Some integrated amplifiers seem to know better than others how to make the speakers they’re driving sound best.
And then there are some integrated amplifiers, only a handful in my experience so far, that seem to know much better than that. It seems, or sounds, to be nearly the case that this rare breed of integrated amplifiers had a hand in designing whatever speakers you send their way. A kind of intimate understanding and the Soulution 331is one such beautiful beast.
This level of performance also means that anything goes when it comes to music choice and no matter what you pick to play, it’s also going to sound its best assuming you like what your speakers do. Wins all around and the only potential drawback to an amp like the Soulution 331 is the price of admission which is a personal matter as discretionary spending on things like hifi have no moral or ethical bounds so long as you live in the real world. A bitter pill to swallow for those people who believe the appropriate amount of money to spend on a hifi is about what they’ve spent on theirs, the kind of rationalizing that only makes sense in a mirror—one peak out a window and that illusion is shattered.
The Soulution 331 is an updated version of the Soulution 330 integrated amp I reviewed in November of 2023 (review), about which I concluded (in part):
…the Soulution 330 integrated amp is among the finest amplification devices I’ve had the pleasure to live with. It is a clear stand out performer in every meaningful way, enriching all of the music I asked it to play.
Soulution summarizes the main difference the 331 brings as follows: “More power reserves and less phase shift in the audioband make the 331 sound even more lifelike than its predecessor”.
Here’s a bit more detail from the company:
Four new cutting-edge switched-mode power supplies modules deliver 1,200 VA of continuous power for the power amplifier section with a peak power capability of up to 4’200 VA for more than 5 seconds. They feature high performance filtering at the input and output, and high speed Soulution voltage regulators to deliver considerably more stable power than any conventional, transformer-based technology.
Like the 330, you can think of the 331 as a separate preamplifier and power amplifier in one chassis. The 331’s three stage current amplification is based on technology used in the company’s Series 5 amplifiers and runs in “high Class A operation supplemented by more than 160,000 µF of storage capacitance”. Output power is rated at 100 Watts into 8 Ohms, doubling into 4 Ohms and again into 2. It’s worth noting that the 330’s output was rated at 120 Watts into 8 Ohms and I’m all for less (power) when it’s more (quality).
The mechanics of the 331’s volume control takes some explaining and I’ll let Soulution do the heavy lifting:
Relay-switched high precision metal foil resistors form an 80 step (1 dB) volume control. To avoid unpleasant clicking noises or harmful voltage peaks during volume adjustments, the 331 is provided with a second volume control path which is active only during volume adjustments. This secondary, IC based volume control alters the volume without any click or pops. Once the new volume is set, the 331 will revert to the sonically superior path with its high-precision metal foil resistors. The frequency bandwidth of the preamplifier section could be extended to more than 2MHz (-3dB), which does significantly reduce the phase shift in the audio band.
The review unit came with the optional DAC and MC Phono modules which also have their own dedicated circuits and join the 331’s standard 4 analog inputs (2x RCA, 2x XLR), 1 pair of balanced XLR out, and a set of speaker binding posts. The DAC, which is built around the Burr Brown/TI PCM1792, offers 4 digital inputs including Coax SPDIF, AES/EBU, Ethernet/Network, and USB. I used the AES input fed from the Barn resident Grimm MU1 (review) using a length of AudioQuest Diamond AES cable mainly because the 331’s network input does not support Roon and Roon has become an essential part of my music enjoyment. Essential. And I will note that the Grimm MU1 is one of those network players (+Roon server) that seems to know everything there is to know about getting the best from any DAC it’s connected to.
In terms of fit ‘n finish, I appreciate the 331’s simple minimal design with subtle flourishes like the gentle U-shaped brushed aluminum curved chassis and 3/4 length black heatsinks on either side. The minimal front panel has a red LED display, 3 buttons for power, mute, and program, and a multi-function rotary knob that controls volume, volume-DIM, and input selection while also stepping through the numerous options when in Configuration Mode that include Min and Max Volume settings, Balance, Multi-Amp Mode, Phase, Phono stage High Pass Filter (on/off), DAC filter options, and more. I recommend a read through the 331 manual for the complete story. Build quality is above reproach and the included remote is an interesting, if unusual, shape that fits into the hand nicely.
Three pair of speakers had the good fortune of playing with the Soulution 331 including the recently reviewed Canton Reference 2 (review), Gauder Akustik Capello 100 (review), and the Barn resident DeVore Fidelity O/96 (review). In addition to using the 331’s internal DAC, I also let the Grimm MU1 (review) feed the Barn resident totaldac d1-unity (review) while analog duties were handled by the Barn resident Michell Gyro SE/Sorane SA1.2/EMT HSD 006 rig (see full system and Barn details). The 331 arrived in late November so I had just over 2 months of listening time all told.
Regardless of the speakers in play, the Soulution 331 offered stunning transparency, effortless control including Earth-shaking bass, the kind of dynamic performance that made me say “wow” out loud along with other less PG exclamations, a sound image as solid as real life filled with the sounds of music that were as finely nuanced, detailed, and naturally voiced as I’ve had the pleasure to live with. One real standout aspect among the 331’s many standout qualities is its ability to sculpt finely delineated musical details down to microscopic levels while allowing them to unfold within a believable three dimensional space. The things that make music not only rang out true but they resounded in space as solid dimensional sources of sounds filling space in every direction with an uncannily lifelike sense of attack and decay. While it’s been more than a year since the Soulution 330 left the Barn, my sense of excitement and wonder having spent the past 2 months or so with the 331 leads me to believe Soulution has delivered on its upgrade promise.
The only amplifiers I’ve heard do this 3D thing as convincingly, and a touch more-so, are the Riviera Labs Levante (review) and Riviera Labs APL10 Preamplifier/AFM25 Monoblock combo (review). Translated into real world experience, there were a number of times during the Soulution review period when I mistook sounds coming from the speakers with sounds coming from real things happening in or around the Barn. One particularly gnarly deep passage from Mabe Fratti’s stunner from 2024 Sentir Que No Sabes had me get up to see if a delivery truck was headed up the driveway. No joke.
I’ve written about Mabe Fratti’s music many times before so you may remember she is a Guatemalan cellist, composer, and vocalist and Sentir Que No Sabes is among my favorites of her records for its lean into song structures while keeping her adventurous spirit in sounds, forms, and textures. This also makes Sentir Que No Sabes a great record for sussing out a hifi’s ability to deliver various acoustic voices, electronics, vocals, and sounds as thick and rich as a tropical rain forest and the Soulution 331 driving the DeVore O/96 nearly made it rain inside the Barn. The 331’s ability to provide shape and substance to even the smallest of sounds adds to the scale of a musical event which brings with it real drama, making music that much more involving, that much more exciting, and when quiet passages drift through real wonder at the sheer quality of the sounds of cello bowed, plucked, and strummed with countless tones and overtones bouncing around the Barn. A fireworks display in sound. Lovely.
Raw sexy power. PJ Harvey’s compilation The Peel Sessions 1991–2004, released in 2006, is all raw, sexy power and opener “Oh My Lover” is a tutorial on how to get everything you need and then some from a three-piece band and the rest of the tracks that were to appear on Harvey’s debut Dry drip with the same ferocious energy. You might think that this kind of music doesn’t really need a fancy hifi and in some ways that’s absolutely true and I submit a few decades of listing to and loving PJ Harvey’s music through all manner of music reproducers, from a phone to a car to a club to live to whatever hifi I had at the time. That said, the thing a great hifi brings to the table is more and if we’re doing nothing but listening, more is always better. More is more.
Here’s a thought on the old hifi chestnut that goes a little something like this—we need to listen to live acoustic music on a regular basis in order to judge how good, or bad, a hifi is. As if everyday sounds like voices, birds, the wind, cars passing by, sirens wailing, thunder, waves crashing, and so on have no value when it comes to hifi and just typing these thoughts make that old chestnut seem kinda silly, no? For me that’s a hard “yes” as the real issue isn’t so much about what we’re listening to as much as it is about just paying attention.
With the Soulution 331 driving (the daylights) out of the recently reviewed Canton Reference 2s, to live-like levels I was overwhelmed by PJ Harvey, Steve Vaughan, and Rob Ellis as if there was nothing between me and them but space. Even time was erased which is one of the perks of paying attention to only the music.
I sung the praises of Tamsin Elliott & Tarek Elazhary’s 2023 debut release So Far We Have Come in last week’s review of the Pathos InPol Heritage MKII (review) and I’m going to keep singing here (and elsewhere) as its degree of sheer loveliness is nearly overwhelming created from a gaggle of instruments which include lever harp, piano accordion, quartertone accordion, flute, synths, Oud, guitar, fiddle, clarinet, bass clarinet, viola, and percussion with field recordings added for good measure. A cornucopia of sounds that the recently reviewed Gauder Akustik Capello 100 seemed to love as much as me. The Soulution/Gauder/Grimm/totaldac system made this worldly music come alive to a shocking degree with sounds sounding more real than representation from bottom to tippy top.
When reproduction reaches this level of quality—seamless, pure, and natural—my degree of enjoyment and involvement reach their upper limits, quieting my mind down to the point where there’s nothing but the music and its near infinite sonic qualities. In terms of comparisons, the Soulution amp is even more refined and nearly super-natural as compared to the Pathos which is pretty damn magical in its own right. The 331 also outdoes the InPol amp when it comes to that 3D recreation I mentioned early on that makes reproduced music feel fully formed in air to a greater degree which for me translates into that much more involvement and excitement. In the Pathos’ plus column is its ability to make music feel a bit richer and fuller, more timbral saturation, a quality that some listeners value most.
Another interesting foil is the Vinnie Rossi BRAMA Integrated Amplifier (review) that offers a more fluid, smooth presentation and an even higher level of build quality while the Soulution strikes me as being even more resolving with a greater sense of unadorned purity. To my way of thinking, and you probably saw this coming, I’m not declaring winners and losers as the BRAMA and 331 are both super-refined and accomplished integrated amplifiers and the choice between the two will come down to subtle differences in presentation, features, looks, and company.
While we’re here, I’ll talk about the optional DAC and to cut to the chase—in my experience you won’t find a better sounding DAC for its price. But if you want to squeeze even more goodness out of the 331’s integrated amp, spending more, a lot more, will give you a meaningful return on your investment especially if you listen to music while doing nothing else for long periods of time. The Barn’s Grimm/totaldac digital front end costs roughly $25k and it’s much better than the optional $4275 internal Soulution DAC. Shocker! What this more gets you is greater delicacy, greater resolution, and even more of that 3 dimensional quality all adding up to a greater level of musical involvement but all that being said, the Soulutions DACs way with So Far We Have Come was still entirely engaging.
I also stepped through the Soulution DACs different filter options (Linear phase, Minimal phase, Linear phase with apodizing (default), and Minimal phase with apodizing) accessed through the menu system and I found the default Linear phase with apodizing to be my favorite. Your taste in filters may vary but this is a nice option that allows for subtle yet potentially important tweak-to-taste flexibility.
How about vinyl? I am much more inclined to spring for an optional MC phono stage in an integrated amp than a DAC as I’ve yet to hear an internal DAC equal a great DAC. The optional phono stage in the 331 did a lovely job with the bevy of records I asked it to play including one of John Coltrane’s masterpieces, Giant Steps recorded in 1959 and released in 1960. I recently picked up the Rhino stereo version, I sold nearly all of my records years ago (for the 3rd time in my lifetime) so I’m re-buying favorites and Giant Steps is a top 10 contender and it sounded rich, right, and rewarding in Barn through the Soulution/DeVore combo. I’ve mentioned this before but it’s worth repeating here—the EMT HSD 006 excels at pure energy and this highly valued quality came through the Soulution’s phono stage loud and clear which falls into the great news category in my book.
For my tastes and wallet, the less expensive Barn resident Aurorasound VIDA MK.II Phono Stage offers equal if not slightly greater resolution as well as greater flexibility when it comes to cartridge loading options—the Soulution offers variable impedance settings as well as a high-pass filter (on/off) accessed through the menu system. The Aurorasound also has 2 phono inputs which may appeal to multi-arm or multi-turntable owners.
Also according to my tastes, “Naima” from Giant Steps is among the most beautiful pieces of music ever made and the Soulution acting as phono stage and integrated amp let that beauty shine through in living color so if you own a turntable and Moving Coil cartridge(s) that you love, the Soulution’s phono stage may be all you need if you value a one and done phono/amplification solution.
No review is complete without some large scale classical which is where Einstürzende Neubauten’s 4th studio album Zeichnungen des Patienten O. T. comes in. Released in 1983, Drawings of Patient O. T. as it was released in the US was my introduction to the band so it remains a favorite for its dark, menacing über energy. In addition to their typical clatter and screech, found sounds and pre-digital sampling weave their way into the mix expanding the array of Neubauten’s noise-sounds to new levels. I am also a fan of Art brut, to borrow Dubuffet’s term, so the title’s reference to the drawings of artist Oswald Tschirtner is icing on this tasty industrial cake. With the 331 driving the Gauders into 90dB territory, the physicality of Neubauten’s music came across loud and clear with every bit of complexity in sounds, tones, overtones, harmonics, clatter and doom feeling perfectly sculpted in air with real life mass and energy. Stunning. This is the kind of music that is meant to overwhelm–not with sheer (Art) brut force as you might imagine, but with its love of noises in their infinite variety in the service of music which demand care and attention to sound quality and the 331 very nearly felt like part of the band. Nice.
During its 2 month+ Barn stay, the Soulution 331 proved to embody a kind of intimate understanding of the three different loudspeakers it was asked to drive but perhaps of even greater importance an intimate understanding of all of the music I asked it to play. The level of refinement, drive, voice, and physicality on display made for entirely captivating and deeply involving music-driven experiences that makes the end of this review period the only let down. The Soulution 331 is a standout product in every meaningful way.
Soulution 331 Integrated Amplifier
Price: $32,975 | optional DAC +$7225| optional MC Phono Stage +$4275
Company Website: Soulution Audio
US Distributor: AXISS Audio
Specifications
Mains: 100 – 240 V (50 – 60 Hz)
Power consumption: < 0.5 W Standby, idle 110W
Analog inputs: 2 × balanced (XLR), 2 × unbalanced (RCA)
Input impedance: 5.8 kΩ balanced (XLR), 4.9 kΩ unbalanced (RCA)
Phono input (optional): 1 × unbalanced (RCA)
Termination impedance: 20-1260 Ω
Digital inputs (optional): 1 × AES/EBU, 1 × SPDIF, 1 × USB, 1 × Network
LINK (remote turn-on): 2 x phone jack (3.5mm)
Pre-Out: 1 x balanced (XLR)
Loudspeaker: 2 pair loudspeaker binding posts
Power output:
120 W @ 8 Ω
240 W @ 4 Ω
480 W @ 2 Ω (< 5 sec.)
Output current max: 30 A
Gain line inputs: – 53 to + 26 dB
Gain phono input: +17 to + 96 dB
Frequency response (– 3 dB): 0 – 800 kHz
Phase shift @ 20kHz: < -3°
THD: < 0.0005%
Spot noise (input related): < -140 dBV/√Hz
Damping factor: > 5,000
Dimensions (WxDxH): 430 x 490 x 142 mm
Weight: ~18 kg
