Soulnote A-3 Core Stereo Power Amplifier

A-3 Core Stereo Power Amplifier

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A-3 power amplifier stereo power amplifier

Completely separated left and right channel GND

The completely isolated GND technology achieved with the P-3 preamplifier has been applied to the A-3core power amplifier, just as it was with the A-3 integrated amplifier. Ungrounding the chassis of a stereo power amplifier that handles high currents is unprecedented. This unit achieves ungrounding of the power amplifier chassis through a simple non-feedback circuit, optimized artwork design, minimization of high-current loops, elimination of inductance components, and other measures, resulting in the birth of the A-3core stereo power amplifier, which features completely isolated left and right GNDs. The three-dimensional sound field and sense of openness set a new standard for stereo power amplifiers.

Single push-pull output stage

The output stage uses a single push-pull SEPP circuit with TO3 (metal can type) bipolar transistors, the same as the M-3. This achieves smooth music reproduction from the ultra-low to ultra-high frequencies. This heart-stirring music reproduction is the result of a single push-pull circuit that does not destroy the purity of the minute time axis.

4-stage Darlington configuration with ultra-powerful driver and pre-driver

To easily drive the TO3 (metal can type) transistors, ultra-powerful TO3P transistors are used in the driver and even the pre-driver. This ensures perfect current supply all the way to the bottom end, regardless of hfe fluctuations at high currents, resulting in both deep expressiveness and an exciting groove.

Copper bus bar/heat sink

The main heatsink is a lightweight, compact copper heatsink. This heatsink also serves as the power busbar for the TO3 (metal can type) transistor. The TO3 transistor terminals pass through the busbar and are mounted directly to the PCB directly below. This eliminates the wiring that is a drawback of TO3 transistors, eliminating instability caused by inductance while also eliminating the degradation in sound quality that can occur when the insulating sheet damps the device. Furthermore, the heatsink's physical isolation from the chassis provides a sense of freedom and clarity, significantly improving sound quality. Furthermore, the A-3core's busbar heatsink also serves as a structural component, connecting the power supply board and amplifier board to form a block. This heatsink truly kills four birds with one stone.

New Type-R Circuit:

For voltage amplification, we have developed a new high-gain, single-stage, ground-to-ground amplifier, Type-R, circuit. Naturally, we have generously used naked foil resistors for all resistors involved in amplifier operation.

GND anchor

The left and right channel GNDs are grounded to the left and right side metals, which are insulated with ceramic washers. A special housing structure is used that functions as a GND anchor, achieving a high level of both openness and low-end grip.

Super powerful power transformer

Two 700VA non-impregnated toroidal power transformers are used for the mains, one on each side. Three power transformers, including a control power transformer, are packed into a single housing. All are mounted vertically so that the magnetic field lines are parallel to the circuit board.

High-speed non-feedback power supply

The rectifier capacitors are specially selected, with a mere 470μF of high-voltage, small-capacity, low-magnification foil filter capacitor. By optimizing the capacitance through the number of capacitors used and reducing the load on the power transformer, the effective regulation of the ultra-powerful power transformer is further improved. The rectifier diodes are SiC diodes with the latest specifications, featuring enhanced inrush current tolerance.

This is the most powerful and high-speed power supply configuration imaginable. Furthermore, two large, high-quality power relays are independently positioned as power switches for the two main power transformers, each with its own high-current contact. Having separate power switches for each power transformer is extremely important for sound quality. The power switch on the front panel is dedicated to the control sub-transformer.

Free-standing structure

The amplifier block, terminals, AC inlet, top cover, and bottom cover are all floating and unfixed. The amplifier block in particular uses a three-point sliding structure with titanium sliders. This allows it to escape harmful vibrations from the power transformer while also releasing its own inherent vibrations.

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