I tried FiiO's M15S hi-res audio player and it's a musical powerhouse – even with cans

FiiO M15S with Beyerdynamic headphones, on a coffee table
(Image credit: Future)

FiiO is a name that's often said in the same sentence as "hi-res audio player" and "Astell & Kern" – and its latest player, the FiiO M15S, is easily the best FiiO player I've got my mitts on. 

We covered the M15S when it launched in March, but to recap: it features dual desktop-grade ES9038PRO DACs, support for up to 384kHz/DSD256 hi-res audio, MQA, Roon, aptX HD, LDAC and LHDC, plus 3.5mm single-ended and 2.5mm/4.4mm balanced headphone outputs.

And it does it all for $999 / £979 / (around AU$1,800), which is just a tad more than the excellent Astell & Kern A&norma SR25 MKII but a lot less than the newest A&ultima SP3000. A lot. Did I mention that the snug protective case, with a reassuringly snappy volume knob protector, is included? 

The M15S Digital Audio Player (often shortened to DAP in audiophile circles) builds on the success of previous award-winning portable audio equipment from FiiO, including the very talented FiiO MS11. Those dual DACs (one for both the left and right channel) each use four D/A converters, and as you'd hope, the M15S also supports files encoded using MQA, whether they're Tidal Master offerings or files in your own music library.

FiiO M15S with Johnny Cash on the screen, on a coffee table

Johnny Cash sounds especially earnest on this FiiO  (Image credit: Future)

The M15S is able to both transmit and receive hi-res audio thanks to aptX HD Bluetooth, LDAC, and LHDC wireless connectivity – something you won't find on even some of the best MP3 players (and definitely not on my beloved iPod Classic). This two-way connectivity means not only that wireless headphones are coming onboard, but the M15S can also receive audio from a smartphone, PC or other device, and it can be used as a Bluetooth DAC/Amplifier.

Oh, and plenty more wireless audio options are also available if you're not going the wired headphones route – aptX, aptX LL, aptX Adaptive to name but a few – while its onboard 2.4GHz/5GHz Wi-Fi allows for Apple AirPlay, DLNA streaming and Roon Ready connectivity.

Opinion: I still love Astell & Kern's brutalist build quality, but this thing has power and panache in spades 

FiiO M15S close-up to show the headphone ins and volume knob

The supplied case protects inadvertent volume tweaks (when listening to Lorde) with a snappy magnet strap (Image credit: Future)

Here's the kicker for me: by adopting the dual power supply option found on FiiO's flagship M17 DAP, the M15S operates without using the internal battery in its desktop mode, which means it's able to output 21% more power. And that means the Beyerdynamic T5 closed-back cans you see pictured at the top of this article (with their Tilted Tesla drivers) are driven with ease. I set the volume at 60 of 120 when listening to Meat Loaf's Bat Out of Hell, and I quickly had to turn it down. Surprising. 

To drill down into this a little more, the M15S can easily be manually adjusted to output five levels of gain, but when using internal battery power, 'low', 'medium', 'high' or 'over-ear' gain levels can be selected. When using external USB power, in desktop mode, the additional 'enhanced over-ear' gain level becomes available, delivering an impressive 1200mW per channel. Thus, all but the hardest-to-drive planar magnetic designs will work just fine here – and the best over-ear headphones will combine happily with the M15S. My beloved Audeze Euclid? Like a dream.

FiiO MS15 on its side, next to Beyerdynamic headphones

The FiiO MS15 is thicker than a smartphone, but if you have big pockets you'll get away with it… (Image credit: Future)

Also trickling down from the firm's flagship M17 is the Qualcomm Snapdragon 660 processor, and the M15S runs on the Android 10 operating system and features a global SRC bypass, meaning that music streaming apps such as Tidal, Qobuz, Apple Music and Deezer can be installed to allow listening in full lossless quality.

Elsewhere, you're getting 10.5 hour battery life, a 5.5-inch multi-touch HD display (which is crisp, clear and has very little lag), and onboard storage of 64GB. Want a little more room for all those DSD files? It's all good – the M15S also features a microSD card slot with support for up to 2TB cards.

Android device owners will also feel at home with this layout over certain other DAPs, the operating systems on which can feel a little cluttered or confusing.

Daniel Avery's Ultra Truth is expansive, nuanced and zealous; Johnny Cash's At Folsom Prison is textured and three dimensional. Radiohead's The Bends snakes seductively around your brain, never overstating Jonny Greenwood's axe or Thom Yorke's upper register. I could go on, but the best way to describe the M15S is simple to say it sounds really good

Becky Scarrott
Audio Editor

Becky became Audio Editor at TechRadar in 2024, but joined the team in 2022 as Senior Staff Writer, focusing on all things hi-fi. Before this, she spent three years at What Hi-Fi? testing and reviewing everything from wallet-friendly wireless earbuds to huge high-end sound systems. Prior to gaining her MA in Journalism in 2018, Becky freelanced as an arts critic alongside a 22-year career as a professional dancer and aerialist – any love of dance starts with a love of music. Becky has previously contributed to Stuff, FourFourTwo and The Stage. When not writing, she can still be found throwing shapes in a dance studio, these days with varying degrees of success.