About 20 years have passed since the launch of the ATM-211 single-monaural power amplifier using 211 tube, which has been well received since its launch in 2001. Since then, we launched 211 push-pull monaural power amplifier ATM-3211, which has become a turning point for the Airtight brand as well as SET ATM-300R. At an eve of 35 years anniversary as AirTight, we will launch the new 211 single monaural power amplifier ATM-2211.
This time, we 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, we 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, we 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, we 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. This contributes to the protection of the output tube when the power is turned on and the longer life of the smoothing capacitors in the power supply section. As the 211 tube operates at very high voltage, we have carefully selected parts to withstand high voltage and long-term use.
Please enjoy the sound full of energy with the transparency of the next-generation 211 single, ATM-2211.