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Moonriver Audio Model 404 Integrated Amplifier


I’ve heard a few older systems over the past couple of years. I’m talking about 20 to 30 years old. Inevitably vinyl based, you might assume that the electronics were pre-historic in hi-fi terms but I was more than surprised at how good they were. A recently serviced 30 year old Naim NAP250 with NAC 72 preamplifier and a HiCap power supply really shocked me. Its owner had upgraded to a modern pair of Focal speakers after the bass drivers in the original Linn speakers began to disintegrate. Even with the original Naim speaker cable, never the most refined, the up-front energy, speed and intensity of the sound certainly left me wondering how far we have come in amplifier innovation.

These experiences certainly made me think though. Bandwidth, power, speed and any number of distortion measurement might have improved but these yardsticks are difficult to use as anything other than an academic argument when the music sounds so good. And of course, the qualities that made good, musical amplifiers 30 years ago are actually the same I listen for now.

Then, before Christmas, with the world now in a different place, the Moonriver Model 404 amplifier arrived and after very little listening I realised that here was an amplifier that plugs straight into those same values in the way it opens an engaging window onto your music. A completely new name for me, Moonriver has an interesting back story. It is designed by Mr George Polychronidis in Malmö, Sweden where he and a small band of dedicated individuals really do hand-build each and every amplifier. There are two models currently in the range. The Model 404, under consideration here is the standard version while there is also a Model 404 Reference amplifier built around the same platform but with improvements through the design yet still bearing the same musical DNA. And, if you are wondering whether the name of the company has anything to do with the old romantic ballad of the same name, then the answer is apparently yes.


The 404 concept began about four years ago. George had designed and worked on many different types of audio electronics and through this grounding he acquired experience and knowledge before a clear concept for an integrated audio amplifier took shape. As he eloquently states, he was “Drowned in sound” and analysed in detail, every recording that “Spoke” to him. He cites the cost/performance balance that building an amplifier in Europe bring and just how much pure research he put into every section of the design to perfect all aspects of its construction and sound.

The look of the 404 is, to me, somewhat retro with a notable absence of anything other than the essentials. There is nothing superfluous in its design and if you are into recording, or adding processors, that tape monitor facility would be very useful despite its rarity. A fine aspect of its design is the ability to add reasonably priced internal modules to expand its usefulness. These can be installed from new or retrofitted – ideally by the dealer – and the internal design makes this easy to achieve at home. There is a straight MM phono stage or one that incorporates a MC as well. A glance at the back panel shows a USB input. This requires another module in the shape of a (forthcoming) asynchronous DAC to be fitted, expanding the amplifier’s possibilities enormously I think this architecture is excellent because, if you want a straightforward line-stage integrated then you won’t need to incur the added costs of extra internals but if you use a turntable or want the amplifier to act as a DAC, that’s an easy fix too. It also has remote control with a decent, though not exceptional receiving window.

I really like the way George has learned from his restoring and repairing days and made the 404 so accessible to service too, with a removable top and bottom that give excellent access to the main circuit board which utilises through-the-hole components for extra reliability. That’s good design work. He followed a traditional high-end philosophy with ultra short signal paths and minimal components all built around the power supply that has separate windings for each section. The ALPS volume control is an established and respected product while the inclusion of a parallel balance control might be thought of as an unnecessary complication by some, George insists that, sonically, it is entirely non-intrusive, and as such is not defeatable. This control and the inclusion of a mono/stereo switch and especially the tape monitor rotary knob are perhaps a little unusual these days but make sense and they were deemed essential by the designer. Personally, I sit square on to my system so the balance control will get no use from me but I completely understand its inclusion as many systems, particularly where space is at a premium are somewhat asymmetrical in layout and the option to change the balance by a few dB would be welcome.

While installing the Moonriver 404 you notice that everything you touch feels good. The RCA inputs and the excellent speaker outputs, the volume control and front panel switching and when powered up this is a very quiet amplifier indeed. No clicks or pops and a blackness against which it projects its 50 watt per channel musical muscle. It is perhaps surprising but most reviewers will tell you that audio components each have an individual ‘feel’ when you install them. Some just give more confidence than others. The 404 does just that.


I slotted it straight into my system between the dCS Vivaldi transport and DAC and the Bridge streamer and the Wilson Duette 2 loudspeakers. The Vivaldi will push the amplifier’s resolution to the limit and the Wilsons, though not particularly difficult to drive from a load point of view, don’t take any prisoners in resolving everything that the amplifier asks of them. I think it’s fair to say that Moonriver would need to punch above its weight to be a real contender in this company and that, given the choice, a far, far more expensive design would be the usual choice in this system.

I’ll start by saying that the 404 loves input level. The Vivaldi will output into line stages at either 2 or 6V. I think it always sounds livelier and more dynamic at full level (6V) but that some amplifiers sound slightly out of breath with the output level control at 100dB and need a small touch of trimming to feel entirely comfortable. The 404, as I said, loves level. Flat out on the 6V setting and it just flew out of the traps with a confident musical message that just grew and grew. Even from cold it took very little time to get into its stride and after an hour or so I stopped thinking that it could ever sound out of its depth. It was shockingly good but also incredibly charming in its musical style. Tonally, its balance is about perfect and the Wilson speakers gave it scale and weight too. I hadn’t listened to very much music before I was searching for any real criticism I could make. It felt very much at home. So, I took my reviewers hat off and for the next month in lockdown, I just listened to it for hours on end without a single issue.

Great systems are able to change flavour to suit the music. They really need to have this chameleon-like character where they can channel their attributes and this system had that in abundance. It is both fast and slow as the need arises but the one thing that shines out is the feeling of musical textures that it brings into the room plus the way it allows the music to unfold time-wise without ever sounding rushed or stressed. I’d point to Mandolin Orange, a two-piece act with deep roots in bluegrass, gospel and even a hint of pop melody too. Sparse instrumentation contrast the naked vocals and lead you along the threads and tunes of the very traditional but there’s generally a surprise departure or two along the way. It’s the atmosphere and the contrasts though that give the music its charm and rhythmic ease plus the fact that they are both superb musicians. The Moonriver is totally at home here. Its quietness and lack of compression give the duo time and space to stroll through cowboy melodies interspersed with fiddle and mandolin interludes that support their lovely vocal harmonies.

Did I mention texture? The MQA stream of Melody Gardot’s Sunset In The Blue was stunning. I would say that no modern female singer manages this style of music like Gardot. This album is produced by Larry Klein who must be the best when it comes to understanding how to showcase a female artist’s talent. This is a very sensuous and totally intimate recording where Klein supports Melody with a familiar backdrop of delicious string arrangements that manage to sound both old and new at the same time. It is a magnificent recording, shrouded in mystery and restraint, question and answer, yet with an expansive velvety texture that you can practically touch as it fills the room with sheer tonal breadth. This album was made for the Moonriver. With its breathy presence and delicious tempos floating around Melody’s close-miked vocals it paints a giant picture of an artist so enormously capable and completely at home with the glorious orchestral scoring. Klein shows that he is a master of time here as he lets her slip from English to Portuguese, shaping her vocals with a lift here and a breath there that give her a sense of musicality and command that is more than rare among today’s singers. The way that the 404 reveals the musical embellishments, especially in the low mix, is really impressive as is the depth and articulation of the whole soundstage. It has a way with strings that often draws people to tube amplifiers. The warmth and smooth envelope of the notes and the lack of astringency are really notable. Then there is that black and very still background again. When she sings ‘Moon River’ it felt as if a circle had been completed.

Excellent though it is on such sultry and atmospheric music it would be a mistake to think that it can’t push when required. In fact it can kick it much harder than it might have seduced you into believing, but it does it with great control and steadfastly refuses to grow confused or breathless as the transient levels rise and the tempos increase. The one thing it is not is bright. There’s a leaning toward amplifiers with a hard tonal edge these days but the 404 avoids this in favour of its own voice.


So, you’re wondering at this stage if there are any downsides or weaker aspects? I would say that, at the price, the amplifier does everything you could reasonably expect. It could perhaps be a little more airy and transparent at high frequencies and perhaps the bass might have a touch more weight and tautness. But I would assume that the reference version with its improved power supply would address these areas. But this is an amplifier with impeccable balance and poise. Criticism seems harsh as it is such a well rounded design. I have certainly heard amplifiers costing far more that are not significantly better and every design has its limitations. But, considering the very attractive price and the performance offered it just has to be a recommendation from me.


  • Type: Single box integrated amplifier
  • Power Output: 50 watts per channel into 8 ohms
  • Inputs: 5 (line 1 and 4 optionally occupied by phono stage and USB DAC respectively, 1 x tape loop)
  • Outputs: 2× Pre Out, 1 × Rec Out (RCA)
  • Freq. Response: 10Hz–50 kHz
  • MM phono stage gain: 40dB
  • MC phono stage gain: 50dB
  • MM Input impedance: 47k
  • MC Input impedance: 100 ohms
  • Signal to noise ratio: 85dB (line)
  • Remote: Yes
  • Dimensions: 135 × 430 × 390mm (H×W×D)
  • Weight: 12kg
  • Price: £3,095
  • MM Phono module: £375
  • MM/MC Phono module: £525


URL: moonriveraudio.com

UK Distributor: Whole Note Distribution

URL: wholenotedistribution.co.uk


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