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FiiO M23

It’s not quite a single-handed effort, but there’s little doubt that FiiO is really the only meaningful obstacle standing between Astell & Kern and complete domination of the digital audio player market. The Chinese specialist has been turning out DAPs of lesser or greater excellence for quite a while now - and as well as delivering very gratifying performance, its machines have always been competitively priced.

For instance, at £649 this new M23 device is not one of FiiO’s most affordable - but it’s still a full fifty quid cheaper than Astell & Kern’s (admittedly excellent) entry-level A&norma SR25 mkII. And, on paper at least, it seems fully equipped to continue FiiO’s proud record of both offering cracking value to consumers and putting the frighteners on its competition.

Never mind ‘on paper’, though - what’s the FiiO M23 digital audio player like in practice?

Sound quality

As far as ‘sound quality’ goes, the FiiO M23 needs no excuses made for it. Everything it does, it does with the sort of instinctive correctness that makes every listen a pleasure, and every listening session longer than you had intended it to be.

No matter if it’s dealing with wired or wireless headphones, no matter if your content is CD-standard 16bit/44.1kHz or full-fat 24bit/192kHz FLAC files, the FiiO M23 is straightforwardly enjoyable to listen to. It does all the analytical, forensic stuff you want it to do, but it’s never uptight about it - instead, it’s a direct and musical performer.

Tonally, it’s really well judged - it’s natural and neutral, with no unwarranted heat and no unwelcome chilliness. Frequency response is nicely even from the top to the bottom of the range - no area is overstated and no area is underplayed. And the entire frequency range knits together smoothly, which helps no end when it comes to the impression of unity and togetherness the M23 can create.

There’s considerable punch and drive at the bottom of the frequency range, but it’s all properly controlled and never  impacts on momentum - and that means rhythmic expression is really good, too. At the top end there’s absolutely as much bite and shine as is acceptable - but the M23 never threatens to get out of hand where treble response is concerned. And in between, the FiiO communicates in torrents through the midrange - any vocalist, of any level of technique and any kind of emotional mind-state, is articulated with real positivity.

Detail levels are high across the board, and the soundstage the FiiO creates is plenty big enough for even the most complex recordings to be neatly laid out. Dynamic headroom is considerable, and the attention the M23 pays to harmonic variations is approaching the fanatical.  

All the above assumes you’ve left well alone when it comes to adjustment of the frequency curve - ‘flat’, where EQ settings are concerned, is the name of the game here. Oh, FiiO offers the end user quite a bit of input into the sound of the M23 - the on-screen menus allow you to adjust the EQ frequency point, bandwidth and gain in order to fine-tune the output. But for my money, you can only make the M23 sound ‘different’, rather than ‘better’, by imagining you know better than FiiO’s engineers…

Living with

In the most literal sense, ‘living with’ the FiiO M23 isn’t all that tricky - you simply have to be able to accommodate its 137x76x18mm (HxWxD) size and 299g weight. A sturdy pocket or bag is in order, then - but at least FiiO provides a protective case (silicone of the ‘blue titanium’ finish, leather for the ‘stainless steel’ alternative) to mitigate those pointy corners.

It’s pretty easy to live with the M23 where operability is concerned, too. It uses a modified version of Android 12 as an operating system, and a Qualcomm Snapdragon 660 processor to run the show - and the net result is a big (5.5in, 720x1440 resolution), bright touchscreen that’s about as responsive as these things ever get. And the physical controls arranged around the frame of the player (play/pause, skip forwards/backwards, volume up/down, a ‘hold’ button to prevent unintentional inputs, and a ‘multifunction’ button you can decide the use of) are positive in their actions too. The FiiO may have ‘only’ 64Gb of internal memory, but a) the operating system doesn’t eat into it too badly, and b) there’s a microSD slot on the bottom of the player that can accept cards of up to 2TB.

The base of the M23 features a couple of USB-C slots - one is for charging the 5500mAh battery, the other is for data transfer. And FiiO has gone to significant lengths to protect the battery here. As well as a dual-mode fast-charging system that allows for extreme fast-charging (up to 30W) if the battery level is very low, switching to a more common fast-charge once the battery approaches its fully charged state, there’s also ‘D-mode’ that’s activate by a physical switch on the side of the player. ‘D-mode’ means ‘desktop mode’ - and when it’s engaged the M23 is completely powered by an external source plugged into the appropriate USB-C input, bypassing the battery entirely. Which means the FiiO can be an item of desktop audio equipment with no impact on its battery whatsoever. Battery life, by the way, is an extremely handy 10 hours or so from a single charge.

As well as acting as a desktop DAC, the M23 can happily power wired or wireless headphones. The top of the chassis has 3.5mm and 4.4mm outputs, and its Bluetooth 5.0-powered connectivity works in both directions with SBC, AAC, aptX HD and LDAC codec compatibility. The 3.5mm socket is hybrid, in fact, and can act as a digital coaxial output of you want to bypass the FiiO’s DAC architecture.

You should give the M23 a long, hard listen before you decide that’s the way to go, though. FiiO has kitted the M23 out with a pair of AKM digital-to-analogue conversion chipsets: the AK4191EQ and AK4499EX. Operating in tandem, they keep the digital and analogue stages entirely separate and utilise ‘DWA routing’ technology to keep the signal-to-noise ratio to an absolute minimum. And they allow the M23 to deal with digital audio files of almost every type (MQA included) up to a resolution of 24bit/384kHz and DSD256.

The output of this relatively complex DAC arrangement is amplified by FiiO’s latest refinement of THX amplification. The company has taken the THX AAA 78 architecture it used in its M11 model and its variants, and fettled it to the point it’s now called THX AAA 78+ - the design is intended to offer greater power output, greater precision and minimal distortion.

And, of course, there’s plenty more besides. FiiO is pleased with its four-stage, 20-rail power supply (designed to provide consistent power to both the analogue and digital sections of the audio circuit and to easily handle big fluctuations in demand), as it is with the 28 high-capacity polymer tantalum capacitors that contribute towards the same power-supply goals. It’s proud of the Digital Audio Purification System (‘DAPS’) that avoids resampling while maintaining the original sampling rate of the audio stream - no matter if the information is accessed via third-party apps, the FiiO Music app or when the M23 is in USB-DAC mode.

All of the above engineering rigorousness allows the FiiO to operate in five, soon to be six, listening modes: Android, Apple AirPlay, Bluetooth, ‘Pure Music’ and UPnP can all be used to access content. FiiO is in the process of securing certification that will allow the M23 to be Roon Ready, too.

So it would seem that ’living with’ the FiiO M23 is no kind of hardship at all. But it occasionally exhibits some mild operational instability of the sort I imagined had gone the way of CRT televisions and centre-right politicians. It’s not above pausing playback for no apparent reason, and it can very infrequently begin playback of a song from very slightly further in than the 0:00 start-point. It doesn’t sound like much, does it? That’s because it isn’t. But it’s disconcerting nonetheless, and the fact that it happens so rarely almost makes it a greater irritation - because it seems apparent that it doesn’t have to.  


If you take portable listening seriously, then you know a smartphone just doesn’t cut it - and the more capable your headphones, the more obvious that becomes. This isn’t the first time FiiO has made the case for a dedicated digital audio player, but the M23 might just be its best pound-for-pound offering so far. You’ll have to grit your teeth when it decides (as it apparently will, every now and then) to pause your playback, though…

Listening notes

Joan as Police Woman Anyone
The immediacy of the vocal line, the depth and texture of the bass sounds, the beautifully judged level of the harmony vocal, the sepia tones of the brass section… this is an endlessly gratifying recording, and the M23 lets you hear it to its fullest advantage.

Tortoise Ten-Day Interval
One of the less smart-arsed recordings in the Tortoise canon, this is a great test of transient response, speed and manoeuvrability. And by the band’s usual standards, it’s actually quite catchy - hummable, almost.

Wham! Everything She Wants

Heard as a huge DSD64 file, it’s impossible for the excesses of these 80s production values to overshadow just what a technician, and just what a potent communicator George Michael was. Midrange resolution is the key here, and the FiiO is very, very good at it.

What the press say

Why you should buy it

You buy the FiiO M23 because you have a) very good headphones, b) a top-tier streaming service subscription, c) some fully high-resolution content to load onto its internal memory, d) robust pockets and e) slightly more patience than you might be expecting to require.

Video review

Pair it with

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