Esoteric Grandioso M1X monoblock power amplifier

Of all the brand lines I've reviewed, none's sound has changed as much over time as Esoteric's top-tier Grandioso series. When I first encountered Grandioso setups at shows, they consistently sounded dark. That in itself is not necessarily bad; the darker presentations of some concert venues and hi-fi systems often enhance detail. But I prefer my music more illumined, with all the color and brilliance that instruments and voices can offer. And over the last three years or so, Esoteric's sound has become better lit, as though a 40W bulb was replaced by a 75W bulb.

At AXPONA 2022, I eagerly headed to the company's exhibit, where I spoke with Keith Haas, national sales manager of 11 Trading Company, Esoteric's US distributor. When I learned of the forthcoming Grandioso M1X monoblock ($35,500 each), the culmination of a complete revision of the company's top-selling M1 monoblock (now discontinued), I worked with Haas and Editor Jim Austin and set up a review.

As excited as I was, though, I grew concerned when I noticed that the M1X's specified compatible loudspeaker impedance is 4–16 ohms, and that specified maximum output power is rated only down to 4 ohms. Could the M1X handle my Alexia V's impedance dip, to approximately 2.5 ohms at 85Hz? (footnote 1) In a Zoom session with Haas; Esoteric's marketing and international-sales managers, Hiroyuki Machida and Tsuyoshi Sugiura; and the company's digital marketing, website design, and social media guru, Shota Terai, Terai told me that it could. "Our manual has to conform to Japanese safety standards," Terai explained. "This is why we limit our recommendation to 4–8 ohms. But the amplifier's performance [extends farther] than what's on the spec sheet; its linearity extends to 2.4kW into 1 ohm." (footnote 2)

Sizable simplicity
Machida explained that the head of research and development wanted the M1X to produce a more "natural and realistic sound" than the "audiophile sound" of the M1. "In his opinion, audiophile sound has some additions to it. The bass, for example, sounds extremely punchy because there's a boost around 112Hz to make it much as possible to achieve pure performance. It's 150% larger than the M1 but has fewer parts.

"Basically, the M1X is a very small-scale amplifier with a very big 19kg/3000VA power supply that [with its associated components] occupies 60% of the internal space," Machida said. "It's huge, and it can drive any speaker. Our engineer thinks its size is very important, especially for producing high power. Nonetheless, to open up the sound and preserve all the harmonics in the recording, he thinks the circuit should be very simple.

"You can't see it, but underneath the power supply board for the main drive stage, there is another, smaller transformer and board for the predrive stage. So there's a lot of power supply in one box. We use independent power supplies for the drive stage and predrive stage because if we don't, and we turn up the volume all the way, power supply fluctuation obscures clear presentation of instruments during climaxes. By separating the low-level voltage amplification stage, you get a clear presentation at top volume. You hear all the harmonic richness, even with a lower-efficiency speaker, and detail is maintained at all volume levels.

"Our amplifier uses a very simple, single-pole design for the phase corrector [phase compensation circuit]; other manufacturers use multiple poles. We also use parallel capacitors with a total 60,000µF in the drive stage. "The input stage is balanced, but all amplification after the voltage-amplification stage is single-ended. The original M1 design used 6 parallel push-pull transistor pairs; now we use 12 parallel push-pull pairs but with simpler circuitry, reduced parts [count], and better control of the drive stage. Complementary pairs of PNP and NPN transistors are arranged in a unique way on two parallel, vertically mounted modules. One module holds the PNP transistors, and the other holds the NPN. This keeps the temperature of the transistors uniform. If you situate PNP and NPN transistors together on one module, one above the other, the temperature of the lower row is significantly different from that of the upper row. Varying temperature leads to variations in the output current. This was a problem in the previous M1 design. [The result is] better-controlled sound. To ensure that the signal path between PNP and NPN pairs is no longer than it was previously, we use a [much] simplified circuit with extremely short signal paths. We also use a unique airflow technology to help maintain the temperature and create uniform performance."

With the aid of a slide presentation, Machida then clarified the purpose of the unique dual-honeycomb design of the grille in the amplifier's semifloated top. Esoteric claims it helps "maximize the efficiency of the internal heat exchange and to reduce the top panel weight as much as possible to enhance sound openness." By stacking two grilles of different thicknesses so that their hexagonal perforations are offset, vibrations are dispersed more efficiently.

Esoteric's website—one of the most elegant, visually compelling, well-organized websites I can recall visiting—informs the reader that the M1X includes "extra-thick, copper-clad printed circuit boards, huge bus bars in the drive stage, and ultra-heavy–gauge cables with secure, lossless bolt-on connector system." The company claims that because internal impedance is reduced, the M1X can grip large-diameter woofers with authority. It also claims that its IDM-01 (Integrated Discrete-Amplifier Module), which was originally developed for the C1X preamp, and FET switches used in the input selector further enhance microdetail in music.

The gracefully curved front panel is machined from a 35mm-thick aluminum block. When turned on, the Standby/ On button centered beneath the Esoteric logo illuminates in ethereal blue. The amplifier's 136.75lb (62kg) body rests on the company's proprietary "high-precision metal pinpoint feet," which are said to reduce mechanical stress and improve sound.

The Grandioso M1Xs arrived each on its own pallet, impressively packaged and securely wrapped in plastic. A forecast mix of rain and snow meant I had to get them unpacked and brought indoors pronto. Unfortunately, I was feeling sick. Fortunately, my neighbors, retired policeman Nate Holmes and his son Sam, noticed my predicament and came to the rescue. We set the two M1X units on my Grand Prix Audio Monza stands and, at Haas's request, I let them stand on their own custom feet; I didn't support them with the Wilson Pedestals I use with my reference amps.

The M1X offers a choice of three input types: RCA, XLR, and Esoteric's proprietary ESL-A (ES-Link Analog) (footnote 3). I set the rear-panel input selector to XLR, the only type compatible with my fully balanced D'Agostino Momentum HD preamplifier. After setting the Auto Power Save switch to off—you'll find out why shortly—I connected my speaker cables to the easily tightened, widely spaced terminals. Finally, I connected a 15A power cable to the IEC outlet, which is far enough from both inputs and outputs to make cable separation a snap.

I ignored the trigger ports, signal ground knob, and software update port, and left the knob that controls front-panel illumination level where it was. (I love that blue light.) I didn't use the supplied power-cord support bracket or felt scratch-protector pads (footnote 4).

The M1X isn't equipped with the customary rear-panel on/off switch. Once you plug it in, you need only depress the large, unobtrusive Standby/On button on the front panel and wait a few seconds for the amplifier to be ready for playback, if not necessarily at their best.

Footnote 1: In the review's measurements section, John Atkinson wrote, "The minimum [impedance] value was 2.45 ohms at 85Hz; Wilson says the minimum is 2.59 ohms, at 84Hz. ... The effective resistance, which is calculated from the combination of magnitude and phase angle, is >3 ohms above 225Hz but drops below 2 ohms between 50Hz and 90Hz. The minimum EPDR is 1.15 ohms at 66Hz. The Alexia V is not as current-hungry as the earlier versions, ... but the V still needs to be matched with amplifiers that won't be fazed by low impedances."

Footnote 2: In the US, the M1X comes equipped with a standard, 15A-max IEC connection. That would limit input power—hence steady-state output power—to about 1800W, although higher instantaneous values are certainly possible.—Jim Austin

Footnote 3: Esoteric describes ESL-A as "the ideal method for preamp to amplifier transmission where the signal level is extremely low. Compared to the conventional voltage transmission, it transmits approximately 100 times more current, making it less susceptible to noise and sending the full energy of the music to the amplifier. Also, in principle, it is not affected by the impedance of the interconnects running between the preamp and amplifier."

Footnote 4: Although both are nice features, especially the latter, in an era of thick, heavy, stiff power cords.—Jim Austin

Esoteric Company
1-47 Ochiai, Tama-shi
Tokyo 206-8530
(042) 356-9100

Dennis in NJ's picture

With all the technology and engineering devoted to the Grandioso M1X, it is a shame it takes days to warm-up and sound its best. I would have hoped there was a solution to overcome this, and bring warm-up/opening-up time into the realm of hours. Maybe something like the "high bias" option of some Parasound amps. Perhaps this is not possible; but having to wait days for the sound to open-up is a deal breaker for me. Plus in these "green" days, it is objectionable to have to leave a 400 watt draw on all the time for peak performance! Maybe some clever solution can be devised by Esoteric as an upgrade.

Gregory68's picture

I just can’t see myself being that eccentric to have a listening room with the music always playing just so it was at its best. Turning up the bias seems like the option or perhaps some heaters to bring the amp up to operating temperature. Otherwise I really enjoyed the read.

Gregory68's picture

I just can’t see myself being that eccentric to have a listening room with the music always playing just so it was at its best. Turning up the bias seems like the option or perhaps some heaters to bring the amp up to operating temperature. Otherwise I really enjoyed the read.

Siegfried's picture

[Post removed due to offense content unrelated to hi-fi.]

georgehifi's picture

Nobody, if you can spend that on them, the electricity to run them is nothing to that person.

Cheers George

Scott From PT's picture

What would it be like to imagine that all humans deserve kindness and decency, even public figures, or those who love in ways that we don't totally understand?

Thank you to everyone here who posts in kindness, and my sincere compassion for those who can't enjoy a simple equipment view without viewing it through their own personal pain and fear.

Jim Austin's picture

Jim Austin, Editor

georgehifi's picture

Good BJT (bi-polar) amps "can't beat them" (Gryphon, Agostino etc etc)
Looking at the measurements particularly output impedance of an ordinary .26ohm (30 damping factor), indicates to me it could use very little global or only local feedback.
And that it can almost keep doubling it's wattage down to 2ohms,("2.4kW into 1 ohm.")!!!! it's got bags of current, and to get these kinds of other measurements with such low global or just local feedback is quite an achievement.
Should be a stunner to listen to.

Cheers George

Amblygona's picture

You'll need to moderate that post.

Jason Victor Serinus's picture

The alert has been sounded. How do you spell "toast?"


ok's picture

..craves for a follow-up.

Jason Victor Serinus's picture


johnnythunder1's picture

at Stereophile. Besides your beautifully written and insightful reviews (and I always come away musically enlightened as well) I'm always impressed about how much work you have to put into the set up etc. and the A/B-ing with these mega components that always seem to be assigned to you. It's obviously a labor of love and we are supremely grateful for the mental- and physical - effort you put into these reviews.

Jason Victor Serinus's picture

Greatly appreciated.


AnalogueFan's picture

This is very scary. This would be the first natural sounding amp, because the other amps altered the linearity of the frequency response in the 112Hz zone.
Those others are us, who can only hear our music, analog or digital, through altered amplifiers.
The only truth would be in Japan with the discovery of Esoteric.
What a revelation!