Airtight ATM-211 single-monaural going strong in new edition
Airtight launched the new 211 single monaural power amplifier ATM-2211. This time, Airtight decided not to use the overall Negative Feedback (NFB) from the secondary side of the output transformer, but to apply a large amount of NFB from the plate of the 211 output tube to the first stage. This is because the sound penetrating power and the energy feeling are emphasized rather than the so-called characteristic improvement. The operating point of each components of the circuit were designed more strict, and increased the output to 32W. ATM-2211 uses fixed bias method and DC ignition for the filament.
For the Ip monitor and bias meter, Airtight installed a large vertical edgewise type for easier viewing and adjustment setting. Replacing 211 output tube is easy as a dial corresponding to both the plate loss 75W type vintage tube 211 that exists separately from the conventional 211/VT-4C plate loss type 211. This time, Airtight used independent power transformers for high-voltage and low-voltage which used to be integral type in past model. In addition, the choke coil, which can be said to be the heart of the single amplifier, is made of layers that do not use the traditional bobbin and are specially made to withstand high voltage.
This choke coil is custom hand-crafted by Japanese craftsmen piece by piece, and it help to realizes a sound stage with good visibility and dynamic low range sound. For the output transformer, Airtight installed high output type made by Hashimoto Electric Co., Ltd., for better response of the low region. The main chassis is AirTight's traditional monocoque construction that controls resonance and keep mechanical strength of the amplifier. A thick pure copper sub-chassis is suspended from the main chassis to support the main amplification board and the power supply section on which the large block capacitor is placed.
The main chassis has a structure that uses a threaded stud where the head of the screw is externally invisible, and this ensure electrical conductivities by pressing the boss itself into the chassis. The thick front panel was machined from a thick Aluminum Block. Loudspeaker terminals made by WBT of Germany are separately equipped for high (8Ω) and low (4Ω) output (16Ω can be selected as a factory set option). The input terminal is equipped with selectable RCA and XLR terminal. When the power is turned on, a built-in timer relay activates and plate voltage is applied with a time difference. $55,000 per pair. ■