Simaudio Moon Evolution P-8 preamplifier John Atkinson, September 2009

John Atkinson wrote about the Moon Evolution P-8 in September 2009 (Vol.32 No.9):

Back in March, I reviewed the Moon Evolution P-7 preamplifier ($6900) from Canadian manufacturer Simaudio. As you can read in the reprint of that review in our free online archives, I very much enjoyed my time with the P-7: "Beautifully made, beautiful looking, and beautiful sounding, the Moon Evolution P-7 justifiably deserves a Class A recommendation in Stereophile's 'Recommended Components.'" I also wrote that I would soon turn my attention to Simaudio's Moon Evolution P-8 dual-chassis preamplifier, but added that, "given how consistently fine the P-7 sounded in my system, it's difficult to imagine how it might improve on what its less expensive sibling has to offer."

Kalman Rubinson reviewed the Moon Evolution P-8 ($13,500) in November 2006 and was much impressed, concluding that it reminded him of Lewis Carroll's Cheshire Cat: "When the Cat is conversing, or when I use the P-8's controls, either is engaging company. Otherwise, their corporeal representations fade, each leaving behind only its most notable feature. In the case of the P-8, that was the sound of the music (and the smile on my face)."

I refer readers to Kal's review for a full description of the P-8. While basically functionally identical to the single-box P-7, the P-8 segregates all the "dirty" circuitry—control logic and microprocessor, display, power supply—in one chassis and keeps the signal-handling circuitry in a separate, "clean" chassis. The two are connected with two four-pin XLR cables, each carrying the DC voltage supplies for a single channel. A third cable, using an eight-pin Ethercon connector within its XLR shells, carries the source, volume, and setup information from the control box to the audio box.

The circuitry of the two preamplifiers is fundamentally similar except for the continuously rotating volume control. Whereas the P-7 implemented its volume control with a circuit Simaudio calls M-eVOL, which gives 1dB steps between settings of "0" and "30," and 0.5dB steps between "30" and the maximum setting of "80," the P-8's more sophisticated M-Ray volume-control circuitry uses pairs of close-tolerance R-2R resistor ladders with a total of 530 steps: of 1dB from 0 to 30dB, and of 0.1dB from 30 to 80dB.

I used the P-7 for several months, and then the P-8 for almost as long. I then spent a long weekend swapping between the two preamps, after first ensuring that their levels were precisely matched.

It was the strangest thing. In side-by-side comparisons, I was hard-pressed to hear any differences at all between the P-8 and the half-the-price P-7. Both had the same slightly forward sound when compared with the darker-hued Mark Levinson No.380S; both sounded more robust than the somewhat ethereal Parasound Halo JC 2.

But listening to the P-8 for extended periods, it offered a palpability, a solidity to the recorded soundstage, that I didn't experience with the P-7. During the review period I mastered Live at Otto's Shrunken Head (Stereophile STPH020-2), the latest CD from Bob Reina's electric jazz group Attention Screen, and both preamps faithfully reproduced the images of the musicians crowded onto the Manhattan club's tiny stage. Soundstage width and depth were identical, but the individual acoustic objects within that stage had more of a three-dimensional feel through the P-8—even when, as in the cases of the bass, guitar, and electric piano on this CD, those objects actually represented loudspeakers! Such details as the way drummer Mark Flynn's toms in "Ice Crushing at All Speeds" could be heard to "light up" the walls of the club were more readily perceived, almost as if the ear-brain was having to do less work to create the illusion of a soundstage lying between, behind, and perhaps above the speakers.

Technically, the two preamplifiers measured very similarly. Both had wide bandwidths and superbly linear circuitry, though the P-8 had an even lower noise floor than the already deathly quiet P-7. Could that have been the reason, at least in part, for the P-8's admittedly subtle but, once heard and learned, significant superiority? I must admit that I don't have a clue. Except that, before the Moon Evolution P-8, the finest-sounding preamp I'd used in my system had been, without a doubt, Ayre Acoustics' KX-R ($18,500), which Wes Phillips reviewed in October 2008. Like the P-8, the Ayre, had that degree of image palpability—and an astonishingly low noise floor. And the tubed Convergent Audio Technology SL1 Renaissance that Bob Deutsch raves about in the November 2009 issue also has very low levels of background noise.

This image palpability, of course, has long been held to be the prerogative of tube preamps, though they don't always have low noise, and older designs often had a somewhat forward midrange that you either loved or were annoyed by. Nevertheless, it was to obtain that palpability that, back in 1984, I spent the money I'd planned to use for a down payment on a car on a tubed Audio Research SP-10 preamplifier (which I still have, though I haven't used it in years). These days, the best solid-state preamps, such as the Ayre KX-R and now the Simaudio Moon P-8, at least equal tubed preamps, and perhaps even exceed their performance, in an area that used to be the exclusive preserve of tubes.

The brief period of overlap during which I had the Meridian 808i.2 CD player, the Musical Fidelity 750K Supercharger monoblocks, the Revel Ultima Salon2 speakers, and the Simaudio Moon Evolution P-8 preamplifier was, I think, the best sound I have experienced in my current room. First the Musical Fidelitys had to go back to the distributor, then the Revels had to be forwarded to a reviewer for another magazine. And now that I've written this Follow-Up, the Simaudio P-8 will soon be on its way back to Canada. But as I write these words, with Attention Screen playing on the Meridian and a Simaudio Moon Evolution W-7 amplifier driving the Acoustic Energy AE1 Mk.3 Special Edition speakers I will be reviewing in the November issue, the P-8 is still working its special magic on the soundstage—and the music!—John Atkinson

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