Review: Air Tight ATM-3 Tube amp

Category: Amplifiers

Air-Tight ATM-3 Mono Block Triode Amplifiers
When I came home and saw the Air-Tight ATM-3's two boxes, their size and weight surprised me. These were as big as my Plinius SA-102 boxes with a weight of 55 lbs. I unpacked the amps and set them on the floor. They started building the ATM-3 in 1991 with an original price of $ 12,800. They have now stopped them and can be found used for around $ 4000-4500.
My first impression was they were just like the tube amps from the sixties. A brushed aluminum face plate, a couple buttons and a meter were all that graced the surface. Behind the face plate are (6) 6CA7 output tubes, (1) 12AX7 and (1) 12AU7, enclosed in a thin, inferior feeling black steel casing with holes for ventilation. I wondered if the thin metal could add some noise (ringing) to the tubes through vibration. I am left wondering why they still use this type of enclosure. They rated the output at 55W Triode and 110W Pentode. They provide a selector switch to choose between the two modes of operation. I used the Triode mode for my audition. The back side of each amp has a single RCA input and two screw type speaker binding posts. The hole in the post is not large enough to accept my banana fittings, so I had to find my WTB spades to adapt the speaker cables. To my disappointment only a fixed power cord is available, precluding one of my preferred tuning tweaks.
After setting the amps on the Neuance shelves used by my two Plinius SA-102 amps I connecting them into the system. After letting them warm up for about four hours before my first listen. My initial impressions were mixed, overall the sound was smooth, good deep base, great depth but lacking in PraT and detail compared with what I am familiar. I left the amps running for the next two weeks before any critical listening. I started my evaluation with a few well-known current favorites, Dead Can Dance "Into the Labyrinth," Patricia Barber's new "Verse," Kasey Chambers "Barricades and Brickwalls," Lucinda Williams "Car Wheels on a Gravel Road," Nora Jones "Come Away With Me," Patricia Barber "Modern Cool" SACD, Alison Kraus "New Favorites" SACD, Duke Ellington "Blues in Orbit" SACD, and "Natures Realm" Philadelphia Orchestra SACD.
They impressed me with their depth and power in the bass. Not quite as tight as the Plinius nor do they provide the same degree of texture. However, they had all the power and punch to which I am familiar. The midrange was as smooth, liquid and effortless as any amp I have heard. This could be a great thing with certain set-ups, but for me it became problematic. Patricia Barber's voice was gorgeous, as rich and smooth as imaginable. I have seen Patricia often in person, and her voice is simply not this liquid. Her voice is dark and biting, like a strong cup of coffee. The Air-Tights made it a thick chocolate with a smooth creamy caramel. If I had never heard Patricia on my system or in person, I would say this was great, but as it was it is simply not real. Two of my favorite women, Kasey Chambers and Lucinda Williams and the male voice on Dead Can Dance has a lot in common in their vocal style. They have a great deal of grain and texture in their voices, filled with expression and emotion. I enjoy these singers because I can feel their souls, they extend their raw emotion through their raspy, throaty voices. An infinite palate of color, texture and sensation is expressed through their voices, giving me a window into their souls. The Air-Tight simply glosses over all of this, and they are not able to delineate this fine level of detail. Again had I not heard these women in person, and through my system, I would be running around praising their smooth liquid voices. The problem is smooth and liquid would never be the way one would describe a live performance from either one of them. On Patricia Barber's "Verse" and "Modern Cool" and Duke Ellington's "Blues in Orbit" there are passages of trumpets. In real life and with my system the trumpet is biting, brassy and harsh. The Air-Tights made them warm, smooth and harmonious. Although the treble on the amps is closer to natural, they still were a bit edgy at the very top. This was the type of energy that makes your ears ring a bit, but not so much that it was offensive. Removing the metal back improved this some, but it remained an annoyance. I am sure cables and footers could solve this issue with the proper diligence. The depth of the presentation was impressive but very different from my system and it took me awhile to get a grip on it. My system puts the front/ middle performer about 5' behind the speaker plane, and with a small ensemble the stage is 10-15 feet deep. With the Air-Tights the front was 10-15 feet back and the back of the stage was at least 50' away. The rear performer would often change positions based on who played the lowest note. If the drum were lower than the bass player, the drummer was in back. If the bass player was lower, he became the back player. This was not overly noticeable, but once I saw it I became obsessed with it. The most serious issue for me was the PraT (Pace, Rhythm and Tempo). Plinius are an extremely fast amp and they have an energy that brings excitement and life to the music. The Air-Tight's were unable to keep pace (so to speak) They were simply unable to produce the life and energy I am familiar. I found myself uninterested in music I love and enjoy on a continuing basis.
So overall, with my system these amps left disappointed me. Now consider that my system consists of Dunlavy IVa speakers, large full-bodied speakers. I believe these may not be the best fit for tube equipment. My impression was with a different speaker the whole picture might change. If for instance I had tried Martin Logan or Megapan with their great transparency and speed, or a tighter cone speaker like Meridian or Theil, I might expect to hear better performance. This is strictly a guess on my part. I already use one of the quickest and most transparent cables (Valhalla) and pre-amp (Placette), leaving the question of how a speaker would alter this annoyance as strict conjecture.
For my tastes, this amp is simply not to the standard of other amps within this price range. If however your looking for the smooth, liquid, colored experience, I would test them out. When I went back to my Plinius amps, it took no time for me to settle back in. I missed my Plinius while this three-week period was happening, I am happy to be back!