Simaudio Moon Rock monoblock power amplifier

For years, I thought of Simaudio gear as good-sounding, attractive, and modestly priced, often describing it to friends as "really good for the money." The $5500 Moon Eclipse CD player, which I reviewed in our April 2001 and April 2003 issues, stretched the "modestly priced" descriptor a bit, but its sound was still, I thought, really good for what it cost, and I adopted it as a reference. Simaudio expanded the Moon series and eventually discontinued its older, less expensive Celeste brand, but, I thought, its products could still be described as "really good for the money."

Lots of mass, lots of power, lots of money . . .
During the mid-1990s, Simaudio's Pacific Rim dealers began to beg for a massive, hugely powerful amp to tap the exploding market in that region, so the Simaudio engineers came up with the Moon Rock monoblock. At 220 lbs, 1000W, and $18,500 each, the Rock is a dramatic departure from "really good for the money." Simaudio's vice-president of marketing, Lionel Goodfield, admitted that they "had been considering a completely insane preamp to go with it, but we've shelved that to focus on developing the new line." The new Moon Evolution series, which consists of the approximately $10k/each Andromeda CD player, P-8 preamplifier, and W-8 power amp, was shown at the 2005 Consumer Electronics Show and is slated for rollout this summer.

. . . and lots of technology
The Moon Rock distinctly differs not only from other Simaudio amps, but from its competitors as well. Just as the rest of the world is adopting a tall, svelte, narrow look for big amps, the Rock emerges as a massive near-cube. While other manufacturers perch their amps on spikes, the Rock is embedded in a solid slab of granite resting on elastomer feet. The standard way to generate lots of power is to combine higher-voltage power supplies with greater numbers of paralleled output devices. The Rock's architecture, in contrast, comprises two 250W amps, pseudo-bridged, one forming each phase of the differential topography. Lionel Goodfield admitted to me that this approach carries some baggage, but "It's simple. Lower-voltage amplifiers allow you to use more linear devices and tighter-tolerance parts."

Each Moon Rock is essentially four amplifiers in one. Signals are fed to an input buffer consisting of two Burr-Brown op-amps, which are outside the global-feedback loop. Next is the differential amp itself, which uses two matched J-FETs, followed by the voltage gain, pre-driver, and driver stages. Next is the output stage, and it, too, is unusual. It consists of nine pairs of Motorola MJL21193/94 bipolar devices, each decoupled by a 1500µF capacitor. The result, according to Simaudio, is an amp that's both faster and capable of generating much more current than is typical. The Rock's spec sheet cites big numbers: 95 amps peak, 45 amps continuous, and a slew rate of 120V/µs.

Other details: The expensive Moon Rock is entirely hand-built, critical resistors are matched to within 0.01% and others to within 0.1%, and the power supply, output, and ground wiring isn't wire at all, but 1/8"-diameter rods of high-purity copper. The power supply starts with a huge 1.1kVA transformer but then, extensively and separately, filters and regulates the power to 46 specific points in the circuit.

Is it all worth it?
I used the Simaudio Moon Rocks with a wide range of other gear, but my Thiel CS6 loudspeakers were constants throughout. The CS6's impedance is low, between 2 and 4 ohms across the audioband, so it takes a stout, well-designed amplifier to successfully control and drive it. Based on their prodigious specs, I expected the Moon Rocks to work well, and they did. There was absolutely no evidence of strain, regardless of what I threw at them—the sound had a relaxed, effortless feel.

This relaxed, flowing quality was deceptive—like a quiet, stable car that's a lot faster than it feels—and it led me to occasionally underestimate the Rock. For example, it sounded almost lazy, but actually wasn't slow or soft at all. With dynamic program material, the music was vivid and explosive. With soft, intricate interwoven lines, I was touched by the delicacy and sweetness of the music's detail. Sharp transients were exactly as sharp as they should be, no more, no less. In every case, the Rocks just seemed to sit there, impervious to whatever was happening in the performance.

To test their power and control, I cued up André Previn and the London Symphony Orchestra's performance of Messiaen's Turangalîla Symphony (LP, EMI SLS 5117), a challenging, often discordant work with wave after wave of complex, percussive passages. Different instruments, including a gamelan-like mix of percussion and a bizarre early (1928) electronic keyboard instrument, the Ondes martenot, enter and exit at various times, locations, and levels. When a system accurately reproduces the various instruments' complex textures and dynamics, these passages explode and tumble like spectacular, well-coordinated fireworks. Any incoherencies in how a system reproduces dynamic transients, however, will stand out crudely, blurring some of the firework streaks, or making them seem slower and disconnected from the others—or the initial transients may seem sharp while the notes are threadbare outlines that never solidify or bloom. The Rocks held everything together beautifully; when I closed my eyes, I could visualize sharp, clear cascades of Technicolor streaks painted across a three-dimensional panorama.

The Rocks also demonstrated their precision and control in how they reproduced Beverly Sills' vocals in La Traviata (LP, Angel SCLX-3780). In this performance Sills spans wide ranges of pitch and volume, often combining both in breathtaking transitions. The Rocks reproduced these transitions precisely, conveying their power without ever blurring the texture of her voice or the surrounding ambience—even as the volume grew and energized the hall more and more.

As impressive as Sills' transitions were, I was even more impressed that, in these dramatic passages, I could clearly hear her superimposing on the notes small variations in pitch and volume. This ability to resolve and portray inner detail, regardless of what was happening elsewhere in the performance, is something I've heard only with the Moon Rocks and with Classé Audio's Omega monoblocks—both of them hugely powerful super-amp designs.

Details like Sills' vocal nuances are often very subtle, but they significantly enhance the realism of even something as simple as a solo piano. I spent an evening listening to Vladimir Ashkenazy's reading of Beethoven's five piano concertos, accompanied by Georg Solti and the Chicago Symphony (LPs, London/Decca R215010). Every aspect of the piano's character, from the impact and pacing of the hammers hitting the strings to the reverberation of the soundboard, was faithfully reproduced. Gradations in dynamic shadings were as apparent at the frequency extremes as they were through the midrange, and Ashkenazy's subtle nuances of fingering and rhythm were resolved within both the softest and the loudest passages.

Lionel Goodfield told me that decoupling the output transistors gave the Rock an "aura of class-A operation"—even though the amp actually switches to class-AB above 25W—"but mated with nearly unlimited power and extended to the frequency extremes." And that's exactly how it sounded—like a really good pure class-A amp.

Genuine class-A amps, such as the Mark Levinson No.20.6s I use as references, are known for their gorgeous midranges. The Moon Rock's midrange was luscious, and the solo oboe lines in Rafael Kubelik and the Chicago Symphony's reading of Dvorák's Symphony 9, "From the New World" (LP, Mercury Living Presence SRW 18021), were great examples. They were quiet and well back in the soundstage, but still immediate and quite lifelike—and absolutely beautiful. I could detect the burst of air that preceded and initiated each note, then follow the rapid swelling of the warm, woody glow as the instrument began to resonate.

The Rock's performance at the frequency extremes was also excellent, but this was another area where its purity and ease were deceptive. My first impression was that its sound was "all midrange," soft and rolled-off on both ends. But when I listened closely, or made direct comparisons to the Levinson No.20.6 or my VTL Ichibans, it was obvious that wasn't the case. My initial impression just reflected the fact that the Rock's "class-A aura," as Goodfield put it, spanned the entire frequency range.

The Rock's bottom end was extended, tight, and powerful. It was also the most articulate I've heard to date, and made startlingly obvious the differences among timpani, bass drum, double bass, and cello. Leopold Stokowski and the Czech Philharmonic Orchestra's recording of Stokowski's Bach Transcriptions (LP, London/Super Analog KIJC-9118) was a great example. The differences between the bass drum's big, echoing boom and the timpani's rounded, more complex, organic sound were like night and day—even the first split-second of their initial impacts had distinctly different characters. And I've not heard any combination of amp and speaker illuminate individual double basses as well as the Simaudio-Thiel setup did on the Bach Transcriptions, or as dramatically showcase the different pacing and texturing of the players' bowing techniques.

The Moon Rock's high-frequency performance, too, was excellent, but often hard to get a fix on because of the amp's smoothness and low level of distortion. Listening to the upper registers of Ashkenazy's piano in the Beethoven concertos, I went back and forth—first thinking that the Rocks were a bit too soft, then deciding instead that they were dead on, and that any additional emphasis on a note's attack would make them sound a touch too hard.

Another indication of the Moon Rocks' superb high-frequency extension was the holographic nature of their image portrayal, which requires very accurate tracking of notes' super-fast leading edges. The best example of this was a performance of Delibes' Lakmé by the Orchestra and Chorus of the Op≠ra-Comique, Paris (LP, Seraphim SIC-6082). It's lovely throughout, and one of the most natural-sounding recordings I own, with wonderfully dimensional images on any good system. But when, through the Moon Rocks, I heard tenor Charles Burles (as Gerard) left alone on stage midway through Act I, I was dumbstruck. I hate to commit the sin of reviewer hyperbole, but hearing this passage through the Rocks made me feel foolish about ever having used the word holographic in past reviews.

I was impressed by the Moon Rocks. Their performance was outstanding in most respects, and even where I had doubts, they were usually addressed with a bit more listening. In a few cases, however, I noticed things about the Rocks' presentation that I couldn't quite reconcile. The first two, which I often hear from class-A amps, were a slightly warm tonal balance and a faint liquid texture. John Atkinson's measurements should shed light on the tonal-balance question; I couldn't pin it down. Overall, the Rocks sounded slightly warm, as if the upper bass had a bit of extra bloom. And indeed, when I listened closely to that region, it did sound particularly vivid. But when I would then concentrate on another region—the upper midrange, for example—it would sound particularly vivid. Similarly, I was never sure if I was hearing a slight liquid texture, or if it was just something my mind created when confronted with the Rocks' uniquely effortless sound.

The third area was soundstage depth. The Rocks did a great job of re-creating individual images and, via ambience retrieval, models of the original recording environments. But the models themselves, the overall size and shape of the soundstages—particularly depth—differed just enough from my expectations, or from what I hear from the Levinson No.20.6s or VTL Ichibans, to nibble at the edge of my perception. All of these amps sized individual images similarly, but the Rocks seemed to squeeze them slightly closer together, sometimes almost to the point of crowding them.

Speaker placement, room configuration, and associated gear can all affect soundstage depth, but I did a lot of fiddling and could never get the Rocks' depth to where I thought it should be. In some cases this was just a difference in perspective, as would be the case in different seats or different halls. In others, however, it resulted in small inconsistencies among all spatial parameters—image and soundstage size, image location, ambience cues, listener perspective, etc.—that prevented my system from completely "disappearing." This was a relatively minor glitch, however, and one that might not have even registered had I been dealing with a lesser piece of gear.

Summing up
The Simaudio Moon Rock monoblock amplifier is audacious, with size, power—and cost—that are over the top. Its unusual architecture defies industry norms, and it's a huge departure from Simaudio's traditional customer base and identity. But it vindicates and backs up all of this with its performance. It's simply inadequate to say that the Moon Rock excelled at just about everything I could think of to assess. It's more accurate to say that the pair of them almost always "vanished" to leave the music to exist on its own, or to describe them as a straight wire with gain—but such overused phrases don't do justice to their excellence.

The Moon Rock costs a lot more than I can afford. But even at $37,000/pair, it's really superb, and may even be "really good for the money." That wasn't the manufacturer's goal, however, and for you and me it's not the point. Simaudio set out to build an amplifier as good as any out there, and they've done it. If you're shopping in the stratosphere and choosing among the very best available, you need to audition the Simaudio Moon Rock.

95 Chemin Du Tremblay Street, Unit 3
Boucherville, Quebec J4B 7K4
(450) 499-2212