FiiO is continuing its steady rollout of desktop audio gear with two new products aimed at headphone users building or upgrading a compact hi-fi system: the DARKSIDE PRO linear power supply and the K13 R2R DAC/headphone amplifier.

While the two devices can be used independently, they’re clearly designed to complement each other, one focusing on cleaning up power delivery, the other handling digital conversion and amplification.

Power supplies aren’t usually the most exciting part of an audio setup, but they can have a measurable impact on how a system performs. The DARKSIDE PRO is FiiO’s latest attempt to address a common weak point in many desktop systems: basic switching power adapters.

Instead of relying on a standard wall wart, the DARKSIDE PRO uses a linear power supply design, which is typically better at minimizing electrical noise and interference. That matters because any noise riding along with the power can end up affecting sensitive components like DACs and headphone amplifiers.

At the core of the unit is a 75W toroidal transformer, paired with a fully discrete voltage regulation stage. This combination is designed to deliver stable current with low ripple, even when connected devices demand more power during dynamic playback.

Key features include:

• Selectable 12V or 15V output
• Up to 3A of current
• Low-noise, low-ripple power delivery
• Compatibility with a wide range of DACs, amps, and streamers

The ability to switch voltage makes the DARKSIDE PRO more flexible than typical bundled adapters, allowing users to better match the requirements of their gear. It’s not limited to FiiO products either—any compatible device within those voltage and current limits can benefit.

In practical terms, a cleaner power source can help reduce background noise and improve overall system stability. Rather than changing the sound signature, the goal here is to remove interference so connected components can operate closer to their intended performance.

The DARKSIDE PRO is scheduled to launch in April, priced at $159.99 (£139.99 / €159.99).

Alongside the power supply, and after initially announcing it in September last year, FiiO has introduced the K13 R2R, a desktop DAC and headphone amplifier built around a resistor ladder (R2R) architecture, something still relatively uncommon at this price point.

Most DACs in this category rely on delta-sigma chips, which are efficient and widely used. R2R designs take a different approach, using arrays of precision resistors to convert digital signals into analog output. In this case, FiiO is using a fully differential 24-bit R2R design built from tightly matched thin-film resistors.

The K13 R2R integrates the entire signal chain into one unit:

• Digital-to-analog conversion
• Volume control
• Headphone amplification

All of it runs through a fully balanced signal path, which helps reduce distortion and improve channel separation.

Here’s a breakdown of what it offers:

• Up to 2400mW + 2400mW (32 ohms) output power
• Multiple gain settings for IEMs and full-size headphones
• Support for NOS (non-oversampling) and OS modes
• USB (up to 384kHz/32-bit PCM, DSD256 via XMOS)
• Optical, coaxial, and I²S inputs
• Bluetooth 5.4 with LDAC for wireless streaming
• Balanced and single-ended outputs
• Built-in display showing sample rate, volume, and output mode
• 10-band parametric EQ via the FiiO Control app or browser

The inclusion of both NOS and OS modes gives users some control over how the DAC behaves. NOS mode typically prioritizes a smoother, more continuous presentation, while OS mode leans toward a more precise, technically detailed output.

The amplifier section is designed to handle a wide range of headphones, from sensitive in-ear monitors to more demanding planar designs, thanks to its relatively high output power and balanced architecture.

The K13 R2R is available now in black or silver, priced at $319.99 at Amazon (£279.99 / €319.99).

What ties these two products together is the idea of treating a desktop setup as a system rather than a collection of individual components.

The K13 R2R handles the signal path, from digital input to analog output, while the DARKSIDE PRO focuses on the quality of the power feeding that chain. FiiO positions the pairing as an upgrade path for users who want to improve performance without replacing everything at once.

There’s also a broader point here. Many DACs and headphone amps in the entry-level and mid-tier range ship with basic switching power supplies. They work, but they’re not always optimized for low-noise audio applications. A higher-quality external power supply can sometimes make a noticeable difference by reducing interference and maintaining more consistent voltage under load.

That’s the gap the DARKSIDE PRO is intended to fill.

With the DARKSIDE PRO and K13 R2R, FiiO is targeting users who are building or refining a desktop headphone setup rather than chasing an all-in-one solution.

• The K13 R2R focuses on DAC architecture, amplification power, and connectivity.
• The DARKSIDE PRO addresses power delivery, which is often overlooked but can influence system performance.

Neither product reinvents the category, but together they highlight a more system-level way of thinking about desktop audio, where both signal processing and power quality play a role in the final result.

Related Reading:

• Forget Chip DACs—FiiO’s K13 R2R Uses Resistors to Change the Game
• FiiO’s $30 Headphones Look Straight Out of the ’80s — But They’re Hiding Modern Audio Tech
• FiiO Just Dropped a $600 R2R Music Player at CES 2026 — And It’s Unlike Anything Else in Its Class
• FiiO's Snowsky Disc Is a Bluetooth DAC, Music Player, and CD Throwback All in One
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