Solid State Preamp Reviews

Putting Soulution's best to the test
Depending on how high on your rack you wish to place the 727, you may need assistance hoisting its 62lb into place. Although it comes with its own specially designed feet, I placed Wilson Audio Pedestals beneath it because (a) I use them under my reference preamp and other components, and (b) listening confirmed that they contributed a bit more air and depth to the sonic presentation. Depending on the sonic isolation and sound of your rack—few supports have no sound of their own—your results may differ.

During the review, I auditioned the 727 with both Accuphase A-300 and Dan D'Agostino M400 MxV monoblock amplifiers. Other components included an Innuos Statement Next-Gen music server with PhoenixNET switch, a dCS Vivaldi Apex DAC/Upsampler Plus/Master Clock, and Wilson Alexia V speakers with Wilson LōKē subwoofers. At various times, I switched back and forth between the Soulution 727 preamplifier and the twice-as-expensive D'Agostino Relentless preamplifier. All input and output connections were balanced. You've read it here before, and you'll surely read it here again: When reviewing any top-level preamplifier from a company known for superlative sound reproduction, the fundamental challenge is to get a handle on its sonic signature. After weeks and weeks of listening, I'm still at a loss to find an adjective far more telling than "fabulous."

Let's start with the Soulution 727's bass. During my chat with Hammer, I asked what music he used to evaluate his products. Imagine my delight and relief when, instead of citing "Hotel California," Diana Krall, Patricia Barber, Ella and Louis, or any of the other usual suspects, he offered eight choice tracks that I'd never encountered at a single show.

The first two, the Hadouk Trio's "Parasol Blanc 2" from their 2007 release, Baldamore: Live at Cabaret Sauvage (16/44.1 FLAC, Naïve Jazz/Qobuz), and the Renaud Garcia-Fons Trio's "Berimbass" from their 2005 album, Arcoluz (24/48 FLAC, Galileo Music Communication/Qobuz), demand a lot from a preamp. In both cases, the Soulution 727 responded with bass that was absolutely firm, precisely pitched, and correctly colored. No matter how fast the astounding bassist Garcia-Fons moved between pitches octaves apart, the 727 was right there with him, sounding completely undaunted and at ease. How the man changes colors and textures—his fundamental sound—as he moves between Western and Eastern idioms, I do not know; all I know for certain is that the Soulution 727 conveyed his every shift, leaving me in awe of his (and its) virtuosity.

Bass is hardly these tracks' only raison d'être. "Parasol Blanc 2," for example, abounds in color contrasts created by instruments pitched many octaves apart. No matter how distinct the contrast, everything came through with ease, and far cleaner than through my desktop system's DSP-abetted subwoofer.

I didn't begin my audition with jazz tracks, however. Instead, I chose a recording I immediately decided to review: Kristian Bezuidenhout's performance, on a historically authentic fortepiano from 1805, of Mozart's Piano Concertos Nos.19 & 23 (24/96 WAV download, Harmonia Mundi), accompanied by the period instruments of the Freiburger Barockorchester. Through the Accuphase A-300s and the Soulution 727, the midrange sounded gorgeous and the highs alive but not too bright. The unique sound world of period instruments came through gloriously. I especially savored how the fortepiano sounded distinctly more percussive than a modern Steinway, with a more pointed, less sustained sound that showcased its harpsichord-like sparkle.

Beyond that lay the feelings inspired by the notes. I cannot begin to convey how delightful the opening movement sounded—how happy it made me feel—and how well the Soulution 727 transmitted the unique tang, more distinct leading edge, peacock-worthy color display of period instruments. I was in heaven, and I also marveled at how perfectly the orchestra followed Bezuidenhout's lead, and how well the preamp enabled me to hear the orchestra's ability to mirror its leader's phrasing. By recording's end, I knew that the Soulution 727's truth-telling veracity—its truth to the source—was something to cheer about.

The grounding upgrade
Barely a week into the review, and just four days before I left to cover the Warsaw Audio Show, I heeded the urgings of Audio-Ultra's Edward DeVito (footnote 7) and upgraded my grounding system. Admittedly, I had my doubts that anything much would come of the upgrade. After all, I'd had my electrical ground professionally measured, and it had been declared adequate to the task of high-end audio. Still, because Ed had proven correct and delivered in every electrical upgrade he'd suggested and carefully supervised, I decided to give it a try.

My original grounding system consisted of a very short run of 8-gauge copper wire to an 8' copper ground rod buried in mostly dry ground on the side of our house that is shielded by a roof overhang and our side entrance steps. While the national electrical standard stipulates an impedance of 25 ohms, copper's natural corrosion over time had raised my impedance to between 120 and 130 ohms. As I now know, the impact on sound was major.

Ed, carefully guiding two installers from Frederickson Electric, ensured that we would not intersect pipes and power lines as we upgraded every aspect of my grounding system, including the nature and location of rods. If I remain intentionally vague on the process, it's because I don't want to be responsible for someone setting fire to their home or disrupting power to their neighborhood because they decided to proceed on their own. What I will share is Ed's dictum: "I recommend testing the impedance every 4 to 5 years. Don't let it get higher than 25 ohms before beginning the process over."

I barely had time to listen before I was packed and on my way to Europe. But listen I did. I couldn't believe how much more silent and coherent the presentation had become. It was as though every issue I'd ever had with my system, save for room dimension–related brightness, had magically resolved.

Many people had told me previously that grounding was one of those final frontier journeys essential to getting the most from a sound system. Given how good my grounding already was, I thought I'd already done what needed to be done. How wrong I was, and how delighted I am by what I now hear. Better equipped than ever to evaluate subtle differences between premium components, I returned to listening.

The sound got even better
Wishing to dwell longer in period instrument paradise, I turned to Ernst Schlader's marvelous performance, on a superbly voiced copy of an historically appropriate basset clarinet, of Mozart's Clarinet Concerto. Schlader's virtuosity, on the Pentatone recording of Mozart: Symphonies 29 & 33 • Clarinet Concerto (24/96 FLAC download, Qobuz), is enhanced by the colorful period instruments of Akademie für Alte Musik Berlin, led by concertmaster Bernhard Forck.

What I loved most was the unforced, natural, unadorned sound of every instrument. "It sounds beautiful as hell," I wrote in my notes. "Forget about playing the first three minutes; I'm listening to the whole damn thing, deadline be damned. I can't believe I'm being paid to do this."

With my new, superior grounding setup, I heard even more of the basset clarinet's distinct natural tang than when I reviewed the album some months before. This was not the first time when self said to self, if I had to choose between listening to this performance in a seat halfway back in a concert hall or on my system, I'd choose my system. Of course, the price of admission is ultimately far higher.

At that point, I called a halt to my mental chatter and proceeded to audition all the other recordings on Hammer's list. On the Helge Lien Trio's "Gamut Warning" from Hello Troll (24/96 FLAC, Ozell/Qobuz), cymbals were perfection itself. True to expectations, bass was totally in control and impressively deep. But there was something more. It's rare that any system has enabled me to feel the visceral impact of plucked strings as they vibrate against the neck of the double bass, but the Soulution 727, with more than a little help from the trio's sound engineer, made that possible. Score one in the gobsmacked department.

It had been a while since I'd heard the voice of Melody Gardot. On "March for Mingus," from her 2018 album Live in Europe (24/48 FLAC, Decca/Qobuz), I quickly learned that she, like Patricia Barber, chooses her backup musicians so carefully that they can easily enthrall on their own. As expected, the sound again remained clear and uncongested when everyone got going at once.

Comparison
I can't be the only Stereophile reader who is so eager to detect differences great and small between the performance of two very differently priced premium preamps, the Soulution 727 and the twice-as-expensive three-piece Dan D'Agostino Relentless, that, in my case, I switched back and forth three or four times. To anyone, including my editors, who says it's unfair to compare a one-piece $75,000 preamp to a heavier three-piece $150,000 preamp, I say, "As much as I hear you, I also know that many people who can spend $75,000 on a preamp can also shell out twice as much for one if they feel so inclined." So, at the risk of facing a firing squad, here I go.

The first thing to note is that these preamps exemplify polar opposite design aesthetics. That alone, rather than price or sound, will prove the decisive factor for many individuals. As much as sundry pundits and, Lord help us, TikTok influencers may proclaim that audiophiles only give a rat's ass about aesthetics when the preferences of their significant others come into play, I've seen far too many photos of beautifully designed listening rooms to believe that malarkey. In the audiophile fiefdom, going with the flow refers to more than sound.

Beauty resting in the eyes of the beholder, it seems best to steer clear of that hornet's nest and move on to sound. In my system and room, the Relentless threw a wider and deeper soundstage. It also surrounded instruments and voices with a lovely extra cushion of air, yet sounded even faster than the impressively fast 727. While this airy, plush cushion smoothed out harshness and warmed the sound a bit, it also paradoxically smoothed out timbral distinctness. Ultimately, on period instrument recordings, I felt the Soulution 727 better emphasized period instrument tanginess, but the Relentless rendered their attacks with more snap. That may sound contradictory, but it's what I heard and confirmed during multiple listening sessions.

Ultimately, comparing these two state-of-the-art preamps was anything but a simple case of black and white. Which preamp I preferred depended as much on which set of monoblocks I paired it with as what recordings I played through it. To those who can afford either preamp (or both), the only sensible path forward is to listen to them on your own system with the music you love. The sound of your associated components (including cables), power treatment, and room acoustics will ultimately prove central to which you choose.

What I know beyond question
The Soulution 727 preamplifier is one of the finest-sounding components I've heard in my system. Its bottom line is unadorned honesty. Timbres are absolutely, incontrovertibly, certifiably 100% natural, uncolored, and true-to-the-source. In addition, control is impeccable from the deepest bass to the most stratospheric highs, and timing is excellent.

If I weren't a reviewer whose responsibilities require that I parse for fine differences, I wouldn't have thought an iota about all that PRaT stuff (footnote 8). Instead, I would have felt as I did the first time I heard the Soulution 727 in my system: This preamp really has no sound of its own. Rather than impose a distinct sonic signature, it gets out of the way of artists and engineers and lets music and the emotional truth it conveys speak for itself. The Soulution 727 deserves Stereophile's highest possible recommendation.

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Footnote 7: See audio-ultra.com/a-c-power.

Footnote 8: PRaT = pace, rhythm, and timing.