pl | en
Power amplifier
Air Tight ATM-300

Price: 32 000 zł

Polish distributor: SoundClub

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


WWW: Air Tight

Text: Wojciech Pacuła
Translation: Krzysztof Kalinkowski

Devices produced by the compant A&M Limited, which was founded by Mr. Atsushi Miura, under the brand name Air Tight are beautiful products, made with Japanese care about detail. I had the pleasure to meet Mr. Miura in person, during the last year edition of the High End show in Munich (2009) (reportage can be found HERE ). A rather not so tall person, like most Japanese, also not so very young anymore, but incredibly nice and openhearted, and when he heard, that I am from Poland, he became excited. We only exchanged a few sentences, but this meeting stayed alive in my memory, as it was kind of archetypical for meeting people from Japan, the true ones, not those already Europeanized and assimilated to the Western culture. Full esteem, care for detail and lack of hurry. This way of thinking is quite visible in the best products coming from that country, just look at devices proposed by Kondo/Audio Note, 47 Laboratory, Leben, Reimyo and others, even those bigger companies like Accuphase or Luxman. Air Tight is something special, especially due to the personality of its founder and the incredible manufacturing quality, as well as taste, with which those products are made. Let me remind a few facts of the company history:

  • 1956: Mr. Atsushi Miura joins Luxman.
  • 1961: Atsushi Miura marries the oldest daughter of K. Yoshikawa (the owner of the company).
  • Becoming a part of the family he becomes the head of sales in 1968, as well as general manager of the Tokyo office.
  • In the years 1977-1980 he works in the New York office of Luxman, leading its American division Lux Audio of America.
  • In 1985 (the Air Tight catalog quotes year 1986) he retires and together with Masami Ishiguro he founds the company A&M Ltd, and starts manufacturing the ATM-1 amplifier.

The amplifier received an award from the magazine “The Absolute Sound”: The Absolute Sound 2007 Editors' Choice Awards.

To date we tested:


I used the following discs for testing:

  • June Christy, Something Cool, Capitol Records/EMI Music Japan, TOCJ-90033, HQCD.
  • Julie London, By Myself, Liberty Records, MCR-1, LP.
  • William Orbit, My Oracle Lives Uptown, Guerilla Studios/Linn Records, AKH 351, 2 x 180 g LP.
  • Ariel Ramirez, Misa Criolla, José Carreras, Philips/Lasting Impression Music, LIM K2HD 040, K2 HD.
  • Firenze 1616, Le Poème Harmonique, dyr. Vincent Dumestre, Alpha 120, CD.
  • Jean Michel Jarre, Equinoxe, Dreyfus Music/Mobile Fidelity, UDCD 647, CD.
  • Kraftwerk, Tour The France Soundtracks, EMI Records, 591 708 1, 2 x 180 g, LP.
  • Dominic Miller & Neil Stancey, New Dawn, Naim, naimcd066, CD.
  • Pink Floyd, Wish You Were Here, Capitol/EMI, 5 29071 2, CD.
  • Art Farmer and Jim Hall, Big Blues, CTI/King Records, KICJ-2186, CD.
  • Depeche Mode, Fragile Tension/Hole to Feed, Mute Records, CDBONG42, SP CD.
Japanese versions of those discs available on CD Japan

Testing an amplifier of this class, built around this heavily codified, technology, it seems most reasonable to compare it to other, similarly built devices. Actually I know a lot of them, and we have even tested some at “High Fidelity”, just to name a few:

And although some of those are integrated amps, others power amps, still the technology remains same. And I mean, that those are fully tube based amplifiers, based on a power triode 300B, or equivalent, working in the output stage, in class A and SET setting, powered by a tube rectifier. In audiophile rings such amplifiers are worshipped like gods, and regarded as the absolute top, of that what is currently offered. And I do not want to engage in any discussions now (virtual ones, as I would need to respond to them myself), but I must confess, that although I do not agree with that in 100%, there is a lot of truth in those beliefs, and the 300B tube offers assets, not available anywhere else, at least to my knowledge.

One of those assets is incredible microdynamic and resolution of low level signals. Those are elements, which do not exist elsewhere in such form. The ATM-300 is not an exception to this rule. Every disc I listened to, and I listened to this beautiful amplifier extensively, were presented with an extremely well defined sound stage. And I am not even talking about the size of it, as this is a secondary issue when we are talking about this amplifier (the stage is very large, but nothing is blown out of proportion), but about the way the instruments, voices and effects are defined within its boundaries. Air Tight places all those elements in a very natural way, slightly “soft”, but not softened, just “not hard”. Whether it is a large church, where the Missa Criolla with Jose Carreras was recorded, or the interiors of a recording studio from Something Cool June Christy, or, finally, the artificial effects from the newest Depeche Mode single, in all cases the ability to show the stage as a whole, as well as its details in particular, letting us know, what role they play in the creation of the sound, were really outstanding. I think, that this characteristic, together with the very free reproduction of the sound as a whole plays a big role in creating this “admiration” I told you about. Because it is hard not to fall for it. Despite the mediocre 8W output power, the sound can be quite strong and loud. Seemingly the bass is limited on the very bottom (I am talking about frequencies below 40Hz), because more open amplifiers, like Reimyo, clipped much earlier. This is a limitation, that will probably not be audible on wideband, high efficiency loudspeakers, but this characteristic is handy when working with loudspeakers like my Harpia. And it played really, really loud.

Of course I managed to clip the ATM, but it sounded different. But before I come to that, I want to comment on the tonal balance this device has, as one is closely related to the other. Please note, that when I listed the 300B amplifiers in the beginning, I did not mention Ancient Audio, models Integra (integrated amplifier, a single 300B) and Silver Grand Mono (monoblocks, two parallel 300B). No, I did not forget them, but they do not mean one of the criteria related to cult amplifiers – their power supplies are silicon based, and not tube ones. Although the first version of the Silver employed the GZ34 tubes in the rectifying section, but their constructor, Mr. Jarek Waszczyszyn, stopped using them quite quickly. I witnessed those changes, and I must say, that they were beneficial for the product. But now I need to call upon those, especially the Silver Grand, because the sound of the Air Tight, especially regarding the tonal balance, reminds me much the sound of the Polish amplifier. The four amplifiers I mentioned earlier sound much warmer, had a visibly rounded top range and slightly boosted lower midrange. Compared with those, the ATM-300 sounds much more linear (but about this later) and much more neutral. This linearity means, that there is nothing “added” to the sound, because the midrange, especially in the lower part, is thinner. The sound of this amplifier, at least with the tubes supplied. Is much clearer and has less “intrusions”.

The treble benefits most. It is not as resolving as in the Grand, no chance for it, but it is better differentiated, more colorful, that in any other 300B amp I heard, maybe except for the Reimyo, which is at the same time warm and resolving… The vocals, which are elements placed in the middle of the frequency range, are a bit further away in the ATM-300 than in Reimyo and AA. Actually all the sound is placed further back, behind the loudspeakers.

The question how far back is mostly depending on the setting of the “Damping” switch, which selects the output impedance of the amplifier, what means selecting the depth of the negative feedback loop (at least I think so), and the higher the damping (and thus control over the woofers), the closer, and more palpable are the virtual sources, but also the sound volume gets lower (this is how the feedback becomes audible). This came handy with rock and strong electronic beats – only in this setting, the trance, dance beats from the double single from Depeche Mode Fragile Tension/Hole To Feed had the power they deserve. The solid state, 60W Luxman handled that much better, there was no doubt, that it can reach much lower, that the bas is better controlled and better differentiated, what means also better timbre, but the lovers of the sound from an 8W 300B tube should be born with knowledge about this limitations, and learn to live with them, as this is the sacrifice we need to make for this tube.

KR Audio 300B

ATM-300 came for testing equipped with Electro-Harmonix 300B EH tubes. But it can also be ordered with Western Electric ones (from current production), then the price will be 36000zl. Sounclub, the Polish distributor, has however supplied the KR Audio tubes, costing 1900zl a pair. The KR Audio tubes changed the sound, but not to the extent I expected. In general I must say, that the sound character was similar in the Harmonix and the Prague made tubes. That after a short listening session. In longer perspective, the KR Audio sound slightly softer, they are not as edgy as the EX, but not in the sense of upping the frequency range extremes, but in terms of differentiating the attack of separate sounds. This makes the Russian tubes more vivid, at least at first glance. But in reality, more open, more resolved are the KR Audio. Because they add more resolving upper midrange, and more vivid treble, atop of the EH. And although the attack of the sound as a whole is a little softened, the addition of extra information makes the treble sound fuller. I said before, that the ATM-300 is not a dark or warm amplifier. The Czech tubes confirm that, but are a less mechanical way, than the Electro-Harmonix, which had a very clean, but not so saturated treble. I mentioned also a slight lack of “body” in the previous configuration – the KR Audio make that disappear, to some extent. Like I say, this is the same characteristic of the sound, but there is more of everything, everything gets clearer. The only element I liked better with the Russian tubes was the bass – the KR Audio round it off a little, make it softer. This is not a big thing, but it will be audible with lowest notes.

Crèate Audio 300B + 12AU7 and a preamplfier

Changing the KR Audio to Crèate Audio moved the tonal balance upwards. The resolution went clearly up, previously unheard elements went to the sound, but I am not sure, if this is the right direction. I think, that the ATM-300, having a strong and clean treble with EH or even KR tubes is on the verge of being tonally correct. Adding more information makes the device clip earlier, and the tonal balance moves to the upper midrange. I was also curious, how the Japanese amplifier will behave, when in this situation, a preamplifier will be placed in the sound path. Usually the sound gets fuller and smoother. This was not the case this time, so I returned to the KR Audio tubes. Adding a preamplifier has rather complicated the case, than resolved it. I did not feel any increase in dynamics, space or vividness. At the same time the resolution diminished. This is the reason, that I recommend to use the volume control the Air Tight provides. The input impedance of the power amplifier is so high, that even a CD player output, at 2V, will be enough to create high volume levels in a room. It would be even better, if a player would have a higher output voltage than the standard – some players, like Wadia or Ayona allow to select it. And the tubes? It would be best to select carbon type tubes, and not mesh types – like the Sophia Electric Princess 300B/c (review HERE), or order the amplifier with Western Electrics.


ATM-300 from the company Tight is nominally a power amplifier with regulated input sensitivity. But because it is quite high (230, 300 or 450mV, about that in a moment), and fluent regulation can be done from -∞ to 0dB, so we can treat it as an integrated amplifier with only one line input. The unit is fully tube based. Input is handled by two double triodes 12AU7A (ECC82 EH) from Electro-Harmonix, both halves working in parallel. The tubes carry also the Air Tight logo and are marked “Platinum Selection”. This means, that the tubes were measured, and paired with low tolerance. When I talked about such selection with people from Canor, they told me, that about 80% of the tubes are rejected during a similar process! From the input tubes the signal goes to the control tubes – larger, but still low power triodes, 12BH7A, also coming from EH. In the output stage 300B triodes are employed, in SET setting, one per channel. The ATM-300 can be ordered with different tubes – I received it with Electro-Hrmonix tubes from current production. And the power supply – rectified by a 5U4GBEH rectifier from the same tube factory, also in Platinum Selection version.

The amplifier has a classic looks for this type of devices, meaning a low profile chassis, with all the tubes and transformer cups placed atop. The chassis is made from extremely well crafted aluminum profiles, anodized grey. It looks terrific, and I would wish every manufacturer, to get such a precision in their products. On the front panel we have three knurled knobs – two are for volume control (separate for right and left channel) and one for bias setting. A small voltmeter is used for that action, placed next to the golden company logo. Furthermore we have only a power switch with indicator led. The connectors are not placed on the back plate, as usual, but on the top one, behind the transformers. We have there a pair of RCA inputs, and two pairs of loudspeaker terminals – gold plated WBT 0735 – and an IEC power socket. Please note, that the loudspeaker terminals are singular, but the output transformers have windings for 4, 8 and 16Ω - each value is available, but this needs to be consulted with the distributor, and he can change the output connected to the terminals upon request. On the top plate we have all the tubes and transformers. The power transformer is made by Air Tight, while the loudspeaker transformers are something special – they are wound by Tamura Seisakuscho Ltd., a known Japanese specialist. Here it is the model F-2007. Between the tubes, there is another, very important element – a three position switch called “Damping”. It sets the feedback level between 0, 4 and 6dB. The change of the NFB changes also the input sensitivity – the higher the loop, the lower the sensitivity. The unit is supported by solid feet, made from stainless steel and micro-rubber.

The bottom plate of the amplifier is made from a beautifully copper plated plate, which serves and an RFI shield. A similar plate, albeit smaller, serves as the mounting support for tubes and other elements. The internal connections are made point-to-point, using supporting montage elements. The circuit employs almost only Sprague capacitors (expensive), with orange polypropylenes connecting the individual stages. In the feedback loop and signal path NOS resistors were used. Cathode resistors for the 300B tubes are mounted on heat sinks, and come from Dale. The anode current is rectified in the tube, and then goes to a classic Pi type filter, but with a resistor in the first stage, and a large choke (wound by the company itself) in the second stage, where the voltages for the output stage are drawn. Current for heating is rectified and stabilized. The output tube bias is automatic. Everything looks very nice. One more thing – the signal goes via cables from the back to the front, where shielded, single Alps Blue Velvet potentiometers were placed.

Technical data (according to manufacturer):
Tubes: 300B x 2, 5U4G x 1, 12BH7A x 2, 12AU7A (ECC82) x 2
Output power: 8W + 8W (8Ω)
THD: < 1% (6W)
Input sensitivity: 230, 300, 450mV (selectable)
Damping: 0, 4, 6dB (selectable)
Dimensions: 430 (W) x 275(D) x 245 (H) mm
Weight: 24kg

The French magazine “Son&Image” tested this amplifier in 2006 (May-June) – the measurements made during that test were as follows:
“The parameters were depending on the chosen feedback loop depth. At 0.9% THD, output power in position 1 was 3.5W RMS per channel, in position 2 – 5.8W and 6.2W in position 3. In all positions the frequency response is (+/- 3dB) 20Hz-20kHz and is ideally flat in positions 2 and 3. Clipping occurs from 7.1 W, and at 8W THD equals 7%. At 1W THD is 0.16%.”

The whole test can be found HERE.

g    a    l    l    e    r    y


  • CD player: Ancient Audio Lektor Prime (tested HERE)
  • Phono preamp: RCM Audio Sensor Prelude IC (tested HERE)
  • Preamp: Leben RS-28CX (tested HERE; soon to be changed to Polaris II, tested HERE)
  • Power amp: Luxman M-800A (tested HERE)
  • Integrated amp: Leben CS300 (reviewed HERE)
  • Loudspeakers: Harpia Acoustics Dobermann (tested HERE)
  • headphones: AKG K701, Ultrasone PROLine 2500, Beyerdynamic DT-990 Pro, 600 Ω version (reviewed HERE, HERE, and HERE)
  • interconnects: CD-preamp: Wireworld Gold Eclipse 52 (tested HERE; soon to be changed to Acrolink Mexcel 7N-DA6300, article HERE), preamp-power amp: Velum NF-G SE (tested HERE)
  • speaker cable: Velum LS-G (tested HERE)
  • power cables: Acrolink Mexcel 7N-PC9100 (CD; reviewed HERE) and 2 x Acrolink Mexcel 7N-PC7100 (preamp, power amp (reviewed HERE)
  • power conditioning: Gigawatt PF-2 Filtering Power Strip (reviewed HERE)
  • audio stand Base
  • resonance control: Finite Elemente Ceraball under the CD (article HERE ) Turntables change continuously, as do cartridges. My dream setup: SME 30 with Series V tone-arm and Air Tight PC-1 cartridge (also in the PC-1 Mono version).