FiiO M15S Review


Sound performance

For the purpose of this review, I used the Beyerdynamic DT900 Pro X, the FiiO FD7, the Hifiman Svanar and the all new FiiO FF5. All files were streamed from Spotify – for convenience – and Apple Music – in Hi-Res when available – and my own catalog through local storage.

Overall signature

So, is the FiiO M15S a worthy successor to the original M15? Yes, but don’t ditch your old M15 just yet.

Sure, this new player offers a real performance upgrade compared to its predecessor – better dynamic range, punchier lows and even more power – but at the same time, it misses the organic feeling of the first model. More precisely, this new model sounds more like a shoehorned M17, than a M15+.

It’s everything I like about FiiO with gorgeous lows, vibrant voices, clear highs, and just that little zest of fun. It’s a lot more accurate than the M15, sometimes a bit too much to be quite honest, and dynamic range is just insane with big cans like the Sennheiser HD800S. And yes, like the M17, you’d be able to drive massive headphones like the old Senn, or the Hifiman Svanar – which isn’t specially hard to drive, but comes with a super low sensitivity.


Audeze LCD-X, Sennheiser HD800S, Meze Empyrean, even my old HiFiman HE-6, none gave the FiiO any difficulty, even more when I plugged them in 4.4mm/2.5mm. In fact, I don’t know who will ever use – or need – the ultra mode: switching to this special setting might even obliter your eardrums.

But, this powers really comes handy on many occasion. Lows are gorgeous, with just the right amount of “oomph” and not only does the soundstage feel wider, compared to the OG M15, it also feels more natural with on-point positioning of each and every instruments. A good example was *Dark Moon from Okonski,* where the drum rolls happening at 1:20 appeared almost life-like to my ears.

Sure, I miss the THX-AAA amps stiffness, specifically on electro tracks like Athena from Hi-Lo but, compared to the M15, the M15S took the upped hand every time. It’s not the same organic signature that I was accustomed to, and paired with the FiiO FD7/FD5, it misses that little spark only found on high-end AKM chips, but other than that, I still think that FiiO offers the best bass from any player in this price range, even if newcomers like Tempotec aren’t too far.


Head to head against the Tempotec Variations V6 there were a few similarities – both share an ESS core – but 9 out of 10 the M15S took the upper hand, with a wider soundstage, sharper mids, deeper highs, and bigger headroom, and so without the THX-AAA op-amp.

And, where the M15S really shined, was with planar headphones. As I wrote before, all of my big cans were driven with ears, he sheer power, combined with ESS accuracy delivering the rich experience you’d expect from a $1000 DAP & headphone combo. There is always something magical in getting that level of sound pressure, with “portable” setup, when you recall that just a few years ago, you’d need to pair a portable amp to get that same definition.

On that regard, if FiiO offers four levels of gain (low/mid/high/circum) to fit every type of headset/IEMs I mostly switched between low and high, the low-level proving to be sufficient with almost all of my IEMs, and the high one already powerful enough to drive the HD800S. Sure, I couldn’t reach the same level of resolution, found on the FiiO M17, but considering the price, and more importantly the size, that’s not a real flaw in my opinion.

Don’t get me wrong, sound-wise, if not as impressive as the M17 this new M15S remains a few steps above the M11 Plus, and the M15, thanks to its large power reserve: deep bass, smooth mids, excellent layering, it’s an amazing portable source in and out – a real upgrade from the M11S and M11 Plus, sonically speaking.


But, if you really want to get to the upper-level, I’ve got an advice for you: pair that with the Astell&Kern PA10, in 4.4mm Pentaconn. I did it, out of curiosity first, then for real testing purposes: it’s wondrous. Not only does the PA10 ensures a linear sound signature but that combo also brings forth a wider soundstage, that feels even more immersive.

Okay, that push the player into FiiO’s M17 territory, but if you take some distance, the combo looks almost as big, weight almost as much, and sounds… almost as good..

All in all, a great experience once again, but you expected no less, didn’t you?



Highs: clean and straight. If ESS is sometimes labelled as boring due to its linear tonal balance, I’m a big fan of their signature, even more, when FiiO’s the one using their chip Even at low volume, the player was able to output a lot of information, and whether if it was in low/mid/high gain, the FiiO M15S gave me acute highs, with no hiss whatsoever.

Track : Poly – Thylacine

Mids: excellent layering and dynamic. Voices have always been good on FiiO players, and the M15S is no exception. This is especially true with big cans and thanks to its large power reserve, the DAP delivers superb vocals, almost effortlessly, whether paired with my LCD-X, or smaller cans like the DT900 Pro X.

Track : Wanderer – Mogli

Lows: even better than before. The THX-AAA amps might be gone, but FiiO’s spirit remained the same, the player being capable to reach the deepest/lowest note, with ease. You never have to raise the volume, but if you do the bass will remain strong and steady, with no dragging sound nor latency – the BEST bass you can get in this price range.

Tracks : Way down we go – Kaleo


Noise and power

Noise: if the previous models were already silent, this model is now a step above and the M11S outputs a superb background, just a tad under the Variations V6, the new top-dog in this regard.

My hypersensitive Onkyo could not spot anything, even with Bluetooth and Wi-Fi turned on. EMI shielding made a great job and I never encountered any parasite or buzz during my listening.

Power: once again, FiiO offers four different levels of gain for its player. If low is really low and should only be used with IEMs, the mid-level was enough for 90% of my headphones, even with the BeyerDynamic. Obviously, if you want to drive cans like the Audeze or Sennheiser flagship, you better put the gain in high and stick to the balanced output.

Line out/Coax out: If the FiiO M11S kept the classic 3.5mm output, to connect your amp, the player also introduces a new balanced, 4.4mm, line-out – the one I used with the A&K PA10.



Once again, FiiO did what they do best: take a good player and enhance every part of it, to re-establish their leadership position.

If not cheap, the FiiO M15S is now $300 less expensive than the first M15, and $700 more affordable than the M17 – which shares a lot of common trait with this new player. It won’t be as popular as the FiiO M11S, but by offering 70% of the M17 performance and versatility, for just $1000, this new DAP will definitely appeal to audiophiles like me that wants high-end performances, but don’t want to pay the TOTL toll.

All in all, the FiiO M15S is a remarkable player that manages to build upon the already impressive foundation laid by the M15. UI is fast, the sound is amazing, and the only real flaw will be the average battery life, that will force you to charge your player quite often. So if you’ve been holding to your “old” M15, and were considering the M17 too expensive, and the M11 Plus not potent enough, the new M15S finally is the replacement you waited for.

A must-have once more! The M15S is now featured on our Best DAP list, where are all recommended DAPs are listed.

Pros :

– excellent sound quality
– great build quality and lovely UI
– all the inputs/outputs you’ll ever need
– can scale with headphone amps quite easily
– nice bundle with a great case


– big and not the easiest to carry around
– battery life is not the best


Page 1: about FiiO

Page 2: UI, Usage, Bundle

Page 3: Technical specifications

Page 4: Sound performance

4.6/5 - (34 votes)

A nerdy guy with a passion for audio and gadgets, he likes to combine his DAC and his swiss knife. Even after more than 10 years of experience, Nanotechnos still collects all gear he gets, even his first MPMAN MP3 player. He likes spreadsheets, technical specs and all this amazing(ly boring) numbers. But most of all, he loves music: electro, classical, dubstep, Debussy : the daily playlist.


  • Reply April 29, 2023

    William Aitchison

    Hi….many thanks for this superb review, I have a FiiO M15S (previous was an M11 ESS) and this M15S is MUCH better and I agree with every word of the review….I waited ages for this Mark II M15 and I am not disappointed….
    Interestingly I also have the A & K PA10 and agree with the reviewer, it lifts the audio quality to another level…..a word of caution though, I found using the A &K supplied unbalanced jumper cable not that good but going to a 4.4mm to 4.4mm balanced connector ( as shown in the review) made a substantial difference the the sound quality and I’m surprised A & K did not include one considering the cost ay the PA10 and the very modest cost of the jumper cable.
    That said, the FiiO M15S is the best FiiO I’ve had yet (and I’ve had a few!) and once again thank you for a great review.
    Happy listening!!

  • Reply May 1, 2023

    Gregory David

    Thanks for the review! Question, I would like to use the M15s as a transport from 3.5 mm to COAX, not the USB. Did you try out this function?



  • Reply May 16, 2023


    what is up with all these black and white photos? You really cant get a good feel or look at the player doing that.

  • Reply June 12, 2023


    Would love to hear thoughts on how it compares to the ibasso dx240.

  • Reply December 10, 2023


    This is a fair review but it misses the main feature (except for a dismissive passing reference). This is the provision of additional gain levels when the DAP is plugged into a fast charger. The super and ultra high levels for over-the-ear cans make a transformative difference in precision, clarity, tonality and staging. You don’t have to listen with a high volume setting to get the benefit. I had been getting a bit disappointed with the M15S and Hifiman Arya combination until I “discovered” this hidden feature, after deciding to by a fast charger (£10). It unlocked the qualities of both. Of course, this is not a portable mode, but it is outstandingly good. You don’t get any of it without the mains electricity. Hence this tepid review.

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