Comprehensive reviews of high-end, feature-rich hi-fi products may require 3000, 5000, even 8000 words to adequately describe the product’s performance and features. I appreciate that, as do many of our readers. Although video reviews are growing in number and popularity, in-depth written reviews will undoubtedly continue to thrive alongside. And while article length in itself has proved not to be an obstacle, a pitfall inherent to all detailed reviews is the potential obscuration of salient features or aspects of performance by protracted coverage of features and attributes of lesser import.
I became acutely aware of this as I was finishing my full-length review of the Simaudio Moon North Collection 791 streaming preamplifier, which is published concurrently with this article. I attempted to describe every noteworthy aspect of the 791 in that review, but in the end, I felt that a key point may not have been sufficiently stressed. This short article is meant to underscore that point lest it be overlooked. The 791’s unmatched combination of features and performance, as revealed in subjective listening and on the test bench, renders many less feature-rich stereo analog preamplifiers in its price range less relevant—if not obsolete.
Aspirations and limitations
An analog preamplifier should allow connections to multiple sources and provide seamless switching between them. But its primary purposes are to boost the audio signal without degrading it, as it travels from input to output, and to provide volume control. Crucially, a preamp must not introduce distortion, noise, or other unwanted artifacts into the signal, as these flaws may well become audible once amplified. It’s the quest for signal purity that compels many audiophiles to prefer preamplifiers with no tone and balance controls, which can degrade signal purity, many believe. Decades ago, an amplification ideal was hatched in the audiophile circles: “a straight wire with gain.” This oft-cited paradigm of sonic transparency and signal fidelity has been embodied in the Moon 791 to the fullest extent possible for a component that is decidedly not a straight wire.
A perfectly functional, great-sounding setup is possible with a power amplifier directly fed by a standalone DAC with a volume control. This removes the preamplifier from the signal path altogether. There are pros and cons to such a setup—I won’t delve into this matter here—but the 791 preamplifier makes a compelling case for at least its inclusion in a stereo system. The bar of expectations for a modern, high-end preamplifier may just have been raised.
The 791 scrutinized
The North Collection includes two streaming preamplifiers, the Moon 791 and Moon 891, priced at $16,000 and $25,000, respectively (all prices in USD). These two preamps share a similar appearance and feature set, but the 891 has upgraded circuitry across the board and will attract those reaching for the best (for the Moon?) whatever the cost. I suspect most users will find the 791 more than sufficient, though.
At its core, the 791 is an analog stereo preamplifier with an exceptional volume control, in both functionality and feel, and with no tone or balance controls, audiophiles will be pleased to know. It ships with the fantastic Moon BRM-1 remote control, which features a volume knob with a tactile feel similar to the one on the preamp. The 791 has three sets of analog inputs, one balanced (XLR) and two single ended (RCA), along with numerous digital inputs, including provisions for wired and wireless network connectivity. As a two-channel analog preamplifier, it has all the necessary switching capability.
The 791 is one of the most transparent preamps I’ve ever encountered. To my ears, its sonic presence was virtually imperceptible and our lab’s measurements confirmed this perception. Diego Estan, our measurements specialist, found that volume-control tracking resulted in a maximum deviation of 0.022dB between channels, which is negligible. At the default setting of 10dB of gain, crosstalk measurements at 10kHz were −145dB and −137dB for the left and right channels, respectively, indicating outstanding channel separation. Total harmonic distortion was measured at 0.00019%, which is far below audibility. A-weighted signal-to-noise ratios ranged from 120dB (referenced to 2Vrms) to 136dB (referenced to an output voltage of 20Vrms at maximum volume), which are remarkably high figures, signifying minimal noise.
Dozens of other tests conducted by Diego produced similarly impressive results confirming the 791’s position as a topflight preamplifier that stands with the best available, irrespective of price. What sets the 791 apart is that it manages to offer this stellar performance as well as a bevy of useful features. Typically, performance and features are inversely related: the fewer the features, the better the performance. The figures we obtained in our measurements of the 791 would be impressive enough for a preamplifier with only basic features; for a fully featured preamp, they are stupendous.
The 791 includes a built-in phono stage that supports moving-magnet and moving-coil cartridges, each with multiple configuration options; an up-to-date digital-to-analog converter section; and onboard streaming capability, by ethernet or Wi-Fi, through Simaudio’s MiND 2 streaming platform, which consists of a robust streaming module and a feature-rich, user-friendly controller app.
Measurements of the 791’s phono and digital sections yielded consistently superb results that left little to be desired, and this flawless performance was patently evident in my audition. You are unlikely to find an external phono preamp that outperforms the 791’s in accuracy (the appeal of its overall sound, of course, is still a matter of individual preference). Similarly, you won’t easily find a separate DAC that surpasses the 791’s accuracy and transparency even within Simaudio’s product lineup, including the standalone Moon 681 DAC. In fact, Dominique Poupart, Simaudio’s product director, told me that the 791’s digital circuitry is superior to the 681’s, and the 891’s is better still. The 791’s DAC implementation has been optimized for top performance; there’s nothing to gain by externalizing it.
For both vinyl and digital playback, the 791 can be considered a top-tier performer. Even if you intend to use only a subset of the 791’s capabilities and features—you may be committed to vinyl or listen to digital exclusively—you’ll still benefit from a top-notch phono stage or DAC, as the case may be, in a first-rate preamplifier.
I’d be remiss to not point out that one way to better the 791’s performance is to opt for the company’s top-of-the-line streaming preamplifier, the Moon 891. Dimensionally similar to the 791, albeit taller, the 891 improves on its sibling through subtle circuitry refinements to the line stage, phono stage, and digital-to-analog sections, as well as to the volume control. The resulting improvements would undoubtedly show up on the test bench, but whether they’d be discernible to the ear, given the extraordinary performance of the 791, is questionable. The 791’s noise and distortion figures, and other performance parameters, already dip below the theoretical threshold of audibility. A side-by-side comparison would be the surest way to find out.
In implementing a large set of valuable features with no apparent compromises to its performance, the Moon 791 marks an extraordinary departure from the expected norm, linking fancy features to performance penalty. In fact, the outstanding test-bench results of the 791 led Diego to write to Dominique Poupart, “Bravo on a technically exceptional product!” Diego rarely offers such commendations, and rarely do I heap such praise on a component, but the audiophile-grade 791 is exceptional: it is a straight wire with gain and it has oodles of features. Have your cake and eat it too!
. . . Doug Schneider