New A-3 Core Power Amplifier

May 20, 2024

Soulnote electronics have released some technical details of their new A-3 Core. This is a new power amp, borrowing heavily from the development of Soulnote’s flagship M-3 monoblock power amps and the more recent A-3 Integrated amplifier. As you can imagine a number of technical issues had to be solved to squeeze two large monoblocks into the smaller space, without sacrificing sound quality.

We think this will be another amazing product from Soulnote, with chief engineer Hideki Kato’s thorough, detailed approach, allied to his real intuition, guiding the company’s research and development.

Key features

Complete separation of left and right channel ground – The ground separation technology incorporated in the P-3 pre-amplifier and A-3 Integrated is applied to this model with a power amplification circuit.

Single push-pull output stage – The output stages uses a single push-pull SEPP circuit with a T03 can-type bipolar transistors as used in the M-3 monoblock. It realises blur free music reproduction from the ultra-low to super high frequencies, preserving the precious micro time axis.

4-stage Darlington configuration with super-powerful driver and pre-driver – To drive the CAN type transistor easily, an ultra-powerful TO3P type transistor is used in the driver as well as in the pre-driver. This ensures perfect current supply all the way to the low frequencies.

New Type-R circuit, fully balanced non-NFB – For voltage amplification, a newly developed high-gain to GND single stage Type-R circuit is used.

Ground anchor – The ground of the left and right channel power supply units are grounded to the left and right side, insulated with ceramic washers, into a special enclosure which acts as a ground anchor.

Powerful transformers – Two 700VA toroidal power transformers are used for the power amplification. In addition, a third power transformer supplies the control and ancillary functions. They are all mounted vertically so that the magnetic field lines are parallel to the board.

High-speed non-NFB power supply – The rectifying capacitors are specially selected high tolerance, low capacitance and low magnification, foil filter type of 470 uF each. The number of capacitors was carefully optimised for sound quality and transformer load, further improving regulation. The rectifier diodes used are of the SiC type, with the latest specifications and improved voltage surge properties. This is the most powerful and high-speed power supply configuration we have ever produced. In addition, two large power relays, carefully selected for their sound quality, are used independently as power switches for the two main transformers.

Copper busbar heat sink – A lightweight compact copper plate is used as the main heat sink, serving as a bus bar for power to the T03(Metal CAN-type) transistors, the terminals of which pass through the busbar and are mounted directly to the board beneath. This eliminates wiring, which is a drawback of the T03 transistor, and helps overcome instability caused by inductance, and avoids sound quality degradation caused by insulation damping the structure. Furthermore the heat sink is physically independent of the chassis, resulting in a massive sense of freedom and transparency in sound quality.

Unfixed structure – The amplifier block, terminals, AC inlet, top cover and bottom cover are all unfixed. In particular the amplifier block uses a three-point lateral sliding structure with titanium pivots.