Fiio M15S

The M15S by FiiO promises to be the middle-ground DAP for portable and stationary use. Is extra power and some cool features enough to secure it a place on the market? Let’s see how much we can extract from the newest DAP in FiiO's portfolio coming at $999.

Introduction to the FiiO M15S review

I had the FiiO M11 Plus ESS (which I reviewed) some time ago and I loved it. Then, I wanted to try something else and swapped it for the Chord Mojo 2. Worst decision ever, to be honest. Got rid of it quicker, than you can say “but why, it’s supposedly so good?”. Not for me. So I went back to using dongles, with the Questyle M15 taking the prime place in my inventory. A dongle isn’t a perfect replacement for a DAP, so I kept looking. Imagine, then I stumbled upon FiiO representatives at the CanJam in London. After a short back and forth we have reached an agreement, and the FiiO M15S has landed in my hands, together with something else, but that’s a story for another time. 

Why do I like DAPs so much, and why a dongle can’t replace it you ask? A couple of reasons. I value the independence of music from my phone. Also, listening to music doesn’t drain my phone’s battery. Great for longer trips. Then, the sound quality. Physically larger device means we can put more stuff inside. And in this scale, the more the better. Reviewed FiiO M15S features one of the top DACs on the market, the ESS Sabre ES9038PRO, which by itself is just huge. It by itself is as wide as a dongle I used for comparisons in this review. Lastly, output power. Less important with IEMs, as dongles can handle that very well, but with headphones, extra headroom makes all the difference. 


FiiO M15s packaging, unboxing

Unboxing feels like it’s a premium smartphone. Or, like it’s the M11 PLUS with extra steps. Everything we get is packed very nicely and securely. The external sleeve is full of iridescent prints. Looks cool, like it’s a gaming accessory.

Inside, we’ll find the player in a hard foam piece. Underneath them you’ll find the DK3S stand with a cooling fan, quick start guide and USB type C/Type C- Type A cables. I like the idea of the stand, as it complements the FiiO M15S as a desktop DAC/AMP. Even without running the fan, it’s just convenient to use, instead of a DAP lying flat on the desk. Reviewed FiiO M15S is delivered with a leather case, featuring a metal backplate for heat sinking. Cool, nobody wants to order that separately, especially at this price point. 

So, overall: all is good here, nothing to complain about. 

Build Quality

The first thing you should do when unboxing this DAP is to take it out of the case it comes in. The build quality is immaculate. I dare you, to find something imperfect.

It’s okay, I’ll wait.

Told you.

It looks great: metal frame, with perfectly fitted front screen and back glass. Tactile buttons, smooth knob on top, and a necessary hold button. The top knob is specially braced in case the DAP drops on top of it. It should survive that incident, but I haven’t tested this theory. I have a strict don’t drop stuff policy, but you can try if you want. Thermals are really good too. The internal heat spreader works nicely, heating the chassis pretty evenly, though the lower part is slightly warmer. Nothing worse than accidentally touching a hot spot on a DAP or smartphone, am I right?


Reviewed FiiO M15S is a DAP, which means this is going to be a long paragraph. Let’s start with the system part, and then we will finish with audio-related topics. The first thing we see is the 18:9 5,5” 720p display. While it’s nothing to write home about when compared to contemporary smartphones, it’s still a solid display. Vivid colours, brightness and resolution are enough for usage. To be honest I thought it was a higher resolution. Good thing I don’t review video gear then.

The brain of the reviewed FiiO M15S is the Snapdragon 660 featuring 4x 2,2GHz and 4x 1,8GHz cores, with an Adreno 512 graphics core is an older, but still capable SOC. It’s been used in phones like Xiaomi Redmi Note 7s, or Samsung A9. It uses 4GB of RAM and has access to 64GB of internal memory (some of which is taken by the operating system). The memory can be extended with a micro SD card, of a capacity of up to 2TB. Since no reputable brand makes cards this big, we’ll have to stick with a realistic 1TB, which is still absolutely insane.

All of this tech runs on a custom Android 10 with global SRC disabled. It means, it basically is bit perfect regardless of what app are you using. As was pointed out by my friend, Grzesiu, an older Android is not as secure as the newest versions with current security patches and features. Something to consider.

Built-in BT is done with the Qualcomm QC5124 Bluetooth 5.0 chip. It allows to use of the nicest codecs like LDAC, aptX HD, and AAC in both ways: as a receiver and a transmitter. On board, Wi-Fi supports both 2.4GHz and 5GHz bands in a Wi-Fi 5 spec. The power for all of that goodness comes from a 6200 mAh battery, which you can top up in around 4 hours, thanks to QC3.0 and USB PD.

Dope. You can set the battery limit at 80% to extend its life, a great feature! Nothing more annoying than searching for not only the right battery but also a repair shop that will handle a DAP a couple of years from now. 

For the audio part, inside the reviewed FiiO M15s we have a proprietary digital filter/SRC stage using an FPGA with a femtosecond oscillators from the Japanese NDK company. It also produces the SPDIF output you can access via the 3,5mm jack. The D/A conversion is done with an ESS Sabre ES9038PRO. Yes, the full-size version. It is interesting to me, how they managed to fit it inside this DAP. Kudos to that, not an easy task.

The analogue stage uses OPA927 opamps. The audio chain uses high-quality thin film resistors and metalized foil caps from Panasonic. We are getting a set of standard outputs: 3,5 mm and balanced duo: 2,5mm and 4,4mm. The first one can work as headphone out, line out and SPDIF out. Balanced outputs are either pone output or line level. A great feature for integrating the reviewed FiiO M15S into a stationary system. The USB connector works both ways allowing this unit to either feed an external DAC or become a USB DAC itself. The HiRes functionality is here with capabilities of up to 32bit/384kHz and DSD256. Is it the most you can get nowadays? No. Should you be bothered by that? Oh no, I won’t be able to listen to my collection of 768kHz music. Which is one sample file, which I never actually played.

The power output is respectable, with up to 1,2 W @ 32 Ohm @ 1% THD @ balanced out in Ultra High Power mode. It isn’t available for portable use, where we can expect a pretty nice 1 W @ 32Ohm @ 1% THD @ balanced out. Around 800mW with a reasonable distortion. A bit more than half of that with single-ended output. More than enough for IEMs and headphones. It’s not like I’m commuting to work with Susvara on my head, let’s be realistic. 

Desktop mode/high power

Charging the reviewed FiiO M15S is not as easy as you would expect. Let me explain. When connecting a regular USB power supply, it will charge like any other thing on this planet. But, if you plug in a fast charger with QC/PD functionality, you will get some extra options. First is the Desktop Mode. It disconnects the battery completely (neither charges nor drains), meaning the USB power supply takes full responsibility for the device. It basically turns into a desktop device. If you use the M15S at home it will hugely extend the battery life. 

The Ultra High Power Mode uses external power to increase the voltage rails from +/-6V to +/-7,6V bipolar, giving us around 3V of extra swing. It means that we have more headroom for the DAC part and more output power for the headphone amplifier. It’s an absolutely brilliant idea and it gives it more edge against other DAPs in stationary roles. Also, unlike its older brother, the reviewed FiiO M15s has no external power brick required. Just a modern USB power supply, which you most likely already have. How does it affect the sound? It is easy to notice. The music feels more dynamic and open. Sound staging gets wider and bass gets a nice boost. When listening at home, using this mode was a no-brainer.

User interface/features

The operating system of the FiiO M15S, being a custom Android 10 will feel familiar to most of us. Navigation is very intuitive as usual. All of the important settings are available in the easily accessible top menu. This DAP offers us 5 modes of operation:

  1. Android Mode: Regular, Android-based DAP with access to Play Store and 3rd party apps. 
  2. Pure Music Mode: skeleton OS functions and only the FiiO music app is available. Shuts down unnecessary processes and programs in the background. The “Audiophile mode” if you may.
  3. USB DAC Mode: exactly as stated (volume works?, HID?)
  4. Bluetooth Receiving Mode: turns it into a BT audio receiver, and shuts down everything else.
  5. AirPlay: works as an AirPlay receiver. Duh.

Most of my listening tests of reviewed FiiO M15s were in mode 1. 

An exciting feature for me is the FiiO Roon, which turns the reviewed FiiO M15S into a Roon Ready streamer. Works flawlessly, there is even an icon of this DAP in Roon. A fantastic option for those who want to share this device between home and portable use. As an avid Roon user, I’m content. Also, the buttons on the player control Roon, so you can easily skip tracks. 

The menu holds another audiophile feature: upsampling to DSD64 2,8MHz. It uses the built-in FPGA to convert every input to DSD before it is converted by the onboard DAC. Besides “cool kids factor” it makes the sound a bit softer, smoother and slightly less dynamic. Also, drains a battery like crazy, so be mindful of that. Cool thing to have, similarly like it was in the M11 PLUS. 

There is one multifunction button on the side. By default, it allows for quick mode selection, but you can customise its function, including switching filters, adding to favourites, switching songs randomly and a couple more. A convenient thing to have, but when using the switch filter function I was getting no info on which filter I was using. I would have to go into audio settings to check which one is being used now. Shame, it’s not displayed anywhere else. Nothing a patch won’t fix FiiO.

The last trick I want to talk about is the second harmonic regulation, a feature built into the ES9038PRO chip. It allows us to increase the amount of second harmonic in the output signal. Make the sound more tubey and sweet. In practice it felt like a bit of extra compression, softening the sound and dynamics. I preferred listening without it, as level 1 was hard to notice and level 2 was a bit too much for me. 

Sound of the reviewed Fiio M15S

Reviewed FiiO M15s with Craft Ears Aurum

To kick things off, FiiO M15S sounds different than most ESS-based audio devices. So that’s exciting (at least for me). It has a focus on midrange, pushing it forward. The exact opposite of a V-shaped response. The first things that came to mind after listening to it were spectacular sound staging and dynamics, which I admit sounds like any other review about gear with ESS DAC. I know. Not much I can do about it. On a more serious note, the sound quality from the M15S is spectacular for its price. It was able to stand up to a few really good competitors in portable and desktop realms. 


When we think of ESS Sabre devices we usually think about spectacular bass. Well, not in this case. It plays a supporting role, taking a backseat. It provides enough quantity to provide a foundation but certainly is not a star of the show. It provides a solid level of resolution when listening to Afghan Whigs – Gentlemen. The bass riff in the background is crisp and separated from other instruments. Drums were tight, and snappy, with a great natural reverberation. Something I like a lot in sound. The textures are on point and while the bass sounds a bit light to my taste it does deliver quality noise.


This is where the party’s at. If you like huge, bold vocals and guitars, you’ll be delighted with the reviewed FiiO M15S. It puts the midrange on a pedestal and pampers it to no end. It is the most prevalent with vocals, both male and female. The singers/rappers/growlers seem to be physically imposing and they speak to like you are the only person in the world. I don’t want to ride the hype, but I can’t mention Oliver Anthony’s Rich Men north of Richmond. If you listened to this song even once, you know that besides hitting the nail on the head lyric-wise, it also is recorded very poorly. Nosie, clipping only adds up to the message. It fits with him being an off-grid artist, recording on a field outside his home, singing his heart out. It makes sense. And when you listen to it on the M15S, it speaks straight to your soul. As with other ESS-based DACs, the tonality could be richer (like men north of Richmond) it still is an excellent display of capability, especially if you love the clean, uncoloured, exact presentation.


I’ve been listening to Robyn’s Missing U, which has a lot of bells and I have noticed that they really stood out to me. The M15S treble is terrific. It blends resolution, speed and precision while not falling into metallic quality which can happen with ESS-based DACs. Bells in the mentioned song spread out all around my head evenly, creating a really immersive performance. They are a bit behind midrange, so take that into consideration when selecting your headphones/IEMs, more on that later. All in all, the FiiO M15S reproduces treble with great vigour, highlighting its detail.

Sound staging

Sound staging is very impressive here, although it has some quirks to it. Let’s start with the elephant in the room: vocals. They tend to be set dead centre with a tendency to be very big in size. It empowers the vocalists’ performance to a huge degree. Listen to Stir it up by Bob Marley & The Wailers, you’ll understand what I mean immediately. Bob and the choir are slightly exaggerated, while the rest of the bands feel very natural with a very wide and decently deep soundstage. The deepness seems to be limited by the dominating midrange in the middle. It creates this uncommon, but very fun vocal-centred presentation.


Sadly, at the moment I only got my hands on ESS-based devices, so the differences aren’t going to be that big. There is a lot in common between those. I hope to expand my choices in the future, but for now, it is what it is. It’s also a great mirror of how the market was shaped by the fire of the AKM factory. To end on a positive note, I’m excited to see that Cirrus Semiconductor is still a pretty popular choice, AKM is getting back into the game, and we have a new player in the audio DAC game, namely ROHM from Japan.

FiiO M17

The difference between those two was much bigger than I was expecting. I was thinking: same manufacturer, same chip… Well, FiiO said hell no! The M17’s sound signature is a v shape with extra emphasis on the bass. It’s big and thick, just like me. It’s a big contrast to reviewed FiiO M15S’s midrange forward sound. The bigger brother does sound better, but is it “I’m going to carry this brick around like I’m a slave in a quarry? Don’t know. If I was travelling a lot, and staying in hotels a lot… Yes. It would be my audio centre, able to perfectly drive regular headphones with its superior output power. In my case, travelling to work, or domestically (and not that often) I prefer the FiiO M15S. It is still a great desktop device if need be, but has a much better carry-ability factor. It fits into either a pocket or a fanny pack. 

The M17’s bass is much more prevalent and dominating. It does that while preserving the control and resolution of its younger brother. It’s going to knock your socks off, and you’ll come back for seconds. The midrange is my opinion a bit less pleasant than in the FiiO M15S. Smaller DAP has more finesse and agility. Human voices seem more open and engaging. The resolution and scale are once again on Big Boi’s side. To top things off, treble is similar in both cases. The M15S might come across as slightly metallic, while the M17 is much more neutral and less offensive. 

JDS Labs Element III

As you know, I was really impressed with Element III’s mature sound and great feature set. It felt only right to compare it with the reviewed FiiO M15S in desktop mode, after talking so much about how it functions. So, I put the Ultra High Power mode on and switched to 3,5mm connectors to even the playing field. For ease of you, the JDS takes the point. A simple, fast user interface provides everything you need in 2 or 3 moves of a hand. With the reviewed FiiO M15S it takes a bit longer, because of how many functions there are. Speaking of which, the DAP takes the point here. While EIII is only a DAC/AMP, the hero of this review does everything from BT, AirPlay, local files and streaming. And is a solid DAC/AMP on top of that. Sound-wise, the M15S takes the cake. It is clearly a superior-sounding device. While the EIII has a more balanced, universal sound to it, the competitor takes the whole thing to the next level. Might be the jump from portable ESS9018K2M to major league ES9038PRO. The DAP provides more resolution, more open sound, and better sound staging. It also has its own style which might be a pro or a con. Depends on you. In terms of driveability, the EIII can do more, but in most cases, the difference wasn’t huge. Of course all of the extra options and better sound cost more.

Questyle M15

I had to compare the two. First of all, a dongle vs a DAP is a discussion that never ends. The Questyle’s dongle is one of the best on the market. Secondly, THE COINCIDENCE: Questyle M15 and FiiO M15S? Come on, I couldn’t let that pass unnoticed. So, do the differences justify the price jump between the two? The answer is not so straightforward as yes, or no. It comes down to your needs and lifestyle. Is the reviewed M15S a reasonable choice for people who use IEMs on a commute to work? Unless you are chasing the last ounce of sound quality – probably not. On the other hand – if you travel more, or use it in your home system, the extra investment seems to be a no-brainer. 

Sound-wise the DAP is significantly more capable – which shouldn’t be a surprise to anybody. The dongle hides detail and feels a bit choked up in comparison. The dongle does better in terms of the amount of bass, which might be a deciding factor, for those, for whom the M15S feels too bass-shy. To be fair when I listen to the M15 it feels like it’s a great sound and I don’t miss anything. Then, when I switch to the M15S… Yeah, there it is.


Meze Liric

Meze Liric is considered one of the best closed-back headphones on the market and you can’t understand how much I wanted this set to work. Super comfortable headphones, with a capable DAP, it had to work. Well, it doesn’t exactly. The Meze’s child has a tendency to be shouty around the mids/treble border. The M15S like to push the midrange forward. It gets shouty and sibilant on some tracks. Too much for me to be honest. Imagine how heartbroken I am, when I wanted to buy the Liric for personal use with this DAP. Sadly, while both are great products, they aren’t made to work together.

Craft Ears Aurum

The previous flagship from Craft Ears, the Aurum is a great match to the M15S. Its slightly V-shaped response matched the M15S character. Together they make an amazing set in which the midrange still dominates but it is compensated by punchy bass and crisp, fresh highs. It’s a very fun-centred setup, which shines in all genres. The notable moment for me was when I was listening to mentioned earlier Rich Men north of Richmond. The effect of his raw voice was multiplied by this combe to a bone-chilling effect. A truly spectacular show of capability.

HiFiMan Sundara Closed

While not exactly portable, the Sundara Closed is a great headphone. After my disappointment with Liric, it was my next obvious choice and boy it didn’t disappoint. Together with the M15S, it presented a fresh, surprisingly open sound. Lighter tonality and excellent tight bass are the name of the game here. I love the detail retrieval from this combo. The M15S drives the Sundara Closed with ease, even without the Ultra High Power mode on. With it, it’s even better. Both work great even at louder settings, with no lack of headroom. No choking up, just music. It’s a testament to a great amp that is used in the M15S. 

Fiio M15S Review – Summary

Well, what can I say? Another really good DAP from FiiO. The value for price is very strong here. We get a terrific sounding source, that can handle any IEMs and many headphones.

Its sound signature is midrange-focused with excellent resolution and dynamics. On top of that, we have a set of thoughtful features that actually make a quality of life difference. Battery saving, extra power with USB PD/QC chargers, multiple modes dedicated to different uses. I can see the M15S becoming a part of many people’s lives both at home and outside. If you are in a market for a capable DAP, give the newest FiiO a shot. It’s worth it.


Big thanks to Fiio for providing the M15S for this review. I wasn’t paid or asked to say anything good or bad about this product, all of the above is just my personal, unbiased opinion.