Musical Fidelity M6si integrated amp review

m6i-silver-half-angled-frontYou will probably already be aware of what I think about Musical Fidelity, the thirty-odd year old top-end Hi-Fi firm. You may even have seen the unboxing of the beast. Now, after some quality hours spent with the Musical Fidelity M6si integrated amplifier, it’s time for my thoughts.

Let’s go through what the M6si has to offer first.

Those of you in the know will have already put two-and-two together and realised that the new M6si integrated amplifier replaces and, hopefully, improves on the outgoing M6i model. Not only has MF added more inputs but they’ve given the internals a thorough going over in order to improve the unit’s performance.


The M6si uses Musical Fidelity’s exclusive Surface Mount Design layout techniques. This reduces the size of the circuit board’s footprint which, in turn, reduces noise and greatly increases the options for internal layout.

What intrigued me and drew me to asking if I could test this amp is that the M6si is configured as a preamp with two completely separate and independent monoblock power amps which all just so happen to be sharing the same case. I know, right? More about that later.

The M6si is available with a black or silver front with the sides handed over to banks of cooling fins.

MF M6si unboxing 7 booty shotAround the back you have 4 line level RCA/phone inputs, 1 line level XLR balanced input, a dedicated phono input, and a USB B input which will play nice with 24 bit 96kHz audio streams.

Musical Fidelity has equipped the M6si with an analogue preamp output so you can hook up an external power amplifier or powered monitors.

On the front panel you get an individual button for each input source and an on/standby button. The huge volume dial rotates smoothly and I am such a fan of MF’s blue LEDs. Naturally, the M6si comes with a no-nonsense remote so you don’t have to risk leaving fingerprints on the amp. Your other choice is to wear the white cotton gloves that comes in the amp’s welcome pack.

So, is the M6si the sonic heavyweight that Musical Fidelity is hoping? Well, it’s definitely heavy as it tips the scales at 16.6 kg (21.3 kg when packed in the box I carried from the office).

Ears on

When you start getting in to the M6si’s price bracket you rightly should expect good things. Heck, I dig the sound of the V90 rig and all of it, including the Rega phono stage, wouldn’t cover the price of the amp. We might get close to the asking price if I throw in my Oppo disc player and PM-1 headphones too. Maybe.

So, I could just end the review here and say that the M6si does everything it should immaculately – but you expect more from me in regards to this bit of high fidelity kit, and rightly so.

That preamp with dual monoblock power amp configuration means that both channels perform virtually identically, not what you would expect from a ‘normal’ integrated amplifier.

Distortion is very low at less than 0.005%. More tellingly, high frequency distortion is incredibly low – at 10 kHz about 0.006% and at 20 kHz an astonishing 0.007%.

Channel separation is remarkable, as well as it being remarkably consistent. Most amplifiers (integrated or pre/power) tend to have worsening crosstalk with increasing frequency. Not so with the M6si.

mf m6si front gadgetynewsCD’s are lively and the amp starts to show it’s character once the dial goes beyond the 9 o’clock position. I had to keep in mind that this is rated with an output of 220 Watts per channel into 8 Ohms and I live in a small maisonette.

The 24-bit/96kHz asynchronous USB input uses exactly the same circuitry and technology as the highly regarded V-Links and other top quality computer interfaces. Jitter is all but eliminated and noise is incredibly low whilst distortion is virtually non-existent.

The M6si’s USB input is capable of dredging the finest details from your “invisible music” (as a friend described MP3, et al) source.

I spent a few days just listening to digital sources, whether CD, Hi-Fi Pure Audio, FLAC, or MP3 and the crispness and detail in playback was extremely impressive.

Through the V90 some tunes, such as the offerings from supergroup KXM, where the bass becomes very prominent in the recording the lows can on occasions be overbearing – not so through the M6si. The big amp seems to deal with everything on a much wider scale which results in more parity across the soundstage.

Jeff Buckley’s album Grace is just sublime and trickles through every inch of my living room through this amp. Nuances such as breaths between phrases and the sound of fingers muting strings suddenly become ‘real’ and in the room.

When I decided it was time to spin some black plastic on my Pro-ject Xpression through the M6si’s phono stage, that’s when things got interesting. The phono stage is switchable between MM and MC, just in case you were wondering.

I am good lad and had read that the new amp is equipped with a very accurate RIAA, within ± 0.5dB from 20 Hz to 20 kHz. I was also aware that it maintains its accuracy right up to 50 kHz.

That might mean a great deal to some of you and you should probably be suitably impressed.

mf m6si angle gadgetynewsAll I can say is that playing the heavy vinyl anniversary reissue of Dark Side of The Moon almost had me in tears. This took me right back to when listening to music was an all encompassing and emotional occasion, nay; experience. This is where the sound quality of this amp really stepped up to it’s asking price for me. I proceeded to test it with a variety of vinyl cuts from Prog to ‘The Pistols’ and the M6si just continued to ooze quality.

I returned to CDs as I felt that the amp had found its stride after a few hours and the M6si just remained effortless and unstressed even when I dared crank it up a bit. I can safely state that in any ‘normal’ room this amp will drive any loudspeaker easily and stably.

My personal listening party continued through some choice tracks from Jaco Pastorius, Charles Mingus, Stanley Clarke, Marvin Gaye, through to Tool, Heaven 17, Kate Bush, Gladys Knight, Talking Heads and so on.

I was not only enjoying this experience but also trying to find a weakness. But all I kept on discovering was an unstressed, clear, ungrainy sound quality.

Low frequencies were consistently delivered with an impressive attack but without any boominess. For example, the piano and upright bass interplay at the beginning (and throughout most of the piece) of Tuesday Wonderland by the Esbjorn Svennsson Trio is so warm and open it just wrapped me up in a luxurious dark wood blanket – that’s the only way I can describe it, and it’s meant to be positive.

Whilst on the subject of piano, the high notes still retain weight as well as clarity, whilst the mids sparkled. The decay of the notes just serves to pull you in to listen more intently.


The Musical Fidelity M6si truly boasts high-end sonic superiority but, at around £2,500, that would tend to be expected.

Price aside I can say that, thanks to its effortless level of power, even the most demanding of speakers are certain to be brought to life without any stress or issue from this remarkably capable amp.

The inspired pre/power amplification configuration found within this hefty unit allows it to produce a vast and immersive stereo image without it even remotely breaking its stride at any point.

The sound is clear, ungrainy and a genuine pleasure to experience. The high end is sweet and crystal clear, the midrange is punchy and dynamic, while the bass response is open and liquid.

If there is an amp this good, at this price, then I want to hear it. Until then, if you’re in the market for a new integrated amp with a really sweet phono stage, and have two-and-a-half-grand to spend on one, you really ought to check out the M6si.

Musical Fidelity M6si spec at a glance:
 Power output: 220 Watts per channel into 8 Ohms
 THD (+ noise): 107dB 'A' - weighted
 Frequency Response: +0, –0.1dB, 10Hz to 20 kHz
 4x Line Level RCA / Phono
 1x Line Level XLR Balanced
 USB input - type “B” socket up to and inc. 24 bit 96kHz USB audio stream
 Phono Input
 Sensitivity: 3mV nominal (MM), 0.4mV nominal (MC)
 Signal / noise ratio: >84dB ‘A’-weighted
 Input impedance: 47k Ohms (MM and MC)
 Frequency response: RIAA/IEC ±0.5dB 20Hz-20kHz
 Dimensions - WxHxD (mm): 440 x 125 x 400
 Weight (unpacked / packed): 16.6 kg/ 21.3 kg