Solid State Power Amp Reviews

The warm-up issue
For more than two weeks, I played and tinkered with the new M1X setup, trying to get the sound a newly redesigned $71,000/pair monoblock duo can reasonably be expected to deliver. At first I found it unnaturally warm, bass shy, and monotonic. Boring. Undeniably, the M1Xs exhibited exceptional natural flow and a smooth top, but nothing sounded quite as I thought it should.

I changed brands of speaker cable and interconnects, but inasmuch as I could hear changes, the sound remained dull. To make sure I hadn't inadvertently made some other important change in the system or the room, I switched back to my reference D'Agostino Progression M550s, making sure everything was tuned properly. The system returned to the sound I'm accustomed to. Each time, I followed my standard, energy-saving warm-up protocol of an hour or two before critical listening (footnote 5).

It was not until day 18 of the review period, when I conducted the Zoom interview with Haas and the men in Japan, that I learned the root cause of the problem. "The M1X requires a very long warm-up time," Machida explained. "I recommend at least 8 hours." I did my darndest to keep a straight face. "When we bring them to shows, the first day, they are not at their best. They sound better on the second day and best on the final day."

"Without music, it will take more than 48 hours to reach [peak] performance, I'm afraid," Machida said.

I invited Machida to speculate why warm-up was so long. "I guess the long warm-up is related to bias current and the size of the power supply, especially the transformer size. The S-05"—a smaller Esoteric amplifier that Machida says warms up quickly—"is a class-A design that always draws large current and gets really hot, while the M1X is a relatively a cool class-AB amplifier. Perhaps the long warm-up time is because the M1X always runs current relatively low, with a huge 3000VA power transformer that is nearly three times bigger than in similar amplifiers on the market."

Haas counseled me to leave the power-saving switch in the Off position to prevent the amp from going into standby mode after 30 minutes with no input; I already had it in that position. While 400W per channel was less than what some other amplifiers I've reviewed consumed, leaving the M1Xs on for hours was going to bias my next electric bill.

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Ready for prime time
To test whether warm-up really required more than 48 hours, I warmed up the Grandioso M1Xs for 15 ½ hours then ran music through them for another 2 before my friend Scott arrived for a second listen. On "Sweet Sue," from Four!, Hampton Hawes's 1958 album with Barney Kessel, Shelly Manne, and Red Mitchell (24/192 FLAC, Craft Recordings/Qobuz), bass was tighter, more colors emerged, and strings possessed more richness. But the sound was still unduly warm and homogenized, and dynamics and clarity were subpar. Grant Green's "Idle Moments," the title track from his classic 1965 album (24/192 FLAC, Blue Note/Qobuz); the first track on Caroline Shaw's Let the Soil Play Its Simple Part, with Sõ Percussion (24/96 MQA, Nonesuch/Tidal); and the beginning of François-Xavier Roth's period-instrument rendition of Mahler's Symphony No.4, with Les Siècles (24/96 FLAC, Harmonia Mundi/Qobuz), all sounded too warm, with undersaturated tone color. Scott left unconvinced that the Esoterics would ever shine.

No more chance-taking. After three days of playing music nonstop, getting uncomfortably close to deadline, I took a deep breath and settled in for a make-or-break listening session. Roon Radio settled on Grieg's Peer Gynt Suite No.2, performed by the WDR Sinfonieorchester Köln under the baton of Eivind Aadland (16/44.1 FLAC, Audite/Tidal).

The sound was natural, relaxed, alive, and convincing on both the Peer Gynt Suite and Let the Soil Play Its Simple Part. Percussion had gratifying presence on a wide soundstage and was correctly colored. "Very open, transparent, and clear," I scribbled. "I love the midrange. Colors are seductive. Just gorgeous." "Sweet Sue" sounded as Hawes might have hoped it would sound. The third movement of Mahler's Fourth symphony was open and flowing, mesmerizing in fact. Late pianist Lars Vogt's insight-rich final chamber recording, Schubert: Works for Piano Trio & Arpeggione Sonata, with the Tetzlaff siblings (24/96 WAV, Ondine), transported me to bliss. I also revisited a bluegrass track, "Lost Indian" from Norman Blake & Tony Rice 2 (16/44.1 FLAC, Rounder/Qobuz), and relished anew the distinctive timbral and expressive qualities of the two guitars, which blew me away when I first played this track with the D'Agostino Progression M550s.

As I worked to understand these amplifiers—to figure out how to get their best all the time—I found that keeping them on 24/7 and running music through them for two hours before listening produced optimal sound. Dynamics were not as jaw-dropping extreme as through the D'Agostino Progression M550s, but the sound was gorgeous. Musical flow on the Chiaroscuro Quartet's latest recording, Mozart, The Prussian Quartets (24/96 WAV, BIS), was lovely; it may be unusual to compare an amplifier to a DAC, but the Grandioso M1X's ease, flow, and detail reminded me of the sounds produced by the Vivaldi Apex DAC/Upsampler Plus/Master Clock. I didn't recall ever before hearing the resonance of Claire Thirion's gut-stringed cello, let alone being able to compare it to Tanya Tetzlaff's fuller, richer sound. The Grandioso M1X's ability to maintain tonal quality, fullness, and detail during soft passages was exceptional.

On the John Coltrane Quartet's "Nancy (with the Laughing Face)," from Ballads (24/96 FLAC, Impulse!/Qobuz), music and musicianship were sublime. With the M1Xs fully warmed up, Tidal's 24/96 MQA version had a more sonorous sax, better bass, and a more coherent sound than the Qobuz FLAC version. Bass was prodigiously powerful on Yello's "Electrified II," from Toy (24/48 MQA, Polydor/ Tidal), the music less brash and more inviting than through my reference system. Malia and Boris Blank's "Celestial Echo," from Convergence (16/44.1 FLAC, Boutique/Tidal), also surprised me with its thoroughly believable bass. On Yosi Horikawa's "Bubbles," from Wandering (16/44.1 FLAC, First Word Records/Qobuz), the sound of dropping balls was mesmerizing in its color and texture, and bass was stunning. The M1X's bass aptitude was demonstrated once more in Terje Isungset's "Fading Sun," from Winter Songs (Ice Music) (16/44.1 FLAC All Ice Records/Qobuz).

In contrast to the strong colors and forward upper range I customarily experience with the Progression M550s, the Grandioso M1Xs displayed a slightly buffed, dominant midrange. This complemented Fleetwood Mac's recording of "Black Magic Woman," from The Pious Bird of Good Omen (16/44.1 FLAC, Blue Horizon Records/ Tidal). Soprano Ruby Hughes, on Echo (download, 24/96 WAV, BIS), sounded heavenly. Seduced by her artistry, I turned to her contribution to United Strings of Europe's Renewal (16/44.1 FLAC, BIS/Qobuz) and discovered strings beautifully fleshed out behind her voice in a believable array. Every instrumental line was clearly delineated and imbued with natural color.

Considering how well the M1Xs performed with the Rossini Apex DAC/Vivaldi Master Clock combo I used for this audition, it would have been exciting to pair them with the even more revealing and flowing Vivaldi Apex DAC/Master Clock/Upsampler trio. Unfortunately, the Vivaldi was away on JA1's bench for measurement.

Conclusion
I've never auditioned a monoblock quite like the Esoteric Grandioso M1X. Its burnished sound flows effortlessly even through complex passages, and its somewhat laid-back presentation, from top to bottom, helps expose fine detail. The smooth, captivating midrange, which produces no listening fatigue, and impressive bass will speak to many an audiophile. Warm-up time and cost notwithstanding, the Esoteric Grandioso M1X is warmly recommended.

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Footnote 5: By review's end, I had switched back and forth between monoblocks three times.