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One of those is incredible microdynamics and low-level resolution which do not exist anywhere in that form. The ATM-300 was no exception. Each disc - and I listened to this beautiful amplifier extensively- was presented with an extremely well-defined soundstage. I am not even talking size (this is a secondary issue with this amplifier whose virtual stage is very large but not blown out of proportion) but how instruments, voices and effects were defined within the soundstage boundaries. The Air Tight positioned them all in a very natural way, slightly soft but not softened, simply not hard. Whether a large church like Missa Criolla with José Carreras or the interior of a recording studio from June Christy’s Something Cool or the artificial effects from the newest Depeche Mode single, in each instance the ability to present the stage as a whole as well as its details in particular - by letting us know what roles they played in the creation of the sound - was truly outstanding.

I think that this characteristic, together with the very liberated sound on a whole is a big reason for the breed’s admiration. It’s hard not to fall for. Despite the mediocre 8-watt output power, the sound can be quite strong and loud. Bass is seemingly limited below 40Hz but amplifiers like the Reimyo clipped far sooner. This limitation probably won’t be audible on high-efficiency widebanders loudspeakers but becomes obvious with loudspeakers like my Harpia. But this amp played really really loud.

Of course I eventually managed to clip the Air Tight but even that was different. Before I get to that, I want to comment on its tonal balance as one is closely related to the other. When I listed 300B amplifiers earlier, I did not mention the Ancient Audio Integra integrated amplifier (a single 300B) and Silver Grand monos (2 paralleled 300B). That’s because they don’t meet one of the criteria related to cult amplifiers. Their power supplies are transistor, not regulated or rectified by tubes. Although the first version of the Polish Silver monos did employ GZ34 tubes rectifiers, designer Jarek Waszczyszyn stopped using them quickly. I witnessed those changes and must say they were beneficial for his amps. Now I shall call upon them because the sound of the Air Tight, especially its tonal balance, reminded me much of them. The four other amplifiers mentioned earlier were far warmer, had a visibly rolled-off top end and a slightly boosted lower midrange. Compared with those, the ATM-300 was much more linear (more about this later) and neutral. Nothing was added hence the vocal range, particularly its lower section, was leaner. At least with the tubes supplied, this amp was also much clearer and less editorializing.

The treble benefited most. Not as resolving as the Grand (no chance of that), it was better differentiated and more colorful than any of the other 300B amp I’ve heard save perhaps for the Reimyo, which managed warmth and resolution in tandem. The ATM-300 placed vocals a bit farther back in the mix than the Reimyo and Ancient Audio. Actually all sounds moved farther behind the loudspeakers. How far back mostly depended on the setting of the damping switch. That changes the output impedance with negative feedback. The higher the damping and thus woofer control, the closer the stage moves and the more palpable the virtual performers become. Output of course reduces accordingly (that’s how higher feedback operates).


This was handy with Rock and strong electronic bass. The trance/dance beats from the Depeche Mode double single Fragile Tension/Hole To Feed had the power they deserve only with NFB. Undoubtedly my 60wpc solid-state Luxman handled all that much better, reached  far lower, had better bass control and differentiation and hence also better timbre. Naturally lovers of 8-watt valve amps know these limitations and learn to live with them as the necessary sacrifice to the 300B.