Out of the box, the M3K looks and feels like a very modern update of the original iPod mini. It’s small and light by any standard, with a silver all-aluminum housing with rounded edges; it feels extremely comfortable and sturdy in the hand. A silicone case is included, but we prefer the M3K naked. Where the iPod mini had a modest monochromatic display and resistive clickwheel, the M3K has one large piece of glass (with screen protector pre-installed) that features a 240×320 IPS LCD display (non-touch) and capacitive touch control area. The display is admittedly small (album art is displayed at about 1.75 inches), not terribly bright, and lacking the extreme viewing angles of modern smartphone displays, but is certainly adequate for this application. Physical power, track, and volume controls are located on the left side of the M3K — they’re clicky, but without a “Hold” button, they are sometimes accidentally pressed when the M3K is stored in a pocket. All the M3K’s ports are located on the bottom, including a 3.5mm headphone jack, a microSD slot, and a micro USB port. We would have liked to see USB-C like on Fiio’s BTR3, but at this price point we don’t expect the newest of everything. Our only real design critique is that the M3K would have been more pocketable with a wider, thinner form factor rather than the chubby 2004-esque rounded rectangle.
Unlike Fiio’s M7 and X7 that run Android, the M3K runs a customized Linux OS. Its interface is an improvement on that of Fiio’s X3 MkIII, greatly simplified to focused on music playback with just one extra feature — audio recording — for added flavor. Navigation through folders is accomplished with simple up/down/left/right swipes and taps. Some notable features are absent here: the M3K has no Bluetooth, bass boost, gain control, hardware button lock, or lyric display.
What remains, however, is all the important stuff. The M3K’s 1Ghz processor is snappy and responsive (although album art can take a few seconds to load), and its AKM AK4376A DAC can decode just about any file format you can imagine, in resolution up to 32bit / 384kHz PCM or DSD64, and is Hi-Res Certified. Gapless playback is, thankfully, still present, and a basic 5-band equalizer is included with a few presets. The M3K can also function as a USB DAC, though playback is limited to 24bit/192kHz and there is no Line Out mode available. Its battery life is excellent; Fiio claims up to 26 hours of playback and 38 days of standby and we believe it, since we were able to go through the entirety of our testing over two weeks on a single charge. The M3K has enough power for just about any headphone you could realistically expect to use with it — Fiio quotes 25 mW into 32 ohms and 42 mw into 16 ohms. All the IEMs we tried with the M3K were adequately powered, though some 25- and 32-ohm headphones needed to crank the M3K up to about 75% of its max for the same volume.
Most importantly: the M3K sounds good, especially considering it’s low price, and was noise-free even with sensitive IEMs. We wouldn’t say it’s the most neutral player we’ve heard — its presentation is a bit warm — and we have heard better detail retrieval out of Fiio’s higher-end DACs and DAPs, but the M3K never disappointed us in our testing. The M3K might not match Fiio’s expensive flagship players, and there are certainly some software features that we wish would be added but, viewed as a complete package, we don’t think the M3K is trying to unseat players 10x its price. Rather, we see the M3K, with its metal and glass body and Hi-Res decoding as a welcome elevation of budget DAPs. If your budget is tight and you’re looking for a high-quality DAP, we think the Fiio M3K is a solid choice.