Предусилители — Air Tight ATC-7

The ATC-7 is a stereo valve line control preamplifier made by A&M Limited in Japan under the Air Tight name, and the maker calls it its most advanced volume control system so far. The project was in development from 2018, and the preamplifier made its North American debut in 2023. List prices include EUR 38,500 in Europe with VAT and AUD 52,000 in Australia.

Key specs that matter

Five line inputs are provided - three pairs of RCA and two pairs of XLR, with the XLR sockets wired unbalanced - and there are two pairs of RCA outputs, with an XLR output available as an option. Input impedance is 100 kohm and line gain is 19 dB. THD is 0.02 percent at 1 V and 1 kHz. Maximum output is 20 V into a 100 kohm load at 1 percent THD. Frequency response spans 10 Hz to 100 kHz within minus 1 dB. Power consumption is 50 VA. The chassis is 400 mm wide, 350 mm deep including the controls and 145 mm high, and it weighs 13.5 kg.

Engineering and use context

The signal path uses two 12AX7 and two 12AU7 valves, hand-wired point to point without printed circuit boards. The power section has two transformers with low leakage flux, one for the high-voltage supply and one for low voltages. A fully regulated supply includes a choke coil suited to the audio band and large film capacitors in the decoupling circuit, so there are no electrolytic capacitors in either the signal or decoupling paths. The housing mixes Bakelite and steel for rigidity and control of valve microphony. The amplifying circuit sits in a black chrome-plated inner chassis suspended on a purpose-made Bakelite bar that keeps it electrically isolated. The front panel is 15 mm thick aluminium, cut on an NC lathe and anodised. Volume is set by an ALPS RK-501 mechanism and inputs are chosen with a mechanical rotary selector. Further rotary switches handle a bass compensator and a gain trim, and the knurled knobs make settings easy to repeat. The controls follow a classic layout, and the design relies on physical switches rather than digital menus.

Pairing

The high output ceiling leaves plenty of margin for power amplifiers of low sensitivity, valve or transistor. Because the XLR inputs are not balanced internally, sources with balanced outputs work through them but gain no common-mode rejection. The single-ended outputs suit power amplifiers with RCA inputs, such as most Air Tight valve models.

Alternatives

The Air Tight ATC-5S is another valve line preamplifier listed in the maker's current range.