Simaudio MOON 371 Network Player & Amplifier

Stephen Dawson
Simaudio MOON 371 Network Player & Amplifier

Canadian high fidelity equipment maker Simaudio has been producing high quality gear for decades. These days you’ll see the brand as Moon, Simaudio Moon or Moon by Simaudio. Doesn’t matter, really. What matters is that entry-level Simaudio Moon starts, quality-wise, at where many brands stop, and goes up to pretty much as good as it gets.

Within this range, the Simaudio Moon “Compass Collection” collection is new, middling affordable (for high end gear), and at this point consists of just one product, the Simaudio Moon 371 Network Player and Amplifier.

To put that another way, the 371 is an integrated amplifier with a network streamer built in.

tl;dr

  • 1 x line level stereo analogue input (RCA); 1 x phono input (RCA – MM/MC switchable); 1 x balanced stereo analogue input (XLR)
  • 1 x optical digital audio input (TOSLINK); 2 x coaxial digital audio inputs (RCA); 1 x HDMI eARC input; 2 x Ethernet; 1 x USB Type-C (Host), Wi-Fi
  • 1 x stereo analogue pre-amp output (RCA), speaker binding posts, headphone (6.25mm)
  • Rated power: 2 x 100 watts into 8 ohms, 2 x 200 watts into 4 ohms
  • Digital signal support: PCM up to 32-bit, 384kHz, DSD up to 4x (DSD256)
  • Network support: Spotify Connect, TIDAL Connect, Qobuz Connect, Apple Airplay, Roon Ready
  • 170mm colour display
  • 1 x 12V trigger out
  • Includes remote control, power cable
  • System software: Moon 371, 1.2.5; MiND, 2.6.0; RC Interface, 1.1.1; Auxiliary microC, 1.1.2
  • Dimensions: 429mm wide by 87mm tall by 385mm deep; 9kg
  • Warranty: 10 years!
  • Verdict: The Simaudio Moon 371 is a superb-sounding integrated amplifier with a well-designed streamer and the bonus of both moving magnet and moving coil phono support
  • $11,999
  • Available at fine high fidelity retail outlets, and direct from distributor's retail division here.

A bit more about the Simaudio Moon 371

The Simaudio Moon 371 is a fairly compact unit. It adopts the usual dimensions of a high-fidelity bit of kit, so if occasion requires you can place it neatly atop a CD player or such.

(I’ve been to many a high-fidelity demo – including by Simaudio – in which the power amplifier is underneath some other component. No. Not a good idea. The 371 has heatsinks down the side and didn’t run particularly hot, but you never know. Integrated and power amplifiers should always be placed on top.)

It’s especially compact when you consider that it offers a true 100 watts per channel into 8 ohms, and 200 watts into 4 ohms. That seems to be a hallmark of Moon products: the rated 4-ohm power output is double the rated 8-ohm output. Any amplifier ought to be able to do this, but few do. It requires a more capacious power supply, which is more expensive.

While we’re talking about the power amplifier, I should mention that in some senses it is a classic Class A/B design. But in addition to the usual quality inclusions you’d expect at this price point, such as plenty of capacitance and such, there’s a new technology that has trickled down from Simaudio’s more expensive amplifiers. It’s call Moon Distortion-Cancelling Amplifier (MDCA). Instead of using global, or even stage-by-stage, feedback to reduce distortion, it uses a parallel signal path from the start of the analogue signal (ie. at the analogue inputs or immediately after the DAC) to a comparator at the speaker outputs, and creates a difference signal which it feeds back in just before the output stage but, crucially, after the gain stage. Normal feedback systems require a delicate balance. You need a bit to manage distortion, but too much emphasis on that and its presence becomes apparent with audible smearing of the sound. Simaudio says that MDCA avoids that.

It certainly has specifications that seem to take advantage of it: total harmonic distortion at full power – 100 watts – is rated at an incredibly low figure for a power amplifier, 0.003%, while the signal to noise ratio is specified at 108dB. Those are truly impressive numbers. In addition, the damping factor is a very high 425. That is a kind of inverse measure of the amplifier’s output impedance. The lower the impedance, the better control that the amplifier exercises over the physical movement of the speaker components. Simaudio says that MDCA helps with a higher damping factor.

Around the front, the unit is smooth and simple. There’s a colour display (not a touch screen) in the middle, around 170mm on the diagonal. To the right is a large volume knob with a nearby 6.5mm stereo headphone socket, and to the left is a column of six push buttons. Combined with the menu system, these switches and knob are plenty to control everything. You also get a mid-sized IR remote control which adds quick access to three Internet radio presets. You set those up using Simaudio’s MiND (Moon Intelligent Network Device) app.

On the back there are two Ethernet ports (or you can use the built-in Wi-Fi), HDMI eARC, one optical and two coaxial S/PFIF digital audio inputs, a USB-C for plugging in memory containing music files, one unbalanced and one balanced set of analogue inputs, and one set of phono inputs.

The phono inputs support both moving magnet and moving coil cartridges. There’s an option in the setup menu to switch between the two so they have appropriate input characteristics.

The MiND app is available for iOS and Android, and in addition to the network stuff, it also controls the amplifier: volume, input selection and so on.

Listening to the Simaudio Moon 371

Review equipment:

I used the Moon 371 with all the different sources, plus an external DAC (fed using the XLR inputs) to cater for a couple of other digital gadgets. With everything it sounded simply first class. The control over bass on the Contour speakers was excellent. These speakers are lowish in sensitivity and only four ohms in impedance, so they do appreciate a quality amplifier with plenty of power on tap. The 371 filled that job perfectly.

I did most of my vinyl listening with the Technics turntable, but I switched over to the Thorens just as I sat down to write this section. Since you have to go into settings to change the phono input from moving magnet to moving coil, switching isn’t something you do all the time. My main interest was making sure that the extra gain didn’t start introducing audible noise. That’s what I went there for, but I stayed because I was instantly entranced. I’d popped the album Moanin’ by Art Blakey and the Jazz Messengers onto the platter and span it up. This album was recorded in 1958, or nearly 68 years ago as I write. Originally released on Blue Note, the version I have is a recent rerelease on Jazz Images.

I stayed – winding up the volume to a thoroughly encompassing level – and just sank into sheer musicality, texture and multidimensionality of the way this music was delivered. Being a modern repressing, it has probably passed through some kind of digital pipe along the way to the current version, but if so it has not put any barrier up to the quality of the sound. As always, it had me wondering why it took more than a decade for rock and pop recordings to begin to approach the recording quality that marked late ‘50s jazz.

Anyway, I’ll make a prediction: if you buy this amplifier and like vinyl, you will not find any need to fork out for an external phono preamplifier. You’re going to have to spend an awful lot of money to find one that sounds better.

Oh, also, with it wound up to extremely satisfying levels, there was no audible noise from the MC preamplifier.

Digital and Streaming

I did a quick check of the kind of digital filter the Moon 371 uses when converting 44.1kHz content to analogue. 44.1kHz stuff is what constitutes the great bulk of what almost everyone listens to, and it is also the format for which a good filter is most critical. Looking at the broadband frequency balance and impulse performance, it was clear that the unit implements a “sharp” filter, with minimum phase selected. A sharp filter provides the most even frequency response, with no roll-off in the top octave, and also eliminates virtually all ultrasonic content. I’ll always argue it is the most accurate of the filters. The minimum phase choice provides a slightly lower latency (delay), as evidenced by the so-called “ringing” all occurring after the impulse. In practice, this makes no difference at all to the sound.

The digital content I played was from CD, Spotify, TIDAL and a range of local music files, mostly from my Synology server, but also from USB. First, I should note that all these sources sounded identical, so long as the same music file was used on each. Second, I should note that the Moon 371 played, well, everything! I have a USB stick with just about all modern formats: FLAC and Apple Lossless in a range of sampling frequencies, DSD and even MP3. Got some 24-bit 384kHz PCM music? No worries, this unit will play it perfectly from USB or your local server. Direct Stream Digital? Easy. And not just SACD-like DSD64, but also DSD128 and DSD256. I’m fairly confident they were playing through in native format. The MiND app you use to control the amplifier indicated as much.

I used the USB successfully with a drive in FAT32 format, but my 2TB exFAT drive wouldn’t work. I use exFAT for easy compatibility with both Windows and macOS. However, if you’re a Windows-only person, then Simaudio says it’s compatible with NTFS (up to 256TB!). Also with EXT2/3/4, used on Linux.

Oh, if you still have any MQA tracks, you’ll be pleased to know that the Moon 371 unfolds them all the way up to 352.8kHz.

Right now as I’m writing this section, I’ve got a playlist of Blue Coast tracks playing in standard DSD64. These are acoustic numbers from a range or artists recorded natively in DSD by the label. If a 1958 Blue Note Jazz recording is stunning, a 2010-ish Blue Coast DSD recording is as lifelike as it’s possible to get. It’s not like being there, because being there would be a lesser experience. After all, you’d likely have to put up with other people in a venue.

For a change of pace, I streamed the Rage Against the Machine debut album losslessly from Spotify, using Spotify Connect. (You can also use any DLNA-compatible app if you have a preference.) Again, loud is the way to listen to this, and the driving performance was absolutely first class. I spent weeks listening to all manner of music, including a bunch of Deutsche Grammophon classical CDs I’d picked up at a second-hand shop. That label tends towards a brightness that sometimes verges on thinness. But with the Moon 371 decoding the signal and amplifying, they sounded surprisingly rich and full-bodied.

A word on the MiND app. I first used it probably eight years ago when I was reviewing a very expensive standalone Simaudio Moon DAC/streamer. Back in those days brand-based streamer control apps were very hit and miss. I had a Denon streamer at the time, and I ended up using a third-party DLNA app because the Denon one just didn’t work properly. But what a big company like that couldn’t achieve, Simaudio did handily. The MiND app worked on my Android phone and iPad flawlessly, never missing a beat. And it still does. Like all such apps, it’ll take a little while to fully master it. For example, I couldn’t find the USB port on the list of inputs. I eventually found it in the “Library” section where the servers and music streaming servers reside. But once you get used to it, it’s fast and easy to use. And, unusually, your play queue can include a list of tracks from different sources.

Headphone listening

For various reasons, I initially couldn’t put the unit into its proper place in my system. So, being impatient, I popped it onto my coffee table and used it with some of my headphones for a while, driving it (of course) via its inbuilt streamer, and with the S/PDIF output of a FiiO DM15 R2R portable CD player.

The streamer sounded fine. But what I want to focus on for a moment is the CD. Now, I’ve measured the FiiO player, and it really ticks all the boxes. Low output impedance (less than two ohms), and over 600mW into low impedance headphones, with insignificant distortion levels.

So why did the same headphones plugged into the Moon 371 sound significantly better when playing the FiiO’s digital output?

Well, it depended. I started using Focal Elear dynamic headphones, and the sound was beautifully clean, nicely detailed, but surprisingly bass heavy. Switching to Final Audio D8000 headphones, the other characteristics were retained, but frequency balance was restored to what it ought to have been.

Again, what was going on there?

Some measurements were in order. It turns out that the headphone output of the Moon 371 has an internal impedance of 333 ohms (+/-11 ohms). That’s rather high and will likely deliver a significantly varying and unpredictable frequency balance with dynamic headphones, which vary in their own impedance by frequency. That explains the bass forwardness of the Focal headphones, and the nice balance of the Final Audio ones. The latter uses planar magnetic technology, which has almost no impedance variation by frequency.

There was still plenty of volume, even with low-impedance gear. The amplifier was good for over 410mW into 300 ohms, and 141mW into 16 ohms. That equates to, respectively, 26dB and 21dB above the sensitivity specification of whichever headphones you choose to use. You’re going to have to be using remarkably insensitive headphones for that to be insufficient. I also used the low-cost, low impedance (18 ohm), low sensitivity FiiO JT7 planar magnetic headphones, and they sounded pretty great.

My hypothesis is that the 371 uses the main power amplifiers to also power the headphones, with a 333-ish ohm resistor dropped inline to make things work safely. An alternative solution would have been to have a dedicated high quality headphone amplifier, which would have added quite a few bucks, or a low-cost power amplifier chip, which would have reduced sound quality.

I like the chosen solution, but I’d suggest the use of planar magnetic headphones. Otherwise, the sound quality will be quite unpredictable.

Imperfections?

One quirk had to do with the S/PDIF inputs. For reasons that elude me, they suffered some noticeable latency. That is, the signal was somehow delayed in the electronics. This doesn’t matter most of the time, since it doesn’t actually alter the sound of, say, your CD player or whatever.

Initially I had my TV plugged into the optical S/PDIF input. I noticed lip sync issues on broadcast TV, and this was even clearer with sound effects generated by games on the PS5. I measured it, and compared with a fairly standard, good quality DAC, the delay was 200 milliseconds. That’s about the time it takes for sound to travel nearly 70 metres.

The human mind is pretty good at knitting a delayed sound with its visual source. After all, since sound is relatively slow, it is always delayed compared to vision. But even with the human voice, this starts to fail as the delay gets up beyond 100ms.

I rechecked using the analogue inputs, and there was no perceptible delay on them, as you’d expect with a fully analogue audio path. I switched over the an eARC connection via HDMI and my sense was that there was still some audio delay, but less than there had been via optical.

That aside, the only other imperfections I’d raise are related to just the occasional recording.

Very, very occasional in the case of CD pre-emphasis. Some very early CDs had their treble boosted prior to encoding, and carried a flag indicating this. A CD player is supposed to spot the flag and apply a treble cut which reverses the boost, thus lowering high frequency noise, which is the purpose of the whole rigamarole in the first place. The Cambridge Audio CD transport identifies the flag and passes it on to the downstream DAC. Some DACs act on the flag. This one doesn’t. Again, this is for very few discs. Out of my 500 or so CDs, only a couple of early classical discs have it.

The other imperfection concerns so-called “intersample overs”. This is a quite technical subject, but it concerns the possibility that an oversampling DAC might hit a hard limit when doing that oversampling, clipping the waveform. This only occurs when two PCM samples which are next to each other are both at a level greater than -3dBFS. In a traditional DAC, that wouldn’t matter so long as the analogue stage had at least 3dB of headroom. This issue is all to do with internal resampling.

Some equipment brands make a big thing of this and boast how their designs avoid any possibility of this. Some other brands – I’ve been testing a few lately – show no signs of it on my -2dBFS, -1dBFS and 0dBFS test signals. Others are fine at the lowest signal, but show flatted tops and bottoms at the other two.

The Moon 371 produced flattened ends at all three levels. Here's the test signal at -3dB with a nicely formed sine wave:

And here it is with the same signal, but at 0dBFS:

Is this an audible problem? I don’t think so. Yes, some real-world CDs are recorded at such a high level they may contain hundreds of intersample overs. But remember, that’s hundreds out of millions of samples. And in any case, such visual distortions on an oscilloscope display of a test signal, which is simply an 11,025 hertz sine wave, are manifested as harmonic distortion, with the lowest product at 22,050 hertz!

Still, Simaudio may want to look at this since some people do make a song and dance about this issue.

Conclusion

You may have gathered that I’m extremely impressed by the Simaudio Moon 371. And you’d be right. For my own purposes, I’d have liked a couple of extra inputs, but given the built-in functionality, that’s unlikely to be required by most purchasers.

What you do get is convenient, trouble-free operation, and true audiophile performance.

Plus the confidence engendered by a 10-year warranty (3 years for some mechanical parts).

Tags: Integrated amplifiers, Moon by simaudio, Network audio streamers