Усилители мощности стерео — Soulnote A-3core

Soulnote of Japan builds the A-3 Core as the two-channel power amplifier of its Series 3 range. It is derived from the A-3 integrated amplifier, with the control section removed so that the circuit is devoted purely to power amplification, and it is sold in silver (A-3CORE SE) or black (A-3CORE BE).

Key specs that matter

Rated output is 120 W per channel into 4 ohm. Total harmonic distortion is quoted at 0.27% at 1 W into 8 ohm, and the frequency response runs from 2 Hz to 200 kHz within 3 dB under the same 1 W, 8 ohm condition. Input sensitivity is 480 mV with an input impedance of 24 kilohm, and maximum gain is 33 dB. The amplifier runs on 230 V AC at 50 Hz and consumes 180 W in operation and 86 W at idle. The case is 454 mm wide, 189 mm high and 435 mm deep, and the amplifier weighs 29 kg. A spike board, spikes, a spacer for floating the spike board and a power cable come in the box.

Engineering and use context

The distortion figure reflects a deliberate choice - the voltage amplification is a fully balanced topology with no negative feedback, built on a newly developed high-gain-to-GND single-stage Type-R circuit with naked foil resistors. Each output is a single push-pull SEPP stage using one TO3 metal can bipolar transistor per half, driven through a four-stage Darlington arrangement with a strong driver and pre-driver in TO3P packages to supply the current. Instead of a conventional heat sink, a light, compact copper plate acts as both heat sink and bus bar, removing wiring inductance and staying physically independent of the chassis. Soulnote keeps the left and right ground paths fully apart and the enclosure ungrounded, using the simple non-NFB circuits, careful board artwork and short high-current loops. Power comes from two 700 VA unimpregnated toroidal transformers, one per channel and mounted vertically, plus a separate transformer for the control system. Filtering uses deliberately small 470 uF high-voltage foil capacitors and current-generation SiC diodes.

Pairing

With its high gain and sensitivity, the A-3 Core reaches full output from a modest line level, so it suits a preamplifier or a source with its own volume control. Its balanced input stage makes a balanced preamplifier connection the natural choice, and the low-impedance rating shows it is intended for loudspeakers that dip in impedance as well as easier loads.

Alternatives

Soulnote has no other stereo power amplifier.