's better, just different - like with Air Tight. You can't listen to music in the background, in passing with it. It's a device that requires focus. We take the disc out of the box, covers, select a music file with a specific intention - to listen to the entire album.

    It will be an album recreated with rich colors, high dynamics, intensity, differentiation and a reliable soundstage. The Japanese amplifier shows a large, three-dimensional space with extraordinary tangibility. It is not a master at showing the depth of the stage, but rather focuses on what lies ahead. It perfectly differentiates the location of instruments in space, their bodies and interaction with the room. It's just top high-end. The bodies themselves have a rounded shape, they are not internally differentiated in any unique way. Only the best SET amplifiers can do that. However, I did not miss anything in this respect, it is simply one of the choices we have to make.


    Air Tight offers amplifiers based on the 211 tube operating both in SET and push-pull mode. So you can choose. But every time it will be a choice between different values, you can't have everything. With the tested model we will get an incredibly natural sound, but rather the one that can be heard in the studio, without the interface of the recording medium, i.e. without beautifying and refinement.

    It is a lively, dynamic, open sound with a strong foreground. If the rerecording is made with a microphone close up, it is immediately shown. When the source is away from the microphone, we will hear it immediately too. The sound is very clear, fluid and rich with information. Details are not emphasized, because music is not about them. In turn "events" are almost tangible, vivid and credible.

    This is one of the few tube amplifiers that retain the magic of this method of signal amplification and at the same time allow you to use almost any loudspeakers, listen to any album without narrowing our repertoire to vocal music and small jazz compositions. This is one of the few amplifiers that I would really like to have. That's why I have to present it with highest distinction, the GOLD Fingerprint.

    The Air-Tight ATM-3211 is a monophonic power amplifier. The amplifier, weighing 44 kg, has a concentrated mass in a very small area, so two people are needed to move it. To facilitate this, two large handles are screwed to the rear.

    Front | The amplifier's front is made of 15 mm thick aluminum plate, anodized with the company's characteristic titanium color. There is a mechanical power switch and a large, VU meter useful when setting the bias for output tubes. There is no denying that it also plays a decorative role because it looks really nice.

    Rear | The back of the amplifier is not as empty as one would expect from a power amplifier. The signal is fed to the RCA input - it is an unbalanced amplifier. The socket is solid and comes from the WBT. Next to it there is a knob which allows user to adjust input's sensitivity - it is simply an attenuator. The nominal input sensitivity is 1 V, but if we have a preamplifier with high gain or high efficiency loudspeakers, this attenuator can be very useful. And there is also a switch allowing user to choose which tube one sets the bias for. In the middle of the rear panel there is a pair of gold-plated speaker sockets. Also they were sourced from WBT.

    Upper side | Usually the top of an amplifier is boring, but not in the case of some tube amplifiers. In this case there are two, very large housings encasing an output transformer and - well, to tell you the truth I do not know what is in the second one. The former, just like the choke, is made by Air Tight in-house, using a new type of spacers. The output transformer is purchased from the famous Tamura. By default, ATM-3211 is delivered with a 6 Ω impedance output, but a 16-ohm version is available on request.

    Obviously there are also tubes. Two 211 triodes are placed in the front, in large, aluminum covers for their bases. Air Tight has chosen Psvane tubes for this amp. The input and driver tubes sit in the back, right next to the input Such a shortening of the signal path is a great idea. The input operates with a 12AX7 double triode, in a differential circuit, and the 211 triode is driven by three 12BH7 double triodes, in a Cathode Follower circuit. All small triodes were produced by the Russian company ELectro-Harmonix.

    Inside | The bottom of the device is made of thick, copper sheet, with five feet screwed to it - one in the middle. To further strengthen it, a steel cross was screwed from the inside. The electronic circuit is assembled using the oldest known method - point-to-point. It means that instead of a printed circuit board, the components outputs are soldered directly to each other or to wires, usually made of thick copper.

    If I am not mistaken, the vast majority of components come from Japan, the USA and Germany. The layout inside is divided into two main parts – gain stage and power supply, with elements attached to thick, copper plates. The gain stage features high-precision resistors and Auricap XO coupling capacitors from the American company Audience. The attenuator in the input section comes from the Alps company.

    The oversized power supply is based on a huge transformer and a choke for the anode section. I counted five separate rectifiers, with integrated rectifier bridges for the filament section - output and driver tubes separately - as well as Shottky diodes in other sections. Filtering capacitors come from the German company F&T. Resistors come from Takman, Dale etc.

    That's a beautifully built device.

    Technical specifications (according to manufacturer):

    Output: 120 W (6 Ω, TDH 2%)
    Frequency range: 10 Hz-50 000 kHz (±1 dB / THD 0.06%/1 kHz/ 30 W)
    Input sensitivity: 1 V
    Input impedance: 100 kΩ
    Damping factor: 7 (1 kHz / 1 W / 8 Ω)
    Load impedance: 6 Ω (standard) | 16 Ω (upon request)
    Power consumption: 550 W
    Dimensions (W x H x D): 400 x 450x 405 mm
    Weight: 44 kg


    Reference system 2018

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    2) Line preamplifier: AYON AUDIO Spheris III Linestage |REVIEW|
    3) Super Audio CD Player: AYON AUDIO CD-35 HF Edition No. 01/50 |REVIEW|
    4) Stands (loudspeakers): ACOUSTIC REVIVE (custom) |ABOUT|
    5) Power amplifier: SOULUTION 710
    6) Loudspeaker filter: SPEC REAL-SOUND PROCESSOR RSP-AZ9EX (prototype) |REVIEW|
    7) Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|


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    Speaker cable: SILTECH Triple Crown (2.5 m) |ABOUT|

    AC Power

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    Power (2 m) |ARTICLE|
    Power cable | Mains Power Distribution Block - Line preamplifier - ACOUSTIC REVIVE
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    Power cable | Mains Power Distribution Block - Power amplifier - ACROLINK Mexcel 7N-PC9500 |ARTICLE|
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    Anti-vibration platform under Acoustic Revive RTP-4eu ULTIMATE: Asura QUALITY RECOVERY SYSTEM Level 1 |REVIEW|
    Power Supply Conditioner: Acoustic Revive RPC-1 |REVIEW|
    Power Supply Conditioner: Acoustic Revive RAS-14 Triple-C |REVIEW|
    Passive filter EMI/RFI: VERICTUM Block |REVIEW|


    Speaker stands: ACOUSTIC REVIVE (custom)
    Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|
    Anti-vibration platforms: ACOUSTIC REVIVE RAF-48H |ARTICLE|

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    Clamp: PATHE WINGS Titanium PW-Ti 770 | Limited Edition

    Record mats:


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    Headphones: Headphone Cables: Forza AudioWorks NOIR HYBRID HPC