Integrated Amplifiers

Soulnote’s A-2, available for £6300 in silver or black, is an integrated amplifier with an air of the ‘old skool’ about it. No network or digital connectivity, just analogue all the way, and only line-level too, as the Japanese manufacturer prefers to keep its phono stages separate. There’s no form of system control (ie, 12V triggers), and the user experience is very much plug-in-and-play, aided by an elegant remote and even simpler front-panel display.

But there is more to this amplifier than meets the eye. Firstly, the A-2 can be run as a power amp, bypassing its internal logic, volume relays and source circuitry. Secondly, it is configurable as a mono integrated or power amp, either in bridged (BTL) or bi-amp modes, the second of these splitting a single-channel input across the A-2’s L/R output. This gives six different applications in total, although there’s no option to use it solely as a preamplifier.

Soulnote is headquartered in Kanagawa, Japan, and currently has three product lines. The A-2 is from its Series 2, positioned between the entry-level Series 1 and flagship Series 3. Somewhat unusually, it’s the marque’s flagship range that offers the most options, from the S-3 Reference SACD player/USB DAC [HFN Aug ’24] and Z-3 network transport; through X-3 clock generator, D-3 DAC and P-3 preamplifier models; to stereo, mono and phono amplifiers. Meanwhile, both Series 1 and Series 2 keep it nice and simple: one integrated amplifier, a phono preamp and a standalone USB DAC.

Sanken style

The integrated Series 1 model – the £3300 A-1 – is rated at 2x80W/8ohm, while this step-up option claims a moderate increase to 100W/8ohm, doubling into 4ohm and reaching 400W/8ohm in BTL mode [see PM's Lab Report]. A solid-state amplifier, the A-2’s output stage uses four pairs of complementary Sanken transistors per channel, pair-matched during assembly, and a 600VA bifilar-wound toroidal PSU transformer. The fully balanced, symmetrical design adheres to Soulnote’s favoured ‘non-NFB’ topology, claiming the complete elimination of voltage feedback in the PSU, voltage gain stage and output stage. Of course, this does not preclude the use of current feedback… Soulnote also claims not to use DC servos or current mirrors in its ‘simple circuit layouts’, although it does employ (orange) LEDs in the biasing of its constant current sources.

Above: Seen with its upper PCB removed [carrying the switched attenuator network], the A-2’s main power amp, with four pairs of high current Sanken transistors per channel [far left and right], is revealed

There’s some hard-wiring of power and signal lines, plus a multi-layer PCB without, controversially, ‘even a single shield or filter that could negatively impact the sound’. Soulnote’s engineers, led by Hideki Kato [see boxout] have taken a similar less-is-more approach to the A-2 amplifier’s balanced resistor-ladder volume control, which uses relay-switching to set the output level across 36 steps, each marked by a very satisfying click.

Ribbed and ready

Considering this amplifier’s all-analogue nature, connectivity is rather generous. The provision of three sets of both balanced XLR and unbalanced RCA inputs means buyers could add the matching E-2 phono preamp [HFN Nov ’23] and D-2 DAC and still be ready for other sources. The A-2’s back panel is sensibly laid out, with inputs and speaker outputs clearly labelled for the amplifier’s different use cases.

Around the front, the A-2’s ribbed fascia is spoilt only by six minuscule LED indicator lights to denote the chosen source, a red numerical display showing volume setting, small rotaries for source and volume selection, a power button, and company logo. It all looks pleasingly minimalist and modern, and the feature-light nature of the A-2 pays dividends here – the complexity of its companion E-2 phono amp resulted in a fascia strewn with over 30 LEDs…

Spike it right

Similarly, only the mute, volume and source keys, plus the button that turns the display on and off, are enabled on the companion full-system RC1000 remote control. This handset requires line of sight with the sensor built into the A-2’s display, and the IR ‘window’ is a bit on the narrow side, which won’t favour those audiophiles who like to just wave their handset in the rough direction of their amplifier.

Also included are three metal spike pins, which can be swapped for the metal pole feet that come fitted as standard. Soulnote recommends doing this, and experimenting with the amp on different surfaces, to help tune the sound. The ability to manage vibrations entering the chassis, and any inherent microphony, has its merits, though how this idea marries-up with the A-2’s deliberately loose-fitting and inherently resonant perforated metal top plate is difficult to fathom.

Gentle giant
Perhaps I was pre-disposed to the A-2’s traditionalist vibe, but I wasn’t surprised to find its sound leaning toward refinement, light-touch musicality and a degree of warmth, as opposed to it being an amplifier eager to show off sheer, steely power and heft. In this way, it appears as deliberately engineered as Soulnote’s other components; an integrated amp for those seeking a little hi-fi luxury, not the up-and-at-’em excitement of some rivals.

Hooked up to dCS’s Vivaldi One Apex, an Aurender W20SE media server [HFN Mar ’23] and, at first, MoFi Electronics’ SourcePoint 888 speakers [HFN Jan’25], the A-2’s overall performance mostly put thoughts of super-charged competitors to the back of my mind. Okay, the rhythm section behind Tony Iommi’s crunchy power chords in Black Sabbath’s ‘Children Of The Sea’ [Heaven And Hell; Universal/Sanctuary 2735073] didn’t exactly shake the listening room, but as a whole the A-2’s delivery of this track was highly enjoyable, particularly the even handling of Geezer Butler’s tuneful bass lines, and its sweet, delicate delivery of the acoustic passages.

Above: Three balanced (XLR) and three single-ended (RCA) inputs serve the A-2 in stereo guise with the left inputs 1 and 4 used in bridged/BTL mono mode and in ‘power amp direct’ mode. Single sets of 4mm speaker terminals serve all modes

It was a similar experience with Madison Cunningham’s ‘Beauty Into Cliches’, from For The Sake Of The Rhyme [Verve Forecast; 96kHz/24-bit] – the drum kit sounded suitably attacking and the guitar riffs had a gritty edge, while the bass remained thoughtful rather than explosive.

Fiction romance

Yet that’s not to say the A-2 isn’t able to excavate lush lows when the music demands it. Alex Reece’s ‘Pulp Fiction’ track [Metalhedz METH011] came with a hearty dollop of opulent, round-edged bass, while the rapped lyrics on Massive Attack’s ‘Karmacoma’ [Protection, Wild Bunch Records; WBRCD2] sat atop deep, rolling LF effects, while eerie samples whirled around the soundstage. Indeed, the ability of Soulnote’s amplifier to paint this trip-hop piece with a big, focused image was a delight, and it repeated the trick with Elton John’s ‘Honky Cat’ [Honky Chateau; Mercury 528 162-2], sending the bluesy piano and banjo to either side of a wide stage, peppered by stabs of brass and flurries of sax.

This album opener is ol’ Reg and producer Gus Dudgeon at their most playful, and the A-2 fell into line, punching out its funky, stop-start rhythm with a fine sense of groove and drive. The whole shebang sounded effortlessly clean and crisp too, avoiding any top-end harshness.

Fast reactor

Sticking with hi-fi demo fodder, in the shape of Antonio Forcione and Sabina Sciubba’s Meet Me In London set [Naim Label; 192kHz/24-bit], the way the A-2 unpicked the lilting ‘Caruso’ was seriously impressive, easily conveying the distinct timbre of nylon guitar strings, and the female vocal, with its believable tone and smooth, articulate treble.

‘Aspan’, by the guitar-playing trio of Al Di Meola, John McLaughlin and Paco de Lucía [Passion, Grace And Fire; Sony Music International; DSD64], is another pristinely recorded acoustic jam, full of big echoey decays and the twang and snap of the lower strings, and this also seemed to fit the A-2’s sonic signature to a tee. There’s a lot of fast finger work and harmonics on show here, making it a great demo piece in terms of speed and attack, and, subjectively, Soulnote’s amp never missed a beat or note, leaving me to savour all the complexities of the group’s playing.

So, the A-2 can do sweet and light, clean and musical, and is fast on its feet. It also sounds a bit ‘polite’ at times, meaning it’s not an amplifier for all tastes, and isn’t preposterously powerful either – although what power it has still proved able to drive big speakers, as evidenced by swapping out the MoFi models and replacing them with PM’s reference B&W 801 D4 Signatures [HFN Sep ’23].

Above: Soulnote’s RC1000 ‘remote commander’ is used across its CD/SACD players and amps. For the A-2 only the input, volume, mute and display on/off functions are used

With that change made, ‘Anti-Hero’ [Midnights (3am Edition), Republic Records; 48kHz/24-bit] was an emotional, involving listen, its army of multitracked Taylor Swifts centred between the floorstanders, the vocals sounding gauzy and ethereal. But it was the ‘Gladiator Orchestra Suite: Part 1’, from The World Of Hans Zimmer – A Symphonic Celebration [Sony Classical 48kHz/24-bit], that really proved the A-2’s mettle. Presenting it as a big wall of effects, the amp sent me to a world of Middle Eastern choral singing, underwritten by one continuous Wagner-style low string note. As it built to its crescendo, the sound of the choir and players in the Wiener Konzerthaus felt massive. As Russell Crowe’s gladiator asks: ‘Are you not entertained?’

Hi-Fi News Verdict

Not for Soulnote a feature-laden, turbo-charged ‘super-amp’ offering the latest in network and digital connectivity... Instead its mid-level A-2 integrated is all about a focus on performance, and it succeeds with a detailed, delicate delivery that will suit your library of pristine recordings. Classical, jazz and acoustic pieces are its bread and butter, but the A-2 will endeavour to draw out the ‘lushness’ of every genre.

Sound Quality: 82%