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Soulnote A-2
Integrated Amplifier
PREMIUM SILVER / PREMIUM BLACK
Every SOULNOTE technique has been lavishly incorporated into the current culmination of our perfectly balanced non-NFB technology. This integrated amplifier is loaded with a variety of monaural drive and power amplifier modes, like the new BTL/bi-amp setting.
Perfectly balanced, discrete non-NFB circuit
SOULNOTE's original perfectly balanced non-NFB circuits have been fully optimized and incorporated to give sound quality the highest priority. Voltage feedback has been completely eliminated in the output stage, the voltage amplification stage, and the power supply circuits. Because of their impact on the sound, circuits of DC servo and current mirror have been eliminated, while both the constant current and bias circuits in the voltage amplification stage employ simple circuitry layouts that only use constant current and voltage elements (2SK209 and LEDs, respectively) carefully selected for utmost sound quality. The voltage amplification stage is perfectly balanced all the way through the emitter follower output. A-2 is designed to reproduce music in a dynamic, open, clear, and soulful way.
Relay-switching balanced attenuator
The volume adjustment is not controlled by electronics or a rotary-type slider volume, but instead incorporates SOULNOTE's original relays in a balanced attenuator system that switches high-precision resistors. This dramatically increases clarity and allows the sound image to emerge in three dimensions. It also significantly improves quality in a low volume level without worrying about gang errors.
An ideal construction
The input signal line has been minimized by concentrating the input terminals, input selectors, volume, and the non-NFB voltage amplification stage onto a single multi-layered board. The board does not use even a single shield or filter that could negatively impact the sound in order to eliminate every factor that reduces sound quality, such as the effects of vibration from connecting cables, inductance components, radiation noise, etc. This ideal construction has been achieved thanks to the relay-switching balanced attenuator.
4-layer board with 70μ thick copper foil
Composed of the output stage and the main power supply, the power block features an inner layer of 70μ thick copper foil substrate inner layer plane as the power supply busbar and thus minimizes high current loops in the commutating capacitor > output transistor > loudspeakers + terminals > loudspeaker terminals > commutating capacitor cycle. Eliminating inductance components in high current lines creates outstanding frequency characteristics and stability.
Direct connection
Connectors have been eliminated in the power supply as well as the signal lines, and cables are instead soldered directly to the boards for direct connections.
Chimney-type heat sink
The heat sink is a newly developed chimney type that pursues a shape with high cooling efficiency and low intrinsic vibration.
Powerful power supply
The power supply utilizes a 600 VA bifilar wound toroidal transformer, the most powerful in SOULNOTE's history. Commutating current loops have been minimized by placing ± independent rectifying circuits from the fast recovery diode close to the transformer winding. The commutating capacitor is supplied by ELNA specially developed for SOULNOTE and selected for its sound quality. Connecting multiple capacitors of small size in parallel helps adjust and optimize high frequency characteristics and overall capacitance.
4 parallel high-speed output transistors
The final stage is composed of 4 high-speed transistors (2SC2837/2SA1186) with low Cob and high FT connected in parallel. This combines with the strong non-NFB power supply to provide generous loudspeaker driving power.
Output transistor selection
The output transistors have been selected and paired by using a specially designed device that measures the Vbe current value while avoiding any influence from rising temperatures in the output transistors. Perfectly aligning the 4 parallel current transistors creates abundant loudspeaker driving power and clear, precise sonic reproduction.
4-step Darlington circuit
High-frequency transistors create a 4-step Darlington configuration to drive the final transistors completely, thereby optimizing the amount of each current. This produces plentiful drive power for every loudspeaker.
Housing design that prioritizes sound quality
A spike grounds the power supply transformer directly, and while combining the spikes with uneven cross-sectional aluminium panels to control resonance has increased rigidity, the aluminum panels are not directly bonded in order to eliminate unwanted resonance. The top cover, which has a particularly large influence on sound quality, features a dual-component construction that joins the base plate and the aluminum panels at three points so that they do not dampen each other. By grounding it at three points without fixing it to the aluminum portions of the housing itself, this design succeeds in keeping the balance of sound while still keeping it expansive.
Single non-NFB differential BTL circuit
The conventional BTL monaural principle that uses the left and right channels of the stereo amplifier in reverse phases can produce powerful sound quality, but the sound impression tends to blur with sounds tending to clump together because of the effects from GND lines or matching two amplifiers. The BTL monaural mode in the A-2, therefore, adopts a new approach that partitions the differential output of one non-NFB differential amplifier each for the left and right final stage. This creates an expansive sound with vigorous, yet delicate BTL driving.
Two types of monaural modes
In addition to BTL monaural mode, the bi-amp monaural mode can also be selected to distribute the monaural input to the left and right channels.
Power amplifier mode
The power amp mode interrupts the power supply to the microcomputer and bypasses the selector and volume. This increases the SN ratio. XLR and RCA input can also be selected in this mode.
Select from six possible use cases
The following six usage options are available.
- Stereo pre-main amplifier
- BTL monaural pre-main amplifier
- Bi-amp monaural pre-main amplifier
- Stereo power amplifier
- BTL monaural power amplifier
- Bi-amp monaural power amplifier
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Soulnote A-2 — a refined, analogue-first integrated amplifier
The Soulnote A-2 is a purpose-built, analogue-only integrated that champions musical immediacy and refined tonal balance. Reviewers at HiFi News, hi-fi+ and The Ear highlight its velvety midrange, articulate treble and nimble dynamics that favour timing and groove. The amp pairs a substantial power supply and Sanken output devices with a relay-switched balanced attenuator for precise level control and excellent channel balance. Imaging is wide and holographic, with convincing depth and instrument placement, while dynamics remain energetic without sounding aggressive. Built from thick aluminium panels around a 600VA toroidal transformer, the A-2 is aimed at listeners who prioritise musical clarity—classical, jazz, acoustic and vinyl fans will appreciate its insight—and offers high-end execution and performance for its price point.
Pros
- Refined, musical presentation with clear, velvety mids and articulate treble—allows recordings to breathe without adding artificial coloration.
- Exceptional imaging and soundstage depth—wide, holographic presentation with well-focused centre images and convincing instrument placement.
- Robust engineering and high-quality parts—600VA toroidal PSU, pair-matched Sanken transistors and solid aluminium chassis deliver trustworthy build and low distortion.
- Flexible operating modes and healthy power headroom—configurable as integrated, power amp, bridged (BTL) or bi-amp, giving versatility for different system roles.
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Cons
- Deliberately minimal feature set—no DAC, phono stage, digital inputs or network streaming, which limits out-of-the-box connectivity for modern systems.
- Control ergonomics are functional but coarse—relay-stepped volume offers 35 steps (~2dB increments) and the remote/IR can feel restrictive for fine adjustment.
- Bass emphasis favors shape and timing over brute slam—excellent extension and control but not aimed at listeners seeking ‘bone‑crunching’ low‑end grip.
- Minor mechanical quirks reported—intentional loose vents can rattle and a faint transformer buzz may be audible close to the chassis.
Sound Quality
91/100
Dynamics
90/100
The A-2's Class-AB push-pull design with substantial power (100W/8ohm; 200W/4ohm) is repeatedly described as nimble, punchy and able to handle dynamic extremes without strain (Hi-Fi+, The Ear). Reviewers mention strong timing, groove and headroom for its class although not 'preposterously powerful', so dynamics earn an excellent but not reference-level score.
Soundstage Imaging
92/100
Multiple reviewers highlight wide, holographic imaging and very good depth and focus — with convincing instrument placement and a big, stable soundstage on varied material (Hi-Fi+, HiFi News, The Ear). The A-2's ability to present a three-dimensional picture and focused centre images supports a high score for imaging.
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Build Quality
92/100
Build is described as excellent and substantial (20kg chassis, thick aluminium panels) with a 600VA toroidal transformer and pair-matched Sanken output transistors, and careful relay-switched balanced volume control (HiFi News, The Ear, Hi-Fi+). Minor quirk noted (intentionally loose vents that can rattle) but overall construction and component choices are high-end and robust.
Features Connectivity
83/100
Soulnote deliberately keeps the A-2 analogue-only with three single-ended RCAs and three balanced XLR inputs plus a relay-based balanced attenuator and remote; there is no DAC, phono stage, headphone output or network streaming (HiFi News, The Ear, Hi-Fi+). That focused approach yields a modest feature score above the minimal baseline but well short of fully-featured modern integrateds.
Value for Money
90/100
Reviewers repeatedly state the A-2 offers strong musical performance for its asking price and is 'extremely well executed for the money' (The Ear, HiFi News notes a UK price of ~£6,300). Given consistent praise that it delivers exceptional musical insight and construction relative to peers, it earns a justified-premium rating.
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