Solid State Preamp Reviews

Transparency is a trait we all value in a hi-fi rig, and it's a concept I've long thought I understood. A system that tosses up the illusion of a clear, spacious soundstage, on which you can hear—almost see—all of the singers and/or instruments, from side to side and, especially, from front to way, way back: that's the ticket. Still, although such transparency is a sign that you've entered the realm of fine sound, it's not an absolute requirement. Tonal accuracy, dynamic range, a certain thereness that conveys the emotional heft or delicacy of music—those things come first. Without them, the most precisely delineated soundstage is like an architect's sketch of an oil painting.

But after listening to Simaudio's Moon Evolution 740P preamplifier, I see that I've had it wrong all these decades. Those other aspects are still more important (I've been right about that), but I'd had only a partial understanding of transparency, because I've never before heard, at any length, a system that delivers the concept full-range. But now that I've heard it, I also realize that transparency isn't a mere audiophile bonus; it enriches, even transforms, all of those other qualities—tonal accuracy, dynamic range, that thereness—that excite us when a great recording sounds so close to the real thing.

But let us begin at the beginning.

Description and Design
Simaudio's 740P ($9500) is a solid-state line-stage preamplifier with a dual-mono configuration and balanced differential audio circuitry—a culmination of the Quebecois company's premier series, the Moon Evolution models, which itself is the latest chapter of their storied 35-year presence in high-end audio. Outwardly, the 740P resembles previous Moon Evolution models: the attractive, curved-edged design (available in all black, all silver, or a combination called 2-Tone); the ultrarigid aluminum case with sharp thumbscrew cones protruding from the bottoms of four triangular pillars, to reduce the effects of spurious vibrations. But there are new refinements, inside and out.

Most touted in the 740P's manual is Simaudio's fully discrete, four-stage, proprietary M-LoVo low-voltage regulator, said to produce "exceptionally fast, precise and stable DC voltage" that results in "a power supply with a virtually unmeasurable noise floor." Also designed especially for the Evolution line is an Independent Inductive DC filter, which isolates all the electronic parts in the signal path that are fed DC power. The signal path is shortened, and its impedance lowered, thanks to a four-layer circuit board—two layers for the audio signals, one for the ground, one for the power supply—etched with tracings of pure copper. The power supply, which has five stages of DC voltage regulation and extensive choke filtering, is oversize so that, as the demand for current swells, the supply of voltage dips only slightly, making possible (the manual claims) effortless dynamic peaks with no change in the music's detail, color, or character.

Simaudio's M-eVOL2 volume control comprises 530 discrete steps of 0.1dB each, with a variation of less than 0.05dB between channels across the entire volume range. Each line input is "home-theater ready," meaning that the volume control can be bypassed. A SimLink controller port allows for two-way communication with other Moon Evolution models. Oddly, I discovered that I could also use the remote control to stop, play, pause, and change tracks with my Krell Cipher SACD/CD player.

Setup
I did all of my listening through Revel's Ultima Studio2 loudspeakers. LPs were spun on a VPI Classic turntable with JMW Memorial tonearm and an Ortofon Blue Cadenza cartridge, plugged into a Nagra BPS battery-powered phono preamp. Digital discs were loaded into the Krell Cipher. Cables (single-ended from the phono, balanced from the CD player) were all by Nirvana. For a power amp, I mainly used Simaudio's Moon Evolution 860A (review in the works), occasionally switching to the power-amp section of their Moon Evolution 700i integrated amp (which I've had in my system for some time). To isolate the 740P's sound, I also plugged the 700i's preamp section into the 860A. For another comparison, and for other reasons discussed below, I borrowed a Pass Laboratories XP-30 preamp and connected it to the 860A.

The 740P's manual says that it needs 400 hours of playing time to break in fully; based on my experience, I second that advice. Simaudio also recommends keeping the 740P on at all times: Turn it off for three days, and it takes another three days to warm up again. The good news: If you turn it off for a week or a month, it also takes three days to warm back up.

Sound
In his review of the Pass Labs XP-30 line preamp in the April 2013 issue, John Atkinson concluded that that unit validated the notion that "the beating heart of an audio system is the preamplifier." I cocked an eyebrow when I read that, but after spending a few months with the Moon Evolution 740P, I'm inclined to agree. It makes sense: the signal passed through the preamp is what is amplified and converted to acoustic waves; the preamp does its work at extremely low levels that, by themselves, are nearly inaudible; any noise it contributes will be hugely magnified further down the chain. As you may have noticed from my summary, nearly all of the technical features highlighted in the 740P's manual are claimed to reduce vibrations, distortions, and noise of all kinds. Perhaps this accounts for the 740P's transparency.

Whatever the cause, with every album and song I played, I found it hard to take notes. I just sat back—or leaned forward—and soaked in the music, sometimes with an idiotic smile on my face, even if I'd heard the record a hundred times before. Finally, I tried to analyze what was happening. My first scribbled note: "All the music is breathing forth at the same time."

Six months ago, if I'd read that sentence in a review, I'd have shrugged and muttered, "Yeah, well, my system does that too." I would have been wrong. My system—an assemblage of perfectly respectable high-end components—didn't quite do that.

Take "Nuages," from Chasin' the Gypsy, James Carter's tribute to Django Reinhardt (CD, Atlantic 83304-2). In many past reviews I've marveled at how some piece of gear captured the oomph of the bass drum, the clinging of the bells, the clang of the triangle, or the distinctive strumming of each guitar, one metal-strung, the other nylon. But until the 740P, I'd never heard all of these elements in tandem; I'd never heard, at least not continuously, the rhythm of the bells playing off the rhythm of the drums, or the accordion playing off the violin, or the guitars trading fours. I'd heard the sounds, but I'd been missing something vital about the music.

What I'm describing might strike some as mere detail, and they'd be right. It is detail: detail that lives in the low-level signals, detail that most preamps (including many very good ones) smudge but that the 740P let shine through—and, in doing so, pumped blood into "the beating heart" (to riff on JA's image) not only of my audio system but also of my music.