Jun 042011

Introduction and confession

I like integrated amplifiers, you know where you are with an integrated and by using one you remove two levels of potential difficulty you have with a pre-amplifier and power-amplifier combination; namely compatibility between the pre and the power (unless they are from the same brand and even that does not guarantee full compatibility) and the suitability/compatibility of the connecting cable. There is also the added expense of two mains cables (if you are using after-market ones), needing to use two shelves of your equipment table and a number of other potential cost and compatibility issues. With an integrated you only have to concern yourself with matching a source, speakers and cables; once you have that in the bag the jobs a goodun!

So why bother with a separate pre and power amplifier? Well put simply there are sound quality benefits which outweigh any additional pitfalls you might come across. Firstly there is a sound quality benefit by separating the delicate source signals into a separate box away from the strong magnetic fields created by mains transformers. Secondly there are further benefits to be had by having separate power supplies for the pre-amplifier and power-amplifier stages.

You may say, “Well surely you could build an integrated that way,” and you would be right. Some audio companies do but these, ‘Super Integrated’s’,  end up being massive, very heavy and in some cases as dear as a separate pre-power. There is also the issue of having to add lots of shielding internally to gain a similar benefit to having two separate boxes.

So why say’ you like integrated amplifiers’ at the beginning of this review? You may ask. Well they are simpler to review in most cases and integrate into an already existing system; such as my reference system more easily.

Before delving into this review more deeply I need to fess up right at the beginning and say I don’t consider this a finished review but more a fairly big series of leaps towards the end of one. So why publish an unfinished review? Well I feel I have dug into the product in for review enough to be able to give you dear reader a fairly good idea of what it sounds like. However what I have not been able to do is get the absolute full measure of this amplifier because I have been unable to use it with a pre-amplifier I have (or have been loaned) that is both transparent enough to match it, nor one that is 100% fully compatible on a technical level.

During the course of this review I mostly used the amplifier by not using a pre and wiring a source directly into it. This worked well but from both a practical point of view and a soundquality one, based on things i heard during this review I feel the AirtTight ATM 300 would sound much better being used with a pre-amplifier than not being used with one (1)

These factors, however are not the fault of the AirTight ATM300 amplifier but are indeed simply down to me failing to deliver it an ideal set of review circumstances. However despite this I still feel that it is worthwhile publishing my findings to date; so here goes.

The Journey

Sometimes starting a review is like taking a journey on which one is not quite sure where one will end up but then there are times when you are pretty sure you know where you will end up having all ready read the destination guide. Well this particular journey with the ATM 300 has been very interesting indeed but before dipping  our collective toes into the review proper it is important to have a look at the technical aspects of the amplifier.


The Airtight ATM 300 is a class A stereo power-amplifier using a pair of 300B valves to produce around 8 watts (as with most valve amps it sounds way more powerful than the figures suggest) per channel. It has separate left and right attenuators which would allow the end user to use at a single source integrated amplifier or with them opened up fully as a stereo power-amplifier.

The amp also offers a 3-position (0dB, 4dB, 6dB) “damping control” to optimize negative feedback. I felt in my set ups that setting 1 sounded best. This particular amplifier was supplied to me with a pair of Shuguang 3ooB-Z Treasures and was well run in before I was loaned it (the unit is even self-biasing, although a handy bias-current meter lets you check up on the state of the tubes while playing), making for stable, fuss-free operation. The output transformers are like the internal components of the very highest quality and are in the case of the ATM 300 made by Tamura.

Internal point to point wiring is of first rate quality as is the external fit and finish. Frankly while this is an expensive, almost bespoke product (Airtight products are not made in big quantities) handling it and using it fills you with a kind of reassurance and appreciation of the exceptional quality it embodies and hearing it….well that would be getting a wee bit ahead now.

System Used

While I try always to use my main system for reviewing I found myself on this occasion unable to use my Anthony Gallo Ref 3.1’s as this speaker did not work particularly well with this amplifier. It was pretty clear cut that 8 watts, even a very good 8 watts was not going to work. Being honest I knew this would be the case right from the off before even trying it but one tries these things in the pursuit of knowledge and the flat lifeless bass light sound only came forth from the speakers for a few minutes proved my earlier gut instinct correct.

As my upstairs set up is just as good as the downstairs system but just on a smaller scale, I decided to decant the AirTight from the main set up and carry it up to the second system; where while it worked better, it was still not right. In this case though the issue was down to a mismatch with my BAT VK 31se’s RCA output impedance and also the amount of drive available to the power-amplifier from the BAT’s RCA output (further playing around with other pre-amplifiers has proved interesting. More on that a bit later on)

It is times like this that my large collection of equipment, that I  have stored away, comes in very useful, as I still own a pair of excellent speakers that I instinctively new would work with the AirTight; these being a pair of Ruark Equinox’s, one of this British companies finest stand mount speakers. When I installed the Anthony Gallo’s in my main system I just could not part with these lovely speakers and after reinstalling them downstairs, a task made easy, as I had kept the tape on the floor that marked their optimal position, from when I had originally used them regularly; I knew I had a winning combination from the first few notes of the CD I played, or so I thought initially.

Alas while getting the speakers right I now felt, after some listening, that things were still not quite optimal for an in depth assessment of the amplifier; so I tried a few more combinations of cabling and isolation. This resulted in me moving the amplifier from the Mana amplifier stand to the top shelf of my Clearlight Audio RDC Aspekt rack (in part to see how this sounded but also to allow me to try some cables that were not long enough to reach the amplifier when sited low down), trying Atlas Mavros RCA to RCA cables, Harmonixs Golden Performance RCA to RCA cables and a Harmonix XDC 2 mains cable, until I was happy things were as good as I could get them to be.

Ultimately I ended up feeling that the following components gave the most optimal set up (please keep in mind – in the context of my system, room and music): Moon Andromeda CD player, no pre-amplifier (more on that later), Atlas Mavros speaker cable, Audience AU24 RCA TO RCA interconnect cable, Audience AU24 mains cable, Ruark Equinox speakers and three Sound Mechanics M8 domes under the amplifier.

Music Used:

The Dali Demo CD

Nightmares on Wax – Carboot Soul

Nitin Sawhney – Beyond Skin

Robert Downey Jnr – The Futurist

Rain Tree Crows – Rain Tree Crows

Thomas Dolby – Aliens Ate my Buick


The main issue that was becoming fairly evident to me was having a suitable pre-amplifier to match the Airtight ATM300. My regular Meridian G02, while very good just seemed wrong as was the Chapter Audio Preface Signature, EAR 864 and my BAT VK31se as evident from its failure upstairs. Having heard the AirTight before I knew that the sound I was getting was just not right with a lack of the magical qualities I know this amplifier has. You might say that my previous experiences hearing an ATM300 at a HiFI show and in another system was giving me a dose of rose tinted spectacles but I knew this was not the case, so with technical issues and obvious veiling of the sound I opted to hook the AirTight directly to my Moon Andromeda and Marantz SA7 and after a few minutes with either source it was very clear I had been right the ATM300 could and did deliver more in my system without the veiling effect my pre-amplifiers were introducing to proceedings. However I really need to stress here that this was down to the pre-amps I had tried not being suitable and not a case of this amplifier being best used without a pre; in fact another experience a bit further down the review road suggested strongly that a pre-amplifier in the signal path would bring some extra sound quality benefits but I am getting ahead of myself a bit.

This amplifier now had, clarity, dynamics, weight, scale and musicality in spades and if you think valve amplifiers sound soft or muddled then hearing one of these in the right setting will, if you have a pulse, ears and an open mind disavow  you of that notion. I have heard soft valve amplifiers and soft, warm cuddly 300B using valve amplifiers but the Airtight ATM300 is neither of those things. Its sound sits just to the warmer side of neutral but only just and with an inappropriate mixture of components it is just possible to end up with a bright sound (I did early on manage to achieve that), though only just.

There was enough gain with the amplifiers level adjusters usually no more than half way round give or take a few positions depending on the vintage of the recording. Newer recordings or re masters with more loudness and dynamic compression required less adjustment of the levels. With the Ruark speaker’s 8Watts was going quite a long way and in fact I never felt at any stage that the ATM 300 was running out of steam even on the most demanding music I threw at it.

One great strength that became evident fairly early on was the even handed way it amplified poor recordings. Yes it told the story as to how and why the recording was not up to scratch but it never shouted this and it always managed to unlock hidden musical qualities no matter how bad things were recoding wise. I was very impressed with this ability to be musical at all times. Some amplifiers can do this but usually at the expense of transparency and those that go down the ultra transparent road end up sounding unmusical and nasty when a recoding is poor. It can be argued of course that that is just as it should be, nasty recording equals nasty reproduction; however as many if not most recordings are non-audiophile and therefore less than idea in audiophile terms, to varying degrees, is it not a more desirable trait to be honest but not lose musicality in being too honest? I guess it’s a preference but as I get older I prefer honesty which is as musical as it can be and the AirTight ATM 300 amplifier has this quality in spades.

Curious to see how the AirTight sounded in the upstairs system I once again took its not inconsiderable weight back upstairs. It sat on a wooden base board with Track Audio Isolators screwed in underneath and hooked directly to my AMR CD-77 (using Audience AU 24 RCA interconnect cable) and I played some of the music I had been using downstairs (as listed above) I found that the initial earlier failure upstairs due to it being incompatible with the Bat pre ( not enough gain, even using balanced from such as my Marantx CD7)  it was now sounding wonderful; with the direct connection to the AMR CD players RCA outputs. All the qualities I had heard downstairs were evident upstairs too just in a slightly smaller way (the Ref 3A Dulcet’s are not by any stretch of the imagination full range speakers). There was excellent image depth, image height and width too. In fact the speakers in this room were constantly vanishing while listening to music via the AirTight.

A Knight to the rescue

At around about this time a new element entered the equation and while I am reluctant to mention items just in for review before they are reviewed themselves properly I feel I would really be remiss if I didn’t in this one case.

During the just past London Heathrow Audio world 2011 show I was very impressed with the sound and build quality of some new to me products from a company called Stereo Knight. I hit it off with their UK distributor Iain Borthwick and he offered to loan me two pre-amplifiers for formal review, a Magnetic Silverstone B&R Reference pre-amplifier and a valve pre-amplifier called The Enigma. Both pre-amplifiers were to come at the same time but alas a hiccup at Iain’s end meant I only had one of the pre’s the Silverstone B&R Reference while I had the AirTight for review.

Well hooking this pre-amplifier was somewhat of a revelation as it did match the AirTight much better than anything else I had to hand, though there were a few small easily solved compatibility issues (2)

With the Stereo Knight Silverstone B&R Reference in circuit there was slightly more of everything, more weight and scale, more depth, width and height to images and a better sense of coherence, not something I was aware had been missing before but with the pre in situ the way music was reproduced just seemed to hang together better than when it was not in circuit and the ATM 300 was hooked directly to my Moon Andromeda. Bass was largely unaffected by the presence of the pre except that I felt it now had just a little bit more dynamic shading.

During this period I listened quite a bit to the old reference recording which I use for most of my reviews but I also tried a few new ones to this role, such as the new Esoteric remaster of Utopia’s album POV, which not only is in my opinion the best digital version of this album but also an interesting album from a production poit of view. Todd Rundgren is in my opinion a very talented song writer, musician and some time producer. However quite often his through everything in bar the kitchen sink wall of sound can end up muddy, compressed and somewhat impenetrible . POV falls at times into this later category at times and yet the AirTight even without the Stereo Knight Silverstone pre-amplifier still managed to unravel the thickness of this album’s production and open the music up. However, playing this album with the pre in the system and this album really opened up more.

Playing Mystified the tight, extended bass which propels the song along with the drums, had excellent pace and timing and I found myself tapping my feet along in time with the music. The normally slightly dense nature of this track was much more open than I have heard before and revealed a wide, deep soundstage upon which Todd and the boys played their hearts out. The song was effortlessly musical just flowing along and carrying me to places it has not quite gone in the past and all of this despite the slightly compressed nature of the recording. Once again the AirTight’s trick of not making a meal of recording quality was evident.

Secret Society’s fluid pulsing bass lines were beautifully rendered with excellent non spotlit instrument separation, each musician having his own space in the acoustic but still playing together as a band. The sound of this track and others on the album were quite intoxicating, as the ebb and flow of the music filled my room.

I could of course give you a blow by blow account of how other album tracks were reproduced, but I don’t want to bore you too much by going into how every track I played sounded. However  the bottom line is none of the music I played during this review (once I had optimised things) sounded anything short of very good and quite often was better than that  and I was always able to hear things I had not heard before or if I had I was able to hear them reproduced better. For instance the cymbal strike, decay and shimmer on the track Red Earth (1.30) by Rain Tree Crows of their self titled album had air shimmer and shape I have never heard before and I know this track intimately having used it for assessment and pure listening pleasure since it came out on CD back in 1991.

As I mentioned earlier on in this review I did despite hearing an excellent amplifier feel I was still not quite getting to the very bottom of what it is capable of. There was a bottle neck I felt and despite the Stereo magnetic breaking most of that down I still think there is more to be had from the ATM300 but to do that I believe I will need a matching AirTight pre-amplifier something I don’t have to hand currently  to plumb those extra depths i know instinctively are there.


I will make no bones about this particular review it was frustrating but also at the same time uplifting and exciting in equal measure. It was frustrating in so much that I am sure there is more to hear from this wonderful amplifier but sadly I am unable to do that at the current time. However the results I was able to achieve were still breathtakingly good, especially with it hooked up to the Stereo Knight Magnetic Silverstone B&R Reference pre-amplifier, all be it its high output required me to use attenuators to better match to the ATM 300 input.

This amplifier if carefully matched to the right pre-amplifier and speakers will I feel redefine what a high end valve amplifier can do, especially one that uses 300Bs; a valve type I had yet to hear, before hearing this amplifier, that I particularly liked as most of those were overly warm and somewhat stodgy in the bass. However as they say implementation is everything and in the case of the AirTight ATM 300 Mr. Miura’s has created something very special indeed.

Well done that man.


Source of loan: End owner user.

UK Distributor: Select Audio http://www.selectaudio.co.uk/

Retail price £7200 without valves, £7500 with Electro Harmonix valves.


Self-biased Class-A operation at 300B output stage

3-stage triode amplification for sublimate musicality

DC-driven heater to reduce noise inherent in direct-heated valve

Bias/current meter to check optimum operation of output valve

Damping selector control to create one’s favourite sound

Lavish employment of second-to-none, custom-selected components

Copper-plated chassis to remove magnetic distortion

Attenuator on direct CD input

The Absolute Sound 2007 Editors’ Choice Awards: “The Air Tight ATM 300 is one of the handful of 300B SET amplifiers that lays claim to magical sound extending beyond the midrange. The amp’s airy highs, natural tonality, and low-bass extension defy common perceptions of 300B SETs.”

Valves employed 300B x 2, 5U4G x 1, 12BH7A x 2, 12AU7A (ECC82) x 2

Rated output 8W + 8W (8 homs)

THD less than 1% (6W)

Input sensitivity 230, 300, 450mV

Damping factor 0, 4, 6dB adjustable

Dimensions 430 (W) x 275(D) x 245 (H) mm

Weight 24 kgs

(1) Though I guess the possibility exists with a single source system that perhaps matches better than my Moon Andromeda or Marantz SA7 that that may be a viable option for some but frankly the tiny nature of the left and right level adjusters and markings made it very fiddly to use day to day, for me anyway.

(2) The Silverstone pre-amplifier has a very strong output level and using a mixture of RCA and XLR inputs to the RCA output did not change this so I had to use a set of 6db Rothwell attenuators to give myself a reasonable range of volume control and avoid overload problem.

© Text/Photos Copyright 2011 Adventures in High Fidelity Audio except Album cover art and AirTight ATM 300 promotional picture. In those cases copyright belongs with them.

NB No part or portion of this article may be reproduced or quoted without written permission.

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