Soulnote A-3 Core Stereo Power Amplifier
The A-3 Core is the stereo power amplifier from the 3 Series, essentially it is an A3 integrated amplifier with the pre-amp section removed.
As with all 3 Series components the A-3 Core is available in either Premium Silver or Premium Black.
Build quality and fit/finish is to the same high standard as the other Series 3 products, it really is an exemplary looking design.
From Soulnote……
Complete separation of left and right channel GNDs
The GND separation technology incorporated in the P-3 pre-amplifier is applied to the A-3 Core power amplifier as well as the A-3 integrated amplifier. There is no precedent for GND non-grounding in stereo power amplifiers handling high currents. A-3 Core achieves power amplifier enclosure ungrounding through simple non-NFB circuits, optimized artwork design, minimization of high current loops, elimination of inductance components, and other factors. This led to the birth of the stereo power amplifier A-3 Core with completely separated left and right GND. The three-dimensional sound field space and spaciousness are the new frontiers of stereo power amplifier.
Single push-pull output stage
The output stage uses a single push-pull SEPP circuit with a TO3(Metal CAN-type) bipolar transistor as used in the M-3. It realizes blur-free music reproduction from ultra-low to super-high frequencies. The heart-stirring music reproduction is the result of the single push-pull that does not break the micro time axis purity
4-stage Darlington configuration with super-powerful driver and pre-driver
To drive the TO3(Metal CAN-type) transistor easily, ultra-powerful TO3P transistors are used in the driver as well as in the pre-driver. Ensuring perfect current supply all the way to the bottom end without regard to hfe fluctuation at high currents makes it possible to achieve both deep expressiveness and an exciting groove.
Copper bus bar heat sink
A lightweight, compact copper plate is used as the main heat sink. This heat sink also serves as a bus bar for supplying power to the TO3(Metal CAN-type) transistor, and the terminals of the TO3 transistor penetrate the bus bar and are mounted directly on the board underneath. This eliminates wiring, which is a drawback of the TO3 transistor, and helps overcome instability caused by the inductance component, while at the same time avoiding sound quality degradation caused by the insulation sheet dumping on the device. The sound quality effect is also extremely impressive, with a sense of freedom and transparency due to the physical independence of the heat sink from the chassis. Furthermore, in the A-3 Core, the power supply board and amplifier board are connected by a bus bar heat sink, which also serves as a structural component to form a block. It is truly a “four birds with one stone” heat sink.
New Type-R circuit, fully balanced non-NFB
For voltage amplification, a newly developed high-gain-to-GND single-stage Type-R circuit is adopted. Naked foil resistors are used generously for all resistors involved in amplifier operation.
The GND of the left and right channel power supply units is grounded to the left and right-side metal insulated with ceramic washers, a special enclosure construction that acts as a GND anchor. A sense of openness and low-end grip is achieved at a high level.
Super-strong power transformer
2x 700VA unimpregnated toroidal power transformers are used for the power amplification, to the left and right. In addition, three power transformers, including the control system power transformer, are packed into one enclosure. They are all mounted vertically so that the magnetic field lines are parallel to the board.
High-speed non-NFB power supply
For the rectifying capacitor, a specially selected high withstand voltage small capacitance low magnification foil filter capacitor of only 470uF is used. To optimize the capacity, the number of units used was determined and the load on the power transformer was reduced. This further improved the real regulation of the ultra-powerful power transformer. For the rectifier diodes, SiC diodes of the latest specifications with enhanced allowable inrush current are used. This is the most powerful and high-speed power supply configuration ever considered. In addition, two large power relays with excellent sound quality are used independently and without fixing as power switches for the two main power transformer. Independent power switch for each power transformer, which is a high current contact point, is extremely crucial for sound quality.In addition, the power switch on the front panel is dedicated to the control system sub-transformer.
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 sliders. While escaping from the harmful vibration of the power transformer, it also releases its own intrinsic vibration.
