Предусилители — Air Tight ATC-6

The ATC-6 is a tube line stage made by the Japanese company Air Tight, and it is the third line stage model in the company's history. It replaces the ATC-3, which was released in 1998, and it keeps the basic circuit of an earlier Air Tight preamplifier while adding a newly developed power supply. Air Tight builds it entirely by hand at its factory in Osaka, using selected parts sourced from Japan, the USA and Europe. The company presents it as a unit focused on essential functions rather than on a long feature list, with digital sources such as CD and streaming in mind.

Key specs that matter

Two 12AT7 double triodes do the amplification, with a JJ valve in the first stage and an EH valve in the second. Five line inputs are fitted as standard - three RCA and two XLR - and the XLR sockets are wired unbalanced (pin 1 ground, pin 2 hot, pin 3 cold). At the factory the input sockets can be set to any combination, and the two RCA outputs can be changed to unbalanced XLR on order. Input impedance is 100 kohm and gain is 18 dB. The line stage delivers up to 20 V into a 100 kohm load at 1% distortion, and distortion is 0.02% at 1 V and 1 kHz. Frequency response is 20 Hz to 100 kHz at minus 1 dB. The chassis is 400 mm wide, 290 mm deep and 90 mm high, the unit weighs 8.3 kg, and power consumption is 50 VA.

Engineering and use context

Controls cover volume, balance and a mute switch, plus a selector with three playback modes - stereo, mono taking the left channel to both outputs (L+L), and mono summing left and right (L+R). The volume pot is an Alps RK-501 customised for Air Tight, fitted as standard. The outer case is a monocoque made of 1.6 mm carbon steel, and the inner chassis that carries the circuitry hangs from the ceiling of that case to control resonance. Left and right channel boards are mounted back to back symmetrically and are fully separated by a 1.6 mm copper plate. The valves were chosen for the lowest microphonic noise, and the new power supply circuit is meant to give the flat amplifier stage clean and stable current.

Pairing

The ATC-6 needs a load of at least 47 kohm, and Air Tight recommends 100 kohm, so it suits power amplifiers with high input impedance, for example the ATM-2211 mono amplifiers or the stereo ATM-1S from the Air Tight range. All inputs accept line level only, so turntable owners add a phono preamplifier, for instance the ATE-3011 from the same maker.

Alternatives

The Air Tight ATC-5s is the third-generation preamplifier whose basic circuit design the ATC-6 was built upon.