"The midrange is where tube magic happens and where the 300B kicks butt. Instrumental timbres were reproduced with exceptional transient and tonal fidelity to the real thing. But it wasn’t just about accuracy and detail resolution. The music flowed with passion, dramatic flair, kinetic drive, and glorious harmonic textures that put other SET amps to shame. Stringed instruments from violin to double bass sang with a lyrical tone. Female vocals were tonally spot on and blossomed from soft to loud with realistic dynamic nuance".- Dick Olsher

https://www.theabsolutesound.com/articles/air-tight-atm-300r-power-amplifier/


The output tubes are a single 300B per channel, specified to output 9W each. Distinctively, the ATM 300R uses global feedback, but tapped from the primary rather than secondary side of each channel's output transformer. AD heard from the Air Tight amp "startling … details of musical nuance," "lusciously textured and colorful" strings and woodwinds, "realistic force" in its reproduction of timpani, and the ability to sound surprisingly big. He also made special mention of the ATM 300R's way with orchestral double-basses, noting their "depth and power, and far greater clarity of pitch than I've heard through any other 300B amplifier, bar none."

https://www.stereophile.com/content/recommended-components-2022-edition-two-channel-power-amplifiers