Усилители мощности моно — Kondo Audio Note Japan Kagura2

The Kagura2 from Kondo Audio Note Japan is a monaural power amplifier built around a parallel single-ended pair of 211 triodes, so a stereo system needs two chassis. The current production version is listed by the maker as the Kagura2 i, and each unit is a very heavy, tall valve amplifier fed by three separate transformers.

Key specs that matter

Rated output is 50 W at 1 kHz with 5 percent THD. Audio Note quotes a frequency range of 10 Hz to 55 kHz, measured at 1 W with the upper limit set at minus 3 dB. There are two inputs, one RCA jack plus one XLR jack, and both present 70 kohm. The XLR input is wired unbalanced with pin 2 as hot, so it is a connector choice rather than a true balanced circuit. Residual noise is below 0.5 mV. The valve complement is two 211 output triodes, two 6SN7, one 12AU7 and four GZ34 rectifiers. Power draw is 270 W, the chassis measures 320 mm wide, 370 mm high and 558 mm deep, and each monoblock weighs 62 kg.

Engineering and use context

The voltage gain stage runs from a 12AU7 into a pair of 6SN7, and two further 6SN7 act as a cathode follower driver for the 211 pair. The three transformers create three supply circuits at four different voltages, namely plus and minus 200 V, plus 450 V and plus 950 V. Kondo fitted newly developed cut-core choke coils and oil capacitors rated at 1000 V in the supply. The voltage amplification sections are built as modules and use silver foil capacitors. The output transformer is wound with pure silver wire and offers 4, 8 and 16 ohm taps, with two of them, 4 and 8 ohm, preset at the factory as the connected outputs. The high supply voltages and the four rectifier valves explain much of the mass and the high consumption, which stays with the amplifier whenever it is switched on.

Pairing

Because the input is unbalanced even on the XLR socket, a line preamplifier fitted with RCA or XLR outputs is suitable, and the 70 kohm load is easy for valve output stages. The factory-set taps cover the usual loudspeaker impedances, and the loudspeaker choice should follow the power limit of a single-ended design. Kondo's own G-1000i line preamplifier provides both RCA and XLR outputs for such a system.

Alternatives

The Kondo Gakuon II is another 211 parallel single-ended monaural amplifier, housed in a smaller 280 x 242 x 525 mm chassis weighing 33 kg.