Интегральные усилители — Soulnote A-0 ver.2

The A-0 ver.2 is the entry integrated amplifier of Soulnote from Japan, sold as the A-0 VER2 SF in silver and the A-0 VER2 BF in black. Soulnote describes it as an extremely simple configuration, essentially a power amplifier with a selector plus volume adjustment, mirroring the layout of the company's A-3. Its speaker output is deliberately kept low so that audio quality takes priority over power, and the circuit is fully discrete without negative feedback.

Key specs that matter

Rated output is 10 W x 2 into 8 ohm, with distortion of 0.2 percent from 10 Hz to 100 kHz at 3.3 W. Speaker frequency response reaches from 5 Hz to 350 kHz within +0/-1 dB, while Soulnote quotes 115 dB IHF A for noise. A headphone output delivers 3.0 W x 2 into 32 ohm at 0.03 percent distortion, covering 5 Hz to 400 kHz. The pre-out gives 2.0 V at 0.01 percent. Four line inputs are fitted. LINE 1 and 2 are balanced, with 0.66 V sensitivity and 10 kohm impedance in High mode or 4.0 V and 50 kohm in Low mode, while LINE 3 and 4 accept 0.66 V at 5 kohm or 4.2 V at 25 kohm. Total gain is 22 dB in High mode and 8 dB in Low mode. The case is 430 x 109 x 418 mm and weighs 8.0 kg.

Engineering and use context

TO-220 transistors in one push-pull pair form the output section, driven by a four-stage Darlington circuit. Holding the power this low lets Soulnote use the 2SA1930 and 2SC5171 devices, and a newly developed bias circuit brought a marked improvement in signal to noise performance. The balanced inputs stay balanced along the whole signal path with no conversion to single-ended. The gain switch is meant for refined listening at low volume. The top cover is deliberately left unfixed, and a direct mechanical grounding construction places a foot beneath the transformer to lead vibration away. The pre-out has its own High and Low modes and is available on both RCA and XLR connectors, each wired for balanced operation. The line traces back to the original A-0, a tenth-anniversary model that kept the basic concept of the earlier SA1.0 while its non-feedback discrete circuit was rebuilt.

Pairing

Balanced sources such as a Soulnote D/A converter can use LINE 1 or 2 to keep the chain balanced. The pre-out makes it possible to add a larger power amplifier later while keeping the A-0 ver.2 as the control unit.

Alternatives

The Soulnote A-1 is a more powerful integrated model in the Soulnote range, rated at 80 W per channel.