Reviews of Attainable Hi-Fi & Home-Theater Equipment

Reviews of Attainable Hi-Fi & Home-Theater Equipment

Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.

Longtime readers of SoundStage! Access with particularly good memories may be feeling some déjà vu right about now. Didn’t we already review the Musical Fidelity M6si integrated amplifier-DAC some years back, much closer to its release in 2014? We did.

So why are we reviewing it again? For a couple of reasons. Firstly, as I’ve mentioned in previous pieces, I’ve been on a bit of a walkabout in the integrated amplifier wilderness for the past few months now, trying to find the mythical territory of “diminishing returns.” In other words, I’m trying to quantify how much meaningful correlation there is between price and performance, features, etc. What should you expect for $500? For $1000? For $3000?

When I talk to other enthusiasts about amps they recommend, the M6si keeps coming up in conversation. So this re-review is, in a sense, my way of finding its place in the current integrated-amp landscape, given that it remains so popular.

Musical Fidelity

This also proved to be the perfect opportunity to put the M6si on the bench after beating up on it, to get some objective measurements that either support or contradict my subjective impressions.

Despite being ever so slightly long in the tooth, the M6si ($2790, all prices USD) sports a clean and modern look that isn’t likely to go out of style anytime soon. Although it’s a beefy amp—back in my day, we would have called it “husky,” although I’m still mad at J.C. Penny for ruining that word for me—it’s definitely lithe-looking, mostly due to the contrast between the black chassis and the Apple-esque matte silver of the front faceplate. The front panel also has a wonderfully symmetrical design, with a chonky and inertial level knob right in the center that seems to have been designed to pander to volume-control fetishists like myself.

Throw in a full set of input selection buttons, a standby button, a nameplate, some bevels, an IR receiver, and some blue LEDs, and that’s it. The M6si’s faceplate is otherwise unadorned. There is no screen. No headphone jack. Just minimalist elegance.

Musical Fidelity

Spin the unit around to get to its I/O connections, though, and the vibe changes from dinner party in the front to business formal in the back. The first things you encounter on this circumnavigation are the unit’s massive heatsink cooling fins, which add 2.5″ to the total width of the cabinet. The size of the heatsinks is definitely not out of proportion with the unit’s rated power capabilities: 220Wpc into 8 ohms with THD+N of <0.007% from 20-20,000Hz. But they still make a statement.

The back panel is laid out well, with nicely spaced (and dead-sexy) five-way binding posts flanking a ground post and trigger in/out ports. In addition to the stereo XLR inputs, the unit also has RCA connections for the phono stage (MM/MC), CD input, Tuner input, and two Aux inputs, one of which can be configured for home-theater bypass at the flip of a switch. There’s also a stereo line-out and stereo pre-out, both RCA. There are no optical or coaxial ins or outs or what-have-yous. The only digital input is a USB Audio Class 1.0 (Type-B) that’s clearly labeled “24-bit/96 kHz.”

Musical Fidelity

Setting up the Musical Fidelity M6si

All of this is wrapped up in a case that measures 17.32″W x 4.92″H x 15.75″D and tips the scales at 36.6 pounds. That isn’t so prohibitively heavy as to require the assistance of a friend or loved one when you’re setting up the amp, but you definitely don’t want to drop it on a naked toe. Ask me how I know.

Given the spaciousness of the back panel and its tidy organization, hookup was quick and straightforward. I don’t own a record player anymore, so the phono input went unused. I wasn’t integrating the M6si into a home-theater system, so the bypass was merely a welcomed bonus.

Musical Fidelity

I’m normally a hands-on guy when it comes to my two-channel gear, so I don’t often complain about a lackluster remote. But the one that comes with the M6si needs some work. Its tiny volume buttons disappear among the crowd of other controls, most of which are intended for use with Musical Fidelity’s CD players.

Once I had the remote sorted out, though, I started off by connecting a USB cable from my media PC straight into the back of the amp for Qobuz and JRiver Media Center playback, with my Oppo BDP-105 connected to the CD input as a backup. But I quickly noticed that the amp got noisy when I switched to the USB input.

My first assumption was that I had somehow nicked my cable and penetrated its shielding during the setup process. So I went to swap it with another cable, only to discover that a brand new shielded cable resulted in the same noise. Even with no cable plugged into the back of the M6si, its USB input was unacceptably raspy, so I switched over to my Oppo and used its USB DAC and analog outputs for the bulk of my listening.

Musical Fidelity

In addition to Sonus Faber’s new Lumina V tower speakers (recently reviewed), I also connected a pair of Paradigm Studio 100 v.5 towers to the M6si for some additional testing, in all cases relying on ELAC Sensible speaker cables for speaker-level connections.

In-depth listening impressions of the M6si

I wish I could tell you that I had some grand plan in mind when I fired up the M6si and queued up “Seven Nation Army” from the White Stripes’ Elephant (24-bit/192kHz FLAC, Legacy Records/Qobuz). But the truth of the matter is that I wasn’t quite ready to start critical listening just yet. I had just installed the amp in my two-channel listening room and was simply in the mood to listen to Jack and Meg rock out after a long workday. I was immediately sucked in, though, instantly drawn to the amp’s reproduction of the tune. So much so that I forgot to shower that day. Heck, had my wife not pestered me, I might have skipped supper.

The weird thing about “Seven Nation Army” is that its iconic bassline isn’t actually a bassline at all. It’s a guitar riff pumped through an octave pedal. That has some pretty interesting implications for the recording—namely, the fact that the fundamentals aren’t the only thing affected by the frequency manipulation; the attack of each note and the reverb are pitch-shifted as well.

Musical Fidelity

For whatever reason, the decision was made to take these artifacts and pan them hard to the left. And I’m pretty sure you could hear this, if you were paying attention, on a clock radio—assuming it’s a stereo clock radio.

The thing about a good amp, like the M6si, plugged into a good set of speakers, like the Sonus Faber Lumina Vs, is that you don’t have to pay attention to pick up on nuances and textures like that. You’re forced to contend with them. Your focus is drawn to them.

Left to my own devices, I could spend another 5000 words waxing neck-beardedly about all the little details locked away within “Seven Nation Army” that the M6si deftly unlocked. But there’s one other observation that I feel compelled to share before we move on. The vocals in this track are obviously doubled. Again, your average portable stereo Bluetooth speaker could confirm that. One little thing I’ve never noticed before in the hundreds of times I’ve dug deep into this track, though, is that the vocals in the left channel are more distorted than those in the right. Both have a decidedly low-fi vibe, but you can really hear that the left track was roughed up a bit more than the right. That adds a level of nuance to the mix that’s often lost.

Musical Fidelity

Am I saying the Musical Fidelity is the only amp I’ve ever auditioned that could illuminate this element of the mix? Of course not. I’m simply saying this is the first time I’ve noticed it, and I’m sort of obsessed with the White Stripes the way my six-year-old nephew is obsessed with Pokémon cards.

For something completely different, I turned my attention to “Come Around,” the second cut from Sarah Jarosz’s Follow Me Down (16/44.1 FLAC, Sugar Hill Records/Qobuz). This one can be tricksy, in that the fidelity of the recording is obviously much higher than anything the White Stripes ever recorded, but the mix is incredibly dense and occasionally chaotic. The bass, drums, guitars, fiddles, and banjo almost seem to be in conflict, rhythmically speaking. The only way to fully make sense of the instrumentation is if every instrument has its distinct place in the soundstage. Good transient response is essential. Without it, this song can lean toward cacophony in spots. Digging back through my mental Rolodex of recently auditioned integrated amps, the only one that stands out as handling this song as well as the Musical Fidelity was Marantz’s PM-KI Ruby, which sells for about $1200 more.

Musical Fidelity

Speaking of the KI-Ruby, I know I went on at length in the review of that piece about its handling of “Jimi Thing” from Dave Matthews Band’s Under the Table and Dreaming (24/44.1 FLAC, RCA Records/Qobuz). The width and depth of the soundstage. The little details like fret noise and string windings. The dynamics and authority of the bass. Mind you, auditory memory is incredibly short-term and highly unreliable, but if I didn’t think my SoundStage! overlords (or readers) would catch it, I could have just copied and pasted those paragraphs from the KI-Ruby review into this review and saved myself some time.

The M6si simply strikes the right balance of precision without sounding analytical, weight without sounding sloppy, and dynamics without sounding at all put out about it. And as long as you’re not relying on the USB input, it’s also an eerily silent amp.

Musical Fidelity

With my Oppo turned off, I cranked the volume knob to the ten o’clock position (right around where I set it when I want the music to tug at the skin on my face without outright peeling it off my skull) and put my ear right up to the tweeter of the left speaker. I couldn’t hear a thing. In fact, I didn’t even begin to hear some barely perceptible hiss until the knob struck high noon or thereabouts. At that level, if by chance music had started playing for whatever reason, my career as an audio journalist would have been over in an instant.

You can really hear the benefit of that in songs like “My Boy Lollipop (feat. Alana Davis)” from Ernest Ranglin’s Order of Distinction (16/44.1 FLAC, Milk River Music/Qobuz). The track begins with a playful “BOMP BOMP” from the bass and drums, followed by a two-beat rest before the band joins in. That rest isn’t entirely silent on the recording, of course. There’s the natural room decay, and then right before the music resumes, you can hear a very subtle click from what sounds like the drumsticks tapping one another. But in a brief slice of time, after the room settles down and before that very subtle clack, it’s as silent as possible. And the black background of the M6si really let me appreciate that. It gave the music that much more punch, that much more impact. It added more dimensionality to the mix. It let itty-bitty details shine through.

Musical Fidelity

One other general observation that isn’t specific to any one listening selection is that the M6si maintained its dynamic punch, its detail, its spaciousness, its precision, and its utter musicality even at very low listening levels. There’s something somewhat unintuitive about employing such a behemoth of an amp as a background-listening device, but it proved perfect for that. I found myself leaving it on at lower volumes while I was working because, even at unobtrusive listening levels, it still sounded fantastic.

How does the Musical Fidelity M6si stack up against more current competition?

I’ve already tipped my hand on this, but of the integrated amps I’ve reviewed in recent history, the one that best matches the M6si in terms of bass authority, dynamics, finesse, soundstaging, imaging, low noise, and low distortion is the Marantz PM-KI Ruby. That amp has been gone from my home for months, so A/Bing them wasn’t possible. As such, all I really have are my impressions of the PM-KI Ruby and my listening notes. But the two amps definitely had the same impact on me, sonically speaking.

That said, if my memory of the Marantz is accurate, I think the Musical Fidelity is ever-so-slightly more neutral but perhaps not quite as detailed. Close, but not quite. The M6si is definitely more powerful, though, and has niceties (which may be essentials for some) like preamp outputs. It also sells for $1209 less.

At or around this price, I also really love the Naim Uniti Atom ($3290). It’s a very different animal than the M6si, though. For one thing, its 40Wpc output means that you’ll need to be a little more selective about the speakers with which you pair it and the room in which you install it.

On the other hand, in addition to being an integrated amp and DAC, it’s also a nice media streamer in its own right. It’s a little limited in terms of analog inputs, with only one stereo RCA in. But it has two optical ins and a coaxial digital in, as well as Wi-Fi connectivity (including Apple AirPlay support) and a wired ethernet port. There’s even an HDMI ARC port. But most importantly, the thing simply sounds amazing—when paired with relatively easy-to-drive speakers, that is.

TL;DR: Should you buy the Musical Fidelity M6si integrated amp?

It depends on what you’re looking for in an int-amp, honestly. If you’re in the market for an all-analog* unit with a built-in phono stage, super-low noise, and more power than you could ever reasonably need in most rooms, it’s a hell of a good piece of kit. (*And yes, I know it technically has a USB DAC, but it’s a noisy Audio Class 1.0 device that doesn’t support sampling rates higher than 96kHz. So it’s probably useless to most SoundStage! readers.)

Musical Fidelity

In terms of its sonic prowess, the M6si holds its own against amps costing at least $1000 more. If I had to sum up its sonic performance in a word, I think I would go with “effortless.” Give me two words, and I would add “transparent” to the list. Its industrial design is simply scrumptious, and it’s as simple to configure and operate as you could ever hope for. True, the remote control is unfortunate. But aside from the outdated and noisy USB connection, there’s literally no other nit I can find to pick.

In terms of performance, this would be an incredible amp at $5000. The fact that it sells for less than $3000 is straight-up ridiculous.

. . . Dennis Burger

Note: for the full suite of measurements from the SoundStage! Audio-Electronics Lab, click this link.

Associated Equipment

  • Speakers: Sonus Faber Lumina V, Paradigm Studio 100 v.5
  • Speaker-level connections: ELAC Sensible speaker cables
  • Line-level connections: Straight Wire Encore II analog interconnects
  • Source: Oppo BDP-105 Blu-ray player
  • Power protection: SurgeX XR115 power conditioner

Musical Fidelity M6si Integrated Amplifier-DAC
Price: $2790.
Warranty: Two years parts and labor.

Musical Fidelity
A Division of Audio Tuning Vertriebs GmbH
Margaretenstrasse 98
A-1050 Wien
Phone: +43 1 544 858 0400


North American distributor:
Focal Naim North America
313 Rue Marion
Repentigny, QC J5Z 4W8
Phone: (800) 663-9352 (USA), (866) 271-5689 (Canada)