Интегральные усилители — Kondo Audio Note Japan Overture PM-2i

The Overture PM-2i is the single integrated amplifier in the current range of Kondo Audio Note Japan, a Tokyo company otherwise known for separate valve preamplifiers, phono stages and power amplifiers. It is a revised version of the earlier Overture, and Kondo describes the aim as pairing the output of EL34 pentodes with qualities it associates with triodes. The redesign touched the output transformer, the circuit values, the power supply and the signal capacitors.

Key specs that matter

This is an EL34 push-pull stereo design rated at 32 W per channel at 1 kHz and 1.5 percent THD. The tube complement is four EL34, two 12BH7 and two 6072. Frequency response is 10 Hz to 90 kHz within +0 and -3 dB at 1 W. There are four pairs of unbalanced RCA inputs, each presenting 50 kohm, and the speaker outputs have separate 4 ohm and 8 ohm taps. Residual noise is below 0.5 mV. The chassis measures 438 x 201 x 409 mm without protrusions, weighs 26 kg and draws 180 W from the mains.

Engineering and use context

The new output transformer carries a third winding used only for the feedback loop, and the amount of feedback was recalculated so that just 3 dB of global NFB is applied. The output tubes run in ultralinear connection, a halfway point between pentode and triode operation, and are biased by a newly designed constant current circuit that Kondo calls CCB. The first and driver stages are direct-coupled, so no coupling capacitor sits between them. Where capacitors remain in the signal path, including the output stage, they are Kondo's own silver foil types, which were upgraded for this version. In the power supply, the separation between the two channels was improved, and resistor and capacitor values across the circuit were re-tuned. Kondo notes that the amplifier needs about 15 minutes of warm-up before it reaches its rated performance, so it is best switched on well before listening begins.

Pairing

With moderate power from a low-feedback valve stage, the PM-2i is suited to loudspeakers of moderate to high efficiency, and the tap selection lets the output transformer match the nominal impedance of the speaker. All four inputs are line level and single-ended, so records can only be played through an outboard phono amplifier, and a moving-coil cartridge also needs a step-up device before it. Kondo's own GE-series phono amplifiers and SFz transformer fill those roles, and the company also offers SPs-2.7 speaker cable and Theme 31 and Theme 41 interconnects wound with silver conductors. Digital sources connect through an outboard DAC with RCA outputs.

Alternatives

The Kondo ONGAKU is a 211 single-ended stereo amplifier with four RCA inputs and volume control, rated at 27 W per channel at 5 percent THD.