Musical Fidelity M6si Test

Musical Fidelity has been developing and producing high-quality Hi-Fi equipment for over 30 years. The release of each new device to the market is always preceded by a lot of painstaking work by designers and engineers.

We gladly agreed to test the new M6si integrated power amplifier. This device is an improved and modified version of the M6i amplifier. The new product features higher output power, an increased number of inputs, and an expanded dynamic range.

Design Features of Musical Fidelity M6si

In the M6si, the developers used Surface Mount technology for elements on a printed circuit board. It made it possible to greatly reduce the length of printed conductors and thereby reduce the level of interference induced on them. The printed circuit boards themselves have become much more compact, which gave designers more freedom to place them in the case. Another interesting solution is the use of separate monoblock power amplifiers for the left and right channels with separate power supply and a common monoblock preamplifier. But we will return to this later.

The amplifier is available in two colors: black and silver. On the sides of the case, there are massive finned radiators. One look at them is enough to understand that this is a real “powerful beast”. And this is completely true, given the power output of the device. The Musical Fidelity M6si patch panel houses four analog stereo RCA pairs, one balanced XLR port, and a dedicated input for connecting an MM/MC pickup. Plus, there is an asynchronous USB terminal compatible with 24-bit / 96 kHz digital audio stream. Additionally, the M6si is equipped with a line output for connecting an external power amplifier or high-quality active monitors.

On the front panel of the amplifier, there are separate buttons for activating each input port with LED indicators. The volume control located in the center of the front panel has a classic design with a massive round knob. The Musical Fidelity M6si comes with a rather austere remote control, so you’re unlikely to leave your fingerprints on the amp’s control panel. However, the developers carefully included a pair of gloves in the packaging. Speaking about the weight of the amplifier, we cannot call it super heavy, although, of course, 16.6 kg is quite a respectable weight.

Musical Fidelity M6si Listening

When we start listening to Hi-Fi equipment, we can always expect excellent sound. But you always want to get something more than just high-quality sound. In order to fully reveal all the capabilities of the new product, we tried to find “worthy partners” for it from the same category. As a signal source, we chose a V90 audio DAC, a Rega turntable with a phono preamplifier, as well as an Oppo CD player and Oppo PM-1 headphones.

Recalling the internal structure of the Musical Fidelity M6si, we note once again that it is made according to a three-block circuit, which is not typical for conventional “integrated devices”. The amplifier’s THD is incredibly low, less than 0.005%. At a frequency of 10 kHz it becomes slightly higher – 0.006%, and even at a frequency of 20 kHz it does not exceed 0.007%. This result can be considered a kind of record for integrated amplifiers. Channel separation is almost perfect, and most importantly, does not depend on power. Most amps always experience higher levels of crosstalk as volume increases, but not the Musical Fidelity M6si.

The amplifier begins to reveal its capabilities immediately. After a while, our hall was immediately completely filled with magnificent music. The sound field was dense and voluminous, and there was still a solid margin of power. It should be noted here that the test was carried out at home in a two-level apartment, and of course, the possibilities of the Musical Fidelity M6si were more than enough for its high-quality voice acting.

The second pleasant surprise was the impeccable sound of our digital compositions through the built-in USB port. Jitter and digital noise levels were extremely low, and we certainly didn’t hear any distortion. On the contrary, the sound of well-known MP3 files has become more detailed and voluminous. It seemed that Musical Fidelity M6si managed in some completely incomprehensible way to open layers previously hidden from our ears in these compositions. And now we are already hearing a completely new, truly “live” sound, enriched with energy and new details.

During the test, we listened to the amplifier for several days with various digital sources: CD players, Hi-Fi Pure Audio, FLAC, and MP3 files. In all cases, the sound of the amplifier was extremely clear and dynamic with incredible detail and volume. Using the V90, we listened to hits from supergroup KXM. The soundtrack sounded great. The high power of the Musical Fidelity M6si enriched the bass lines, adding palpable depth and energy to them. The nature of the created sound stage began to be perceived as more ambitious. Jeff Buckley’s musical tracks from the Grace album seemed to smoothly “flow” from the acoustic systems into the hall, gradually filling every centimeter of the room. And superbly distinguishable sound nuances, such as breaths between phrases or touching strings with fingers, created the full effect of the presence of the performer in the room.

Inspired by the results, we decided that it was time for the real “king of music” – vinyl. Having read that the Musical Fidelity M6si has a built-in RIAA-rated phono stage with ±0.5 dB accuracy from 20 Hz to 20 kHz, we decided to use it for the test. Moreover, the manufacturer claims correct operation of the phono stage up to 50 kHz. Agree, Such opportunities are impressive, and it’s a sin not to take advantage of this! Note that if necessary, you can select the type of cartridge MM or MC. We decided to start with the anniversary vinyl edition of Dark Side of The Moon. Without undue modesty, we can say that the sound of this disc simply captivated us. Literally, tears came to our eyes, we heard such an accurate and emotion-filled sound. Believe me, this sound is worth a lot!

We then went back to listening to the CD, turning up the volume on our system slightly. Of course, in this case, the amplifier pleased us with excellent sound, although it is worth noting that this volume level for our room was already maximum. It seemed that if we turned the knob a little more, the glass in our windows would begin to vibrate. Without a doubt, we can say that the Musical Fidelity M6si can easily cope with the “drive” of even the most complex acoustics. We listened to random tracks from the following artists: Jaco Pastorius, Charles Mingus, Stanley Clarke, Marvin Gaye, and many others. We honestly tried to find a “weak spot” in the device. But with each new track, we discovered new capabilities of the device more and more. Low frequencies pleased the ear with amazing energy, the realism of sound, and high-quality attack; we did not hear any booming or “mumbling”.

The upper frequencies of the audio spectrum were clear and pure with characteristic transparency. And the mid frequencies are perfectly articulated and developed.


The Musical Fidelity M6si really gave us some real high-end sound. Thanks to its high output power and increased damping coefficient, it is able to “breathe energy” into any speaker system, even the most difficult to drive. This “beast” copes well with any musical composition, even the most dynamic, and most importantly does not miss a single musical nuance. Its crystal clear sound with open and energetic bass, clear and dynamic mids, and transparent highs is capable of delighting the ears of any audiophile. It’s safe to say that the Musical Fidelity M6si is currently the best-integrated amplifier we’ve heard.

Musical Fidelity M6si Specifications

Type – Amplifier

Output power – 220 W per channel into 8 Ohm load

Total Harmonic Distortion – <0.007% (typical value measured over 20Hz – 20kHz frequency band)

Signal-to-noise ratio – > 107 dB (weighted average)

Frequently reproduced range – from 10 Hz to 20 kHz (with uneven frequency response +0 – -0.1 dB)

Input ports

4 analog stereo pairs Line Level RCA / Phono

1 balanced XLR port (Line level)

Asynchronous USB port, type “B” socket (supports 24-bit audio stream with 96 kHz sampling rate)

Phono input

Sensitivity – 3mV nominal (when connecting an MM cartridge), 0.4mV nominal (when connecting an MC cartridge)

Signal-to-noise ratio – > 84 dB

Input impedance – 47 kOhm (for MM and MC cartridges)

Frequency Response RIAA/IEC – ±0.5dB 20Hz-20kHz

Weight and dimensions

Size (WxHxD) – 440 x 125 x 400 mm

Weight (unpacked/packed) – 16.6 kg / 21.3 kg

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