Portable R2R player FiiO M33 Gold

Portable R2R player FiiO M33

The FiiO M33 is a portable music player built on an R2R architecture that focuses on a more natural and musical sound compared to conventional delta-sigma converters. It is based on precise voltage steps and natural timing, commonly associated with a more "analogue" reproduction character. The fully differential 24-bit R2R resistor ladder uses 192 precision thin-film resistors with 0.1% tolerance, delivering exceptionally clean and balanced sound with emphasis on dynamics, space and naturalness. There is also the option to switch between OS and NOS modes, where you can choose oversampling for higher accuracy or non-oversampling for a more direct signal path and a more authentic reproduction character. The M33 is therefore not just an ordinary player for listening on the go, but a fully fledged audiophile source capable of replacing a high-quality desktop DAC and headphone amplifier.

From a desktop R2R DAC to a portable player

FiiO has integrated its proprietary R2R architecture, originally developed for desktop audio equipment, into a compact portable player for the first time. The result is a combination of the typical analogue character of R2R converters with a modern portable solution for everyday listening at home and on the move. The M33 also offers a special desktop mode with a pair of USB-C ports that separate power from playback to minimize interference and provide more stable sound during prolonged use. Thanks to this it can serve not only as a portable player but also as a fully capable desktop DAC and preamplifier for a home audio system. The built-in 4400 mAh battery offers up to 15.5 hours of playback and supports fast 30W charging with an emphasis on low heat generation during charging.

Android 13, Snapdragon 680 and flagship headphone amplifier

At the heart of the FiiO M33 is an octa-core Qualcomm Snapdragon 680 processor paired with 8 GB of RAM and the Android 13 operating system, ensuring smooth operation of the system and streaming apps. The large 5.5" Full HD display with 1080 × 2160 px resolution provides clear control, a modern user interface and visualizations inspired by classic Hi‑Fi components. Performance is driven by a fully differential headphone amplifier using top-tier TI Burr‑Brown components including OPA1637 operational amplifiers and a quartet of INA1620 amplifier chips. Symmetric output power up to 1100 mW + 1100 mW into 32 Ω can easily drive sensitive IEMs as well as demanding high-impedance over-ear headphones. The analogue section uses separate power supplies for the digital and analogue sections, multi-level shielding and Rubycon film capacitors for the cleanest possible signal, low noise and stable sound even under heavy load.

Hi-Res audio and modern connectivity

The FiiO M33 supports high-resolution playback up to 384 kHz / 32 bit and DSD256 for local playback, and in USB DAC mode it handles up to 768 kHz / 32 bit and DSD512 thanks to a dedicated XMOS XU316 USB chip with ultra-low latency. This chip ensures not only stable signal transfer but also precise audio synchronization when used with a computer or laptop. Bidirectional Bluetooth with support for LDAC, LHDC, aptX HD and aptX Adaptive is standard, allowing wireless streaming in significantly higher quality than typical Bluetooth. Symmetric and unbalanced headphone and line outputs, USB audio and a coaxial SPDIF output are available, so the M33 can function as a portable player, desktop DAC, preamplifier or digital transport for external audio systems.

Key features

• Portable Hi‑Res music player with FiiO's proprietary R2R architecture.
• Fully differential 24‑bit R2R resistor ladder with 192 precision thin‑film resistors.
• OS / NOS modes for choosing between oversampling and a more direct signal path.
• Qualcomm Snapdragon 680 processor and Android 13 operating system.
• 8 GB RAM and 128 GB internal storage.
• Supports microSD / TF cards up to 2 TB capacity.
• 5.5" Full HD display with 1080 × 2160 px resolution.
• Dedicated XMOS XU316 USB chip with ultra‑low latency.
• USB DAC up to 768 kHz / 32 bit and DSD512.
• Local playback up to 384 kHz / 32 bit and DSD256.
• Symmetric power up to 1100 mW + 1100 mW into 32 Ω.
• Four gain levels including a mode for demanding over‑ear headphones.
• TI Burr‑Brown OPA1637 op amps and INA1620 amplifier chips.
• Rubycon film capacitors and separate power for digital and analogue sections.
• Multi‑level isolated shielding to minimize noise and crosstalk.
• Balanced 4.4 mm and unbalanced 3.5 mm headphone outputs.
• Balanced and unbalanced line outputs for connecting an external amplifier or active speakers.
• USB audio and coaxial SPDIF digital output.
• Bidirectional Bluetooth 5.0 with support for LDAC, LHDC, aptX HD and aptX Adaptive.
• Supports streaming apps as well as a local music library.
• Desktop mode with separate power and playback via a pair of USB‑C ports.
• Can be used as a portable player, desktop DAC, preamplifier or digital transport.
• Built‑in 4400 mAh battery with up to 15.5 hours of playback.
• Fast 30W charging with temperature optimization during charging.
• Elegant construction with AG glass and minimalist design.

Evaluation

• FiiO