The FiiO M21 is an audiophile player equipped with four Cirrus Logic CS43198 digital-to-analog converters in a matrix configuration. It offers balanced amplification delivering up to 950 mW per channel and features a desktop mode, allowing it to be used as a fixed audio source. The device has a 4.7-inch touchscreen and a design inspired by Walkman players, with playback compatibility up to 384 kHz / 32 bits.
The M21 takes a unique technical approach with its four Cirrus Logic CS43198 chips arranged in a matrix configuration. This eight-channel architecture aims to minimize crosstalk between the left and right channels while reducing background noise. Signals pass through an I2S interface driven by an internal FPGA and a dual quartz oscillator to stabilize the clock.
Amplification follows a two-stage logic: the first handles voltage amplification, the second current expansion. This separation of functions provides extended dynamics and preserves tonal richness. Three gain levels adapt to the characteristics of the paired headphones.
The machined aluminum alloy chassis features a frosted, anti-reflective glass back. The dimensions of 121 × 68 × 17 mm and a weight of 193 grams provide a reassuring density without compromising portability. The 4.7-inch IPS screen includes an oleophobic coating. Two dedicated USB-C ports separate functions: one for data and charging, the other for desktop mode.
Desktop mode is the M21’s standout innovation. By connecting an external power supply to the second USB-C port, the device completely bypasses its internal battery. This setup delivers up to 21 Vpp peak with 950 mW per channel at 32 ohms. The external power supply eliminates potential battery interference, turning the M21 into an audio source for home hi-fi systems.
This mode also activates the Super High gain, which is inaccessible when running on battery. Battery protection prevents any charge-discharge cycles when the external power supply is active, thus preserving cell longevity. This feature caters to users seeking extended listening sessions without battery life constraints.
The M21 offers two simultaneous headphone outputs: unbalanced 3.5 mm jack and balanced 4.4 mm jack. Each output can be switched to line level to feed external amplifiers. The SPDIF coaxial output via the 3.5 mm jack allows connection to external converters.
Bluetooth 5.0 connectivity is bidirectional. For transmission, it supports LDAC, LHDC, aptX HD, AAC, and SBC codecs for wireless listening. For reception, it turns the M21 into a Bluetooth receiver, compatible with AirPlay for Apple devices. This versatility extends usage scenarios beyond simple local file playback.
The Android 13 system, optimized for audio, bypasses the limitations of the standard operating system. Integration of the Google Play Store allows installation of streaming apps: Qobuz, Tidal, Apple Music, Spotify, Deezer. The eight-core Snapdragon 680 processor ensures smooth navigation even with the most demanding applications.
The 4000 mAh battery provides a measured battery life of 15 hours on the unbalanced 3.5 mm output and 12.5 hours on the balanced 4.4 mm output. These values correspond to standard use with high-resolution local files. Fast charging via PD 2.0/3.0 up to 20 W through USB-C reduces downtime.
The dual power supply system is a notable technical asset. In portable mode, the electronics draw from the battery as needed. In desktop mode, the external power supply takes over completely, isolating the battery from the circuit. This approach preserves the cells from unnecessary cycles while ensuring stable power for high-power amplification.
The M21 runs on Android 13 with access to the Play Store, unlike the JM21 which uses FiiO’s proprietary system. The M21 also features desktop mode for stationary use with an external power supply.
Desktop mode delivers higher power (950 mW per channel) and activates Super High gain. The external power supply eliminates battery interference and allows for unlimited listening time.
The M21 decodes PCM files up to 384 kHz/32 bits and DSD files up to DSD256. It also supports built-in 8x MQA decoding.
Yes, the M21 can transmit to Bluetooth headphones (LDAC, LHDC, aptX HD) and receive from smartphones or computers. It is AirPlay compatible for Apple devices.
Battery life varies depending on the output used: 15 hours on the unbalanced 3.5 mm jack, 12.5 hours on the balanced 4.4 mm jack. These figures correspond to listening to high-resolution local files.
The 64 GB of internal storage (52 GB usable) can be expanded up to 2 TB via microSD card. The Android system also allows streaming from music apps.
Yes, the M21 works as a USB DAC up to 384 kHz/32 bits. It can drive headphones or serve as a source for a hi-fi system via its line or coaxial outputs.
Dominique
I was very happy with this device, until the screen started glitching from time to time, and more and more often!
Comment from May 29, 2026 — Experience from September 28, 2025
Tshab
The best companion for listening on the go to your favorite sounds in the most demanding formats without breaking the bank.
Comment from May 13, 2026 — Experience from December 29, 2025
Dominique
Magnificent, I'm delighted 👍👍👍👍
Comment from May 07, 2026 — Experience from April 25, 2026
