Усилители мощности моно — Soulnote M-3

The M-3 is a monoblock power amplifier made by Soulnote in Japan and offered in silver as the M-3SE and in black as the M-3BE. Its output stage is a single push-pull pair with no feedback loop in any stage, built on industrial-grade metal can transistors chosen for low Cob and large current capacity. Soulnote still lists it in its amplifier range next to the later M-3X.

Key specs that matter

Maximum output is 160 W into 4 ohm. Distortion is 0.1% at 1 W and the response extends from 2 Hz to 200 kHz within 1 dB. Input sensitivity is 2 V with an input impedance of 25 kohm, and gain is 22 dB. Consumption is 110 W at full load and 36 W with no signal, from a 230 V 50 Hz supply in the European version. The chassis measures 340 x 257 x 512 mm and weighs 31 kg. A special speaker cable, a dedicated rack, a power cable and a setting plate come in the box.

Engineering and use context

Soulnote holds that a single push-pull output avoids blurring in the time domain, but such a stage usually offers limited current, so the M-3 uses large can transistors driven through four Darlington stages. The driver stage uses the output transistors of the Soulnote A-2 integrated amplifier. Small copper plate heat sinks double as bus bars that power the output devices, whose leads pass through them straight to the board, so no wiring or insulating sheets sit between transistor and circuit. The heat sinks are also isolated from the chassis. Voltage gain comes from a new Type-R circuit of four bipolar transistors and ten resistors, a topology Soulnote compares to single-ended valve amplifiers. There is one XLR input and one pair of speaker terminals, no selector, no attenuator and no microcontroller - the power switch is the only control. Power comes from a 1600 VA toroidal transformer without epoxy filling, mounted upright on the front panel so leakage flux runs parallel to the boards and hung on titanium washers above a spike. Filtering uses 470 uF foil capacitors in parallel, and rectification uses SiC diodes. The amplifier section is housed in a container physically apart from the main body, and each rests on three spikes, six in total.

Pairing

With only a balanced input and no level control, the M-3 has to be driven by a line stage that has balanced outputs, for example the Soulnote P-3. Two units are required for stereo, and its fixed gain sets how much output the preamplifier must deliver to reach full power.

Alternatives

The Soulnote M-3X is the other monoblock in the range, pairing two matched can transistors per side for 240 W into 2.7 ohm in the same case size.