M33 R2R Digital Audio Player

The FiiO M33 R2R brings FiiO’s own R2R resistor-array DAC, originally designed for its desktop equipment, to a portable player for the first time. Tuned by FiiO’s acoustic engineers and refined with feedback from audiophiles around the world, it combines the lush, analogue-like warmth associated with R2R with balanced, high-fidelity performance. Around it are a multi-stage TI amplifier with up to 1,100mW + 1,100mW, the M27’s DAPS digital audio purification system, Android 13 on a Snapdragon 680 with 8GB of RAM and 128GB of storage, a 5.5-inch 1080p screen, a 4,400mAh battery for up to 15.5 hours and a patented Desktop Mode for use at home.

Fully differential 24-bit R2R resistor arrays

Instead of a delta-sigma DAC chip, the M33 R2R converts with precision resistor arrays: four channels, fully differential, using a total of 192 precision thin-film resistors with 0.1% accuracy and low temperature drift. In local playback you can choose OS mode (upsampling to 352.8kHz or 384kHz, the default) or NOS mode (native sample-rate output), and two selectable sound profiles, Flat (natural) and Warm (warmer), shape the character.

DAPS: the M27’s digital audio purification system

The M33 R2R uses the same ultra-high precision, ultra-low jitter unified clock as FiiO’s flagship M27: a high-capacity FPGA with two custom femtosecond oscillators (45.1584MHz and 49.152MHz), which handles the OS/NOS processing and feeds the R2R arrays. FiiO says it is a big step up in digital processing efficiency and fidelity over the M23; the new FPGA has 4,480 logic units, 288.89% more than the previous one. The low-jitter coaxial circuit rivals dedicated digital transports, with jitter as low as 71.5ps.

A multi-stage audio circuit, powered by TI

Two TI Burr-Brown OPA1637 fully differential op-amps handle I/V conversion and signal conditioning for a natural, expansive soundstage, followed by OPA1662 low-pass filters and an NJW1195A precision volume control with very low noise. The output stage uses four TI INA1620 chips in parallel, which keep the channels free of interference even when driven hard, for up to 1,100mW + 1,100mW into 32Ω from the 4.4mm balanced output and 470mW + 470mW from the 3.5mm output. Eight Rubycon film capacitors give natural, transparent mids and smooth, fatigue-free treble.

Four gain levels, including super high gain

Choose low, medium, high or super high gain. Super high gain, FiiO’s over-ear headphone mode, appears when a PD2.0 or PD3.0 fast charger is connected to either USB-C port: it switches the amplifier to a higher-voltage supply, raising the balanced output from 900mW to 1,100mW per channel into 32Ω (and 240mW into 300Ω), enough for demanding high-impedance over-ear headphones.

A precision power supply and shielding

The digital and analogue stages have independent supplies, and the analogue stage has three separate circuits for the R2R arrays, the preamp and the amplifier, each with low-noise LDOs, for a more refined, natural sound. A 15W power management system, 65A high-current MOSFETs and large storage capacitors give ample headroom. The digital processing, R2R arrays, amplifier and power sections sit in separate, individually shielded zones, for a blacker background and a clearer soundstage.

Android 13 on a Snapdragon 680

A Qualcomm Snapdragon 680 (6nm, up to 2.4GHz) with 8GB of RAM and 128GB of storage (about 112GB available) gives smooth streaming and multitasking, with headroom for future updates; a microSD slot takes cards up to 2TB. Choose Android, Pure Music, AirPlay, USB DAC or Bluetooth receiver mode. A global 10-band PEQ works with FiiO Music and third-party apps, with AUTO EQ to match your headphones’ frequency curve automatically, presets such as pop, jazz and classical, and per-band tuning; global SRC bypass and All to DSD are system-wide too.

A 5.5-inch HD screen with cassette, spectrum and VU themes

The fully laminated 5.5-inch 1080 × 2160 screen, with an oleophobic coating and a pre-fitted tempered screen protector, is made for high-fidelity entertainment, and new cassette-tape, spectrum and VU-meter themes make every track more immersive.

A dedicated XMOS chip for USB

A dedicated XMOS XU316 gives ultra-low latency as a USB DAC (up to 768kHz/32-bit and native DSD512), so sound stays in sync with video on every device.

Outputs for headphones, speakers and DACs

The 3.5mm and 4.4mm outputs drive single-ended and balanced headphones (one at a time, in the order you plug them in), and switch to line outputs (2Vrms and 4Vrms) with dedicated line-amp circuitry for speakers and amplifiers; line-out volume can be fixed or adjustable. The 3.5mm socket also gives coaxial S/PDIF up to 384kHz/24-bit and DSD128, and USB audio output goes up to 768kHz/32-bit and DSD512, so the M33 R2R can feed an external DAC, or pair with FiiO’s DK1 PRO dock as a streaming transport. Two-way Bluetooth 5.0 transmits LDAC, LHDC, aptX HD, aptX and SBC, and receives LDAC and SBC.

4,400mAh, fast charging and Desktop Mode

The 4,400mAh battery gives up to 15.5 hours from the 3.5mm output or 13.5 hours balanced, longer than the M23, and low-temperature fast charging fills it in about 1.5 hours with a PD3.0 PPS charger. There are two USB-C ports: the USB 3.0 port handles data, charging and USB host/OTG, while POWER IN is for charging and power only. Switch on FiiO’s patented Desktop Mode (D.MODE, patent ZL202321946664.8) and the M33 R2R runs directly from USB power without charging or draining the battery, reducing charge cycles to extend its life. If the battery falls below 15%, it charges until full.

Slim, light and easy to hold

Like the M21, the M33 R2R has clean, minimalist lines: an 18:9 shape, dual-bevelled edges and an AG matte glass back, at about 258g and 17mm thick. A customisable multifunction button gives one-press access to features you use often, such as favourites, the EQ, USB DAC or Bluetooth receiver mode, or cassette mode. A leather case comes fitted: khaki with the retro gold version, colour-matched with dark blue and black.

It also pairs perfectly with FiiO’s SNOWSKY RETRO BOX cassette-style Bluetooth speaker (LDAC, 5W × 2), sold separately.

Good to know

• Super high gain needs a PD2.0/PD3.0 fast charger; other chargers charge normally (FiiO suggests 5V 1A or 2A).
• FiiO Link lets you control it from the FiiO Music app on a phone: over Wi-Fi or Bluetooth from Android, Wi-Fi only from an iPhone.
• Line output is at full volume unless you enable adjustable line-out volume, so unplug headphones before switching to it.
• See also FiiO’s M23 and its flagship M27.
• In the box: M33 R2R, leather case and screen protector (both fitted), USB data cable, quick start guide, warranty card and GPL V2 manual.