The FiiO M21 sits in the upper-mid tier of FiiO’s portable digital audio player range, positioned as a compact, high-performance device that brings together flagship-grade internal components at an accessible price. Drawing on technology developed for the well-regarded FiiO M23, the M21 is aimed at both newcomers to high-fidelity portable audio and experienced listeners seeking a capable, versatile daily player.
Design and Build Quality
The M21 features an aluminium alloy chassis paired with an anti-glare frosted glass back panel, giving it a premium feel in a compact and lightweight form. At 193g and approximately 68mm x 121mm x 17mm, it sits comfortably in the hand. The front is dominated by a 4.7-inch fully laminated display with 750x1334 resolution and an oleophobic coating to resist fingerprints and aid legibility in use. Each M21 ships with a distinctive cassette-style protective case that pays homage to the classic Walkman era, accompanied by a retro user interface and vintage sound effects that add a playful character to the device.
Audio Performance
At the core of the M21’s audio section are four Cirrus Logic CS43198 DAC chips configured in a fully differential eight-channel output arrangement, delivering dynamic, detailed, and interference-free audio reproduction. A dual-stage headphone amplifier provides both voltage and current gain, ensuring compatibility across a wide range of headphones from sensitive in-ear monitors through to high-impedance transducers. In super-high gain mode, the M21 delivers 950mW per channel into 32 ohms via the balanced 4.4mm output, with a signal-to-noise ratio of 126dB and a noise floor below 1.6 µV. Internal components include high-precision thin-film resistors and low-impedance tantalum capacitors, all selected to achieve clean bass, clear midrange, and natural high-frequency reproduction.
Streaming and Connectivity
The M21 runs FiiO’s customised version of Android 13 on a Qualcomm Snapdragon 680 processor with 4GB RAM, providing smooth performance across streaming platforms including Spotify, Tidal, and Qobuz, as well as high-resolution local audio files stored on its 64GB internal flash or a MicroSD card of up to 2TB. Bluetooth 5.0 is supported with LDAC, LHDC, aptX HD, aptX, AAC, and SBC codecs for high-quality wireless transmission to compatible headphones or speakers, and the M21 can also receive audio via LDAC, AAC, and SBC. Wired outputs include a single-ended 3.5mm socket (headphone output, line output, and SPDIF coaxial) and a 4.4mm balanced socket (headphone output and line output), plus a USB-C 3.0 port for data and charging and a second USB-C Power In port for desktop mode.
Desktop Mode and Battery Life
The innovative desktop mode allows connection to an external power supply via the dedicated Power In USB-C port, conserving battery life during extended home listening sessions while maintaining full output power. A 4,000 mAh battery provides up to 15 hours of continuous playback via the single-ended output (12.5 hours balanced), and the M21 supports USB Power Delivery 2.0 and 3.0 PPS fast charging to minimise downtime between sessions.
