Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click here.
Ten years ago to the day, my review of Simaudio’s Moon Evolution 740P preamplifier was published on this site. I was so impressed with the 740P that I’ve kept it in my system after the audition period until earlier this year. What better time, I thought, to review its recently released successor, the Moon 791 preamplifier, part of the company’s new North Collection. For a complete picture, though, a brief overview of the 740P is in order.
The 740P was strictly a line-stage preamplifier. It provided input switching for balanced and single-ended analog sources, gain for all incoming signals, and volume control. Although its functionality was limited, its performance of those functions it did have made it stand out. It was well built, and it was dead quiet. Even with the volume control wide open, it would add almost no hiss, noise, or distortion to the audio signal. Simaudio employed its M-eVOL2 volume-control circuitry in the 740P, which had accurate left- and right-channel matching and fine-grained volume control: 530 steps, with 0.1dB increments at higher levels. Also notable was the volume knob itself. It was reassuringly heavy and turned with just the right amount of inertia.
The 740P was a great preamplifier. It’s no wonder it stayed in Simaudio’s lineup for so long. Its replacement, the 791, arrived earlier this year along with the other components in the North Collection. The first thing I noticed was the significant uptick in price: the 740P was $9500 just before it was discontinued; the 791 is $16,000 (all prices in USD unless noted otherwise). But with that disparity in price came the promise of better performance and a larger set of features. Buckle up. There’s much to cover.
Physical attributes and display
The 791 is very similar to the 740P in both appearance and size—4.03″H (with footers) × 18.95″W × 17.66″D. Its all-metal chassis construction makes it heavy for a preamp (over 30 pounds) but super-sturdy. As with the 740P, the 791’s panels are mostly powder-coated matte black, with solid-aluminum accents: corner posts, a top plate engraved with Simaudio’s logo, and two front-facing “cheeks,” as Simaudio calls them. Simaudio deliberately kept cosmetic changes to the minimum. Earlier this spring, during a video shoot of the North Collection for our YouTube channel, Dominique Poupart, Simaudio’s product director, told me that with the North line, they wanted to update the company’s signature styling, not abolish it.
Except for the well-liked volume knob, according to Poupart, not one part of the 740P has been carried over to the 791 unchanged. Of these changes, most noticeable are the sloped tops on the cheeks and middle-section of the front panel, which give the 791 a bit of a sporty flair. Those cheeks have also been extended to curve around the corners. Another noticeable change involves the conical metal footers both models are fitted with. On the 791, these footers embed a polyurethane-based suspension system and terminate with small plastic bumpers, providing a softer footing and better mechanical isolation from the surface it rests on.
The front and rear panels have also changed, which hints at what’s new inside. For example, the 740P’s red-dot LED display has been replaced by a 4.3″ color display. Among other things, the display shows the input selected and volume level, just as the 740P’s display did, but it also shows the album graphics and track information on the MiND 2 streaming input. (Simaudio’s MiND 2 platform—Moon intelligent Network Device—consists of a streaming module and Controller app. More on this later.) The 740P did not have network connectivity nor streaming capability.
As with the 740P, the screen is also used to program the 791’s numerous configuration options via an interface that works in conjunction with the volume knob and front-panel pushbuttons. The 791’s setting options are much more extensive than those of the 740P were, and the new, larger display makes it easier to navigate through them. The option to rename inputs allows their identification to be more intuitive on the screen and in the MiND Controller app, and the option to trim the list of selectable inputs to only those used makes it easier to scroll through them.
The onscreen interface is also used to set up a Wi-Fi network connection if you hate running long cables, as I do, and to download and install firmware updates as Simaudio rolls them out. (That happened during the audition period.)
Circuitry and volume control
The 791 uses fully balanced circuitry to achieve the lowest noise and distortion, as the 740P did. Simaudio claims signal-to-noise ratios of 120dB for the line-level analog inputs and 125dB for the digital inputs. Total harmonic distortion plus noise and intermodulation distortion for analog and digital inputs are rated at only 0.0004% and 0.0003%, respectively. The 740P’s default 6dB of overall gain has been increased to 10dB in the 791, with a negligible increase in noise, according to Poupart.
Like the 740P, the 791 allows adjustment of gain of individual inputs for a consistent volume level between different sources. Adjustment of gain can also be used to optimize the performance of the 791 and power amp it is driving as a system, in terms of noise and distortion. The gain offset range is not specified, but it was measured by our electronics-measurements specialist, Diego Estan, to be from −6dB to +14dB. Two other settings are available that are essential to system safety: startup volume and maximum volume. A home-theater bypass mode, which relegates volume control to a separate A/V receiver or a home-theater processor, is also available.
Although the 791’s volume knob is the same as the 740P’s, its functionality and the circuitry underlying it (now called M-VOL3) have changed. As mentioned above, the 740P’s volume control had 530 steps: from 0dB to 30dB steps were 1dB increments, and from 30dB to 80dB they were 0.1dB increments when the volume knob was rotated slowly, 1dB increments when rotated quickly. The 791’s volume control has fewer steps, only 140, with coarser increments at higher levels: from 0dB to 20dB steps are 1dB increments, from 20dB to 80dB they are 0.5dB or 1dB—again, depending on how quickly the volume knob is turned. I asked Poupart what the reason was behind this change. He explained that although the 0.1dB increments appealed to precision fanatics, to most users, the change was too subtle. They couldn’t tell the difference. Diego concurred. When he tried the 740P in his system, the 0.1dB step was too small for him, too, to discern. I, for one, really liked it. I’m a precision fanatic, I guess. But I must say that the 791’s 0.5dB step, though not as precise, works perfectly fine. I never found myself unable to set the proper volume level.
The 791’s volume control is paralleled on the accompanying remote control, Simaudio’s new BRM-1. This remote connects to the 791 via Bluetooth. It goes into a standby mode when not in use but wakes up when touched, and it is charged through a USB-C port on its underside. The volume knob on the BRM-1 is in fact a smoothly rotating ring with a great tactile feel that mimics the behavior of the knob on the front panel (though it lacks its free-spinning feel). This ring encircles a fixed touch-sensitive display that shows centrally the volume level or, alternatively, the active input. A short tap toggles between volume and input modes. A long tap makes accessible a few additional functions. Arranged peripherally on the display are four virtual buttons that serve common functions: play/pause, forward, back, and mute.
The BRM-1’s compact, oval shape fits nicely in your hand and looks—and is—light years ahead of the pushbutton-festooned wand-type remote that came with the 740P. Simaudio isn’t the first to implement a volume knob on a remote control, but the BRM-1’s feels and works better than any other I’ve tried.
The 791’s rear panel is packed. On it, you’ll see a whole slew of digital inputs that the 740P didn’t have—the 740P didn’t have a built-in DAC; the 791 does. It is for this digital section and the MiND 2 platform and network connections that Simaudio calls the 791 and its bigger sibling, the 891 ($25,000), network preamplifiers (we call this category streaming preamplifiers).
The back-panel array of digital inputs comprises two coaxial S/PDIF (RCA), two optical S/PDIF (TosLink), one AES/EBU (XLR), one USB Audio (Type B), and one HDMI ARC. Two ethernet (RJ-45) ports allow wired connection to a router or a NAS device. For wireless connectivity, Wi-Fi and Bluetooth are supported (two antennas are supplied, which attach to the back panel). PCM and MQA up to 384kHz and DSD up to quad-rate are supported on the USB Audio input and through the MiND 2 streamer. The other connections support lower-resolution playback, as detailed in the owner’s manual. It’s also possible to connect an external storage device to the USB-A port on the rear panel.
The 791’s digital section is no mere afterthought. It incorporates Simaudio’s MDE‑2 DAC technology, which is based on an ESS chipset and expands on the developments of the company’s well-regarded 680D and 780D v2 streaming DACs (discontinued; $10,500 and $18,000 when available). It combines ESS Technology’s flagship DAC chip, the 32-bit ES9038PRO, with a custom FPGA that provides precise reclocking. The digital section in the 791, Poupart told me, is superior to the standalone Moon 681 network player / DAC, also in the North Collection ($12,000).
The 740P had three sets of single-ended (RCA) and two sets of balanced (XLR) inputs; the 791 has only two sets of single-ended (RCA) and one set of balanced (XLR) inputs, which is probably enough in most setups. Where Simaudio upped their game is with the 791’s phono stage, which is compatible with moving-magnet (MM) and moving-coil (MC) cartridges. The phono stage is linked to the left pair of single-ended analog inputs (a ground post is within an inch of the pair) and can be configured as either MM or MC through the onscreen menu system. If you don’t need the phono stage, you can configure that pair for line-level analog sources.
The 791’s phono stage is factory set for standard gain, impedance, and capacitance for each cartridge type. For example, 40dB of gain for MM and 60dB for MC. These default settings are shown in the Basic mode of the setup menu for the phono input. In the Advanced mode, they can be changed, as can the equalization curve. Like its digital section, the 791’s phono stage is well designed and well executed. Indeed, Simaudio has been lauded over the years for the performance and configurability of its phono stages.
An important difference between the 740P and 791 concerns fixed and variable outputs. The 740P had one pair of variable balanced (XLR) outputs and two pairs of single-ended (RCA) outputs, one fixed level and the other variable. The 791 simplifies that: it has one pair of balanced (XLR) outputs and one pair of single-ended (RCA) outputs that are independently configurable to be fixed level or variable. Most people use variable output; I do too. But to those who intend to use the fixed-level output, a word of caution: setting fixed-level output means you’re outputting a signal with the volume all the way up, so be sure to lower the volume on the connected device first. You could blow your speakers out otherwise.
Finally, like the 740P, the 791 has XLR-type connectors to add an outboard power supply. Separating the power supply from the other circuitry can potentially increase performance. But given how well the 791 performs, I doubt this would improve its performance appreciably.
The system I set up the 791 in was described in last month’s “System One” column, which focused on the Estelon Aura loudspeakers. At the time I was writing that article, I considered installing the 791 in my reference-room setup, but ultimately decided to keep it in my living room, where I have a turntable, two amps, and a good Wi-Fi connection and could better put it through its paces. My forthcoming audition of the Moon 761 power amplifier will likely take place in my reference room, where it could be adequately challenged by the larger space and different pairs of speakers.
As I described in my “System One” article, I set up the 791 with two source components from Pro-Ject: a CD Box S3 CD player and an X1 turntable with a Pick it S2 moving-magnet cartridge. Speaker cables were the Nirvana S-L, analog interconnects were the XLO DNA, and power cables were the stock ones for all components. Everything was plugged into a Shunyata Research Venom PS8 distributor, which was connected to the wall outlet via a Venom HC power cord.
I used an NAD Masters M23 power amplifier ($3750) to see how the 791 performed with another amplifier besides the 761. The M23 has three user-adjustable gain settings: Low (19dB), Mid (23.9dB), and High (29.2dB). I used the Mid setting. I connected the preamp to the M23, and later to the 761, with balanced XLO DNA cables. I also used a Furutech coaxial cable to connect from the CD Box S3’s coaxial output to one of the 791’s coaxial inputs so that I could use the CD Box S3 as a transport.
One more thing not mentioned in my “System One” article has to do with the importance of having the 791 connected to a network on initial setup, by wire or wirelessly, even when music streaming is not intended. One reason is that Simaudio regularly pushes out firmware updates via the internet. These updates may add new features and often improve performance and fix bugs; they are important. Another reason is that until a network connection is established, the 791’s Wi-Fi circuitry continuously sends out a beaconing signal. This behavior can’t be disabled.
Before assessing the sound quality of digital playback with the 791, I first wanted to evaluate the functionality of its MiND 2 streaming software with online streaming services and locally stored music files.
When I launched the MiND Controller app on my Android phone, it immediately found the 791, which had already been connected to my network. When I tapped the 791 icon, I was presented with various streaming options: Spotify, Qobuz, Tidal, Deezer, and HighResAudio. I selected Tidal, the streaming service I currently subscribe to, and logged in. There were podcasts and internet radio stations aplenty to choose from as well, but my critical listening of streaming music was through Tidal, which I found consistently reliable. I imagine Qobuz, which is also popular among audiophiles, would have worked equally well.
I quickly learned that aside from setting up Wi-Fi through the MiND Controller app, you can also control the volume and activate muting with it. The MiND app also supports gapless playback, allows the creation of playlists, and shows album art prominently—within the app itself as well as on the 791’s screen. As I mentioned, MiND 2 will support PCM and MQA up to 32-bit/384kHz as well as up to quad-rate DSD. So, if you intend to mostly stream from one of the supported services, Moon’s MiND 2 platform will serve you well. It is completely integrated into the 791.
Local-file playback didn’t go so swimmingly. I plugged the portable solid-state drive (SSD) where my music library is stored into the USB-A port on the back of the 791, but the MiND 2 software didn’t seem to recognize it. I don’t know why. The 791 owner’s manual does say, though, that “compatibility is not guaranteed with every brand and model of USB drive nor with every file system” and that “for the best performance and navigation experience, use a DLNA server on a UPnP device to share the files over a network.”
However, MiND 2’s primary purpose is to stream from a NAS and online music services. The MiND Controller app can even blend tracks from multiple local and online servers into a single play queue. And the MiND 2 module is Roon Ready. To test this, I plugged my SSD drive into a computer running Roon server software in another room. For its features, ease of use, and the way it merges locally stored music files with streaming services, Roon is the best software for audiophiles, I believe. It’s not cheap, though: a lifetime subscription is $829.99, a monthly subscription $14.99. It also requires a reasonably powerful computer to run on.
At this point, both the 791 and the computer running Roon were connected to the network via Wi-Fi. When I opened Roon to play some music files from my SSD, the 791 was immediately identified as a Roon Ready device. Selecting it switched the 791’s input to the MiND streamer, as was shown in the MiND Controller app.
I first played selections from my 16-bit/44.1kHz WAV rip of Bruce Cockburn’s The Charity of Night (True North Records), which worked without issue. Next, I played a 24/96 FLAC remaster of the Tragically Hip’s Road Apples (Universal Music Canada)—again, without any difficulty. I then thought I’d try to mess with the 791’s MiND playing a 24/192 FLAC file, a version of Carpenters with the Royal Philharmonic Orchestra (A&M Records / Universal Music Enterprises). A substantial bandwidth needs to be sustained at this resolution; the 791 and Roon server were two floors apart from each other, in areas where the Wi-Fi signal is weak. Playback was fine yet again. I also played a DSD64 (single-rate DSD) version of the Holly Cole Trio’s Girl Talk (Alert Records / 2xHD) without fault. With that album, I noticed that both Roon and the MiND Controller app were indicating that a native DSD64 DFF file was being transmitted and received, verifying that the MiND 2 software does support DSD. Unfortunately, I didn’t have a DSD256 (quad-rate DSD) file on hand and couldn’t test the system’s handling of this high-resolution audio format.
That the MiND Controller app showed the DSD resolution is one indication of the tight integration of Roon, MiND 2, and the 791. Another is that Roon also transfers each album’s graphic to both the MiND Controller app and the 791’s front-panel display. This integration goes beyond the sharing of playback information: a volume-level change in Roon is synced with the app and the 791 with minimal lag. I also noticed that the track-skip function on both the BRM-1 remote control and within the MiND Controller app was synced to the one in Roon. Finally, I discovered that when the 791 is on standby, an audio signal from Roon will kick it back to life and automatically select the MiND input if another is selected, which is all very convenient.
If you’re just going to stream from any of the supported services, MiND 2 would suffice. But if you want the ultimate in digital streaming and local-music playback, Roon is easy to recommend.
One outstanding quality of the 740P, as I mentioned, was its quietness. So naturally, the first thing I did once the 791 and 761 amp were hooked up and powered was to select the balanced analog input, which wasn’t connected to any source, turn the volume wide open, and put an ear to a tweeter. What I heard was barely audible even within an inch or two of the tweeter. Repeating this experiment with the right (non-phono) single-ended analog input resulted in similar noiselessness.
When I swapped in the NAD M23 amp later and tried this again, I found the noise level to be just as low. (To test the 791’s contribution to noise in this setup, Diego suggested that I turn it off. This had practically no effect on noise level. Evidently, the 791 was adding almost no noise.) When I tried this with the phono input, which was configured for a moving-magnet cartridge with the standard 40dB of gain, I did notice more noise with both amps. But that’s what you’d expect with such massive gain—40dB is a hundredfold boost to the audio signal! Still, for a phono stage, it was very, very quiet.
The 791’s phono stage was also exceedingly neutral, something I noticed the moment I played Fleetwood Mac’s Rumours (LP, Warner Bros. BSK 3010) and then again in some of my other regular audition albums. From the bottommost bass to the highest highs, no part of the audioband seemed heightened or abated. Every album sounded perfectly balanced. Being so clean and quiet, the 791’s phono stage recovered every last nuance from those old vinyl pressings—and every imperfection the Pro-Ject X1 turntable was able to pick up—presenting it all in bold relief.
Listening intently to these records, I had a nagging feeling that my Pro-Ject X1 turntable, a modest rig costing $1400 CDN, was hopelessly outclassed by the 791’s phono stage. I felt that this very quiet phono stage and the 791’s nearly silent line-stage section could potentially reveal much more sonic detail than the Pro-Ject X1 could provide. I couldn’t escape the conclusion, as I intimated in my "System One” article, that I now need to find a turntable that is a better match for my system. I’m on that journey right now, evaluating the 791 with higher-quality turntables and better cartridges. Updates on this search will likely be covered in a “System One” column early next year.
Digital playback was another story. I felt no sonic limitations regardless of whether I was streaming from Tidal or playing music files from my SSD via Roon. The sound was neutral throughout the audible range, which is what you’d expect from any well-designed digital source, and it was spectacularly clean, providing the clarity for every sonic detail to flow unimpeded to the speakers. The exceptional clarity of the 791’s digital section and purity of sound lent beguiling immediacy to the presentation.
One of my favorite evaluation tracks is “Pacing the Cage,” on Bruce Cockburn’s The Charity of Night. Whenever I listen to this track, I first focus my attention on each of its three parts: Cockburn’s vocals, his acoustic guitar, and Rob Wasserman’s bass. With high-quality systems, these parts jump out distinctively at specific places on the soundstage. They certainly did with the 791, whether it was driving the 761 or M23. The next thing I listen for is how well delineated the performers are on the soundstage and whether I can hear the subtle acoustic cues of the recording venue. With the 791 I could. But what I also noticed was how pure the sound was, mostly in the highs, to a lesser degree in the midrange. Cockburn’s guitar had all the sparkle I’ve come to expect to hear and none of the brittleness I’ve heard with some other systems. I hesitate to use the word smooth to describe what I was hearing because to some audiophiles that implies a high-frequency rolloff or a glossing over of details—there was none of that. Smooth, though, aptly describes the dazzling sense of clarity and cleanliness the 791 imparted to this music.
The high level of detail that the 791 was able to reproduce is something I wrote about in my “System One” article: “As we played each song, we focused on [Lana] Del Rey’s voice and marveled at the level of detail that issued from the Auras. We were able to hear the subtlest of vocal inflections and the various studio tricks that are used to enhance the emotive power of the performance. We continued with other songs, and I realized that I had never heard digital playback in my living room sound so detailed, so revealing.” By no small margin, those recordings sounded better than with any other system I had had in that room or even in my reference room. The 791 can’t take all the credit for that sound quality—the amp, speakers, and connections were all top-class—but it contributed to it significantly.
Hearing such detail from digital prompted me to pull out my CD of Blue Rodeo’s 1989 Diamond Mine album (WEA CD 56268). I loaded it into the CD Box S3, using it as a disc transport and letting the 791 convert the bits. At this point, it was driving the M23 amp. This original Canadian release of Diamond Mine includes an unusual, unlisted minute-long track (labeled “Percussive Piano” in other releases), which I’ve used for years to test components’ ability to reveal detail. “Percussive Piano” contains nothing more than light tapping on the body of a piano by then-keyboardist Bob Wiseman and a sparse sprinkling of keystrokes. It is very quiet, almost remote, as though part of the background (a 2012 album remaster brought the level up considerably); but therein lies its utility. Back in the 1990s, some CD players and DACs were so poor at revealing low-level detail that this track often sounded like a minute of silence at normal volume levels. You’d have to turn the volume up full blast to hear anything. As players and DACs got better, those percussive piano taps became more perceptible, and when players and DACs got really good, you could hear the sounds in between—that’s what the 791-M23-Aura system allowed me to hear. With practically no obscuring noise from the electronics, I could hear everything clearly even at low volume levels.
I’ve been touting repeatedly the 791’s veritable lack of noise. But what about its sound? Well, it turns out that it lacks that too. Whether an analog playback or digital, the 791 asserted no sound, coloration, or character of its own. It simply got out of the way and passed the music signal through, which is exactly what a top-drawer preamplifier is supposed to do. It just happened to do it with a considerable number of bells and whistles attached.
The 740P was the right kind of audiophile preamplifier for its time. High-resolution music streaming had not yet pervaded the audiophile sphere, DAC and digital-connection technology was changing frequently, and no one knew where the vinyl resurgence was heading. To an audiophile back then, a topflight line-stage preamplifier made sense. A phono stage, DAC, or streamer, if needed, could always be added as separate components.
The feature-rich Moon 791 makes sense today because hi-rez music streaming is prevalent among audiophiles, DAC and digital-interface technologies have matured, and vinyl seems to be here to stay. Simaudio took the high-performance, low-noise, no-distortion 740P, tweaked its line-level performance to perfection, and built on it, adding a top-tier phono stage, DAC section, and streaming module, as well as a host of digital wired and wireless connections. These added capabilities mustn’t be taken lightly nor assumed to be easily surpassed. In particular, don’t expect to find a standalone phono stage or DAC, at any price, that will outperform those built into the 791.
Despite its phono stage, digital section, and wireless connectivity, features that are known to interject noise into a system and that the 740P lacked, the 791, from what I could tell, is at least as quiet as the 740P was. That it manages to provide greater gain than the 740P did without incurring line-stage performance penalty is commendable. Although considerably more expensive than the 740P was, the Moon 791 will appeal to the discerning audiophile who wants an uncompromised preamplifier that could easily handle today’s playback needs and those in years to come.
. . . Doug Schneider
Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click here.
- Speakers: Estelon Aura.
- Turntable: Pro-Ject Audio Systems X1 with Pick it S2 cartridge and Connect it E cable.
- CD player: Pro-Ject Audio Systems CD Box S3.
- Amplifiers: Simaudio Moon 761, NAD Masters M23.
- Speaker cables: QED XT25, Nirvana Audio S-L.
- Analog interconnects: XLO DNA.
- Digital interconnect: Furutech μ-X Ag coaxial.
- Power cord: Shunyata Research Venom HC.
- Power distributor: Shunyata Research PS8.
- Acoustical treatments: BXI Sound Absorber panels (20), Tönnen Sound panels (2).
Simaudio Moon 791 Streaming Preamplifier
Warranty: Ten years, parts and labor.
1345 Rue Newton
Boucherville, QC J4B 5H2
Phone: (450) 449-2212