FiiO K13 R2R

Retro sound, modern control — a pragmatic R2R you can actually live with

FiiO’s new K13 R2R is a fully balanced desktop headphone DAC/amp that embraces a true 24‑bit R2R ladder DAC while keeping the pragmatic feature set and price that made the K‑series so popular. In a landscape where many subjectivists find delta‑sigma (DS) DACs “too clean,” R2R has made a comeback — and FiiO has been at the forefront of accessible retro‑inspired hi‑fi, from tape players to R2R desktop DACs.

Having listened to K13 R2R and integrated it into my setup,I feel it offers something exceptional at its price point. You get both transparent OS (oversampling) and that R2R ‘NOS (non‑oversampling) modes’ that many will find compelling. NOS definitely leans into that nostalgic, “organic” warm R2R presentation that many listeners enjoy. Though, in summary,
I felt it sounded lovely with some of my older recordings. While OS aims to faithfully reconstruct the original signal — effectively indistinguishable from a good DS DAC in technical terms, yet here delivered by a discrete, fully differential R2R array.

Over the previous R2R from FiiO that I reviewed, it also brings a meaningful power bump and some great new features: a capable companion app with 10‑band PEQ and presets, a handy remote, balanced I/O, and the option to upgrade to a linear power supply. In short, it does exactly what it says on the tin, it is a substational upgrade over the previous K11 R2R. Given how clinical OS Mode sounds, while how ‘organic’ NOS sounds, I feel the K13 R2R does offer something unique at this price point.

But before we get into the detail’s let us look at the unboxing:

Unboxing and Build Quality

FiiO keeps the presentation tidy and protective, with a distinctly retro‑modern vibe.

The rear of the packaging lays out the headline features and connectivity.

Inside, everything is neatly organized and well protected.

Opening the box	Accessories compartment

Chassis fit and finish feel solid and purposeful. The top window with status lighting looks great on a desk, especially in dim light.

Here is the startup sequence and a quick video of the menu system:

Front and back

A quick tour of the unit from the front and back to highlight the display and connections.

Zooming in for more details:

Inputs and power	Line‑out options

XLR connectors	Full rear panel overview

I feel the XLR outputs is another great addition over the K11 (and justifies the extra size of the K13).

Accessories and Remote

A look at the included bits plus a closer view:

The Remote is another nice upgrade over the K11 R2R:

And the remote control allows you to control the navigate the menus on the display:

Fit and Desktop Ergonomics

As a desktop DAC/amp, the K13 R2R offers straightforward ergonomics: a clear front display, tactile controls, and easily accessible 6.35 mm and 4.4 mm headphone outputs.

It is larger than the K11/K11 R2R, so plan a bit more space on your desk, though not as large as the K15/K17:

Features and Performance

• Fully differential true 24‑bit R2R DAC resistor arrays
• OS and NOS modes for two distinct listening philosophies
• Substantial power output — up to 2400 mW into 32 Ω from the 4.4 mm balanced output (high gain)
• Companion app with 10‑band PEQ editing and many presets
• Dual USB‑C, optical, and coax inputs; RCA and balanced XLR line outs
• Remote control included (input/EQ/mode switching from the couch is addictive)
• Upgradable power — supports external linear PSU for those who want to squeeze out every drop

As a USB DAC on macOS, the K13 R2R supports high sample rates:

And it also appears as a bluetooth device on IOS:

I liked how once it was paired with IOS, the FiiO Control App worked perfectly allowing me to control the inputs and configure the PEQ via the app.

App control and PEQ

FiiO’s companion app offers input selection, EQ presets, and a full 10‑band parametric EQ so you can tailor the sound per‑headphone or per‑track.

Some of the other screens in the app:

EQ presets	Firmware update check

You can also configure the colour selection via the App:

Architecture highlights

I am a sucker for detailed audio-architecture diagrams:

These show a careful separation of domains (digital, R2R ladder, LPF, buffer, and headphone amp), with op‑amp choices that suit the task: OPA1642 for R2R/LPF and pre/headamp stages, LTA8092 for LO buffering, and TPA6120A for high‑current headphone drive.

FiiO also have an interesting overview showing the power supply differences:

Sound Impressions

The beauty of K13 R2R is that you can pick your flavor. In OS mode it aims for faithful reconstruction; in NOS it leans into that R2R ease and warmth. For testing, I used a range of headphones of my typical ’test’ headphones (Sennheiser HD600, HIFIMAN Edition XS, FiiO JT7) and IEMs (Crinear Protocol Max, Truthear Pure) to cross‑check behavior across impedances and sensitivities.

OS vs NOS, in practice

• OS mode: Presents a slightly warmer, more spacious image than many DS DACs I keep on hand, with clean transients and a well‑filled center image. If you’ve worried that R2R equals “soft focus,” OS mode will likely reassure you — it’s cohesive and articulate.
• NOS mode: Surprisingly linear tonally, but with a relaxed, unforced decay. There’s a touch more grain on leading edges and a slightly looser grip down low compared with OS; many will read this as “more natural.” I love that you can A/B and decide what suits the track, your headphones, and your mood.

Bass

Tracks: Massive Attack – Angel; Daft Punk – Doin’ It Right; Hans Zimmer – Why So Serious?

• OS: Taut sub‑bass extension with good slam; kick drum edges are neatly defined. Planars like Edition XS appreciate the current on tap.
• NOS: A shade rounder and bloomier, which can be very pleasing with dynamic headphones. Texture remains convincing, but the absolute tightest control is in OS.

Midrange

Tracks: Adele – Hello; Fleetwood Mac – Dreams; Agnes Obel – The Curse

• OS: Center image is locked; vocals sit forward without shout. Piano transients are clean and decay smoothly.
• NOS: Vocals sound a touch more corporeal, with a hint of sweetness to upper mids; guitars have a woodier timbre. It’s a very easy listen for long sessions.

Treble

Tracks: Norah Jones – Don’t Know Why; Vivaldi – Four Seasons (Carmignola); Tool – Pneuma

• OS: Airy and extended; cymbal sheen is crisp without edge. Microdetail retrieval is strong for the price.
• NOS: A bit softer on attack; hi‑hat tizz is reduced which many will welcome with brighter headphones/IEMs. Extension remains respectable.

Soundstage and Imaging

• OS: Stage is wide with stable left‑right placement and good center fill; depth layering is better than expected at this price.
• NOS: Perceived space grows a hair wider and more diffuse; macro‑images feel a little larger. Great for ambient, live, and orchestral.

Comparisons

FiiO K11 R2R

• Size and build: K13 R2R is noticeably larger than the K11/K11 R2R — keep desk space in mind.
• Power: K13 R2R’s balanced headphone output jumps to a rated 2400 mW into 32 Ω, which is a clear upgrade over K11 R2R for planars and high‑impedance dynamics.
• Features: Balanced inputs and linear PSU upgrade support make K13 R2R more flexible in a desktop chain. The companion app with 10‑band PEQ is a big quality‑of‑life win too.
• Sound: Both offer OS/NOS. K13 R2R sounds a touch more spacious and authoritative in OS, with better headroom; NOS remains that easy, organic R2R vibe. If desk space and budget allow, K13 R2R is the more future‑proof box.

For reference, see my K11 R2R review

K13 R2R vs K11 R2R — key specs at a glance

Specifications and Measurements

Core specifications

• Color: Black, Silver
• Main control chip (MCU): ESP32‑S3
• USB chip: XMOS XU316
• DAC: Fully differential true 24‑bit R2R DAC resistor arrays
• Volume control chip: NJW1195AV
• R2R and LPF op‑amp: OPA1642 ×4
• LO buffer op‑amp: LTA8092 ×2
• Headphone amplifier: OPA1642 ×2 + TPA6120A ×2
• USB input: 384 kHz/32‑bit, DSD256
• Coaxial input: 192 kHz/24‑bit, DSD64
• Optical input: 192 kHz/24‑bit
• USB connector: Dual Type‑C
• Display: Custom LCD
• Power input: AC 100–240 V 50/60 Hz; DC 12 V/2.5 A
• Dimensions: About 210 × 188 × 42 mm (including feet)
• Weight: About 980 g
• Frequency response: 20 Hz–80 kHz, attenuation < 2.9 dB
• SNR: ≥ 116 dB (A‑weighted)
• Noise floor: PO < 5 µV (A‑weighted, M gain); BAL < 8 µV (A‑weighted, M gain)
• Output impedance: PO < 0.7 Ω (32 Ω load); BAL < 1.5 Ω (32 Ω load)
• THD+N: About 0.0173% (1 kHz/−6 dB @ 32 Ω)

Detailed output performance (as provided by FiiO)

6.35 mm headphone output — High gain, OS mode

FiiO have lots of measurements for various configuration on their website but I thought i would provide some of the key metrics below:

4.4 mm balanced headphone output — High gain, OS mode

For me, the 2 key values are the 2.4mW into 32 Ohms )which is great and easily enough for the majority of headphones) and the THD+N of 0.0173% which is roughly 75 dB SINAD which is perfectly respectable for a R2R DAC. Objectively minded readers will note this is far below state‑of‑the‑art DS DACs — and that’s rather the point here: it’s the particular distribution of distortion and the resultant presentation that many R2R fans seek out.

XLR balanced line output — OS mode

An interesting (marketing) comparison

FiiO shared a comparison graphic focusing on harmonic structure. Take it with the usual grain of salt, but it’s illustrative of the point they’re making:

I’ve highlighted two aspects: (1) the focus on harmonic components around the fundamental, and (2) how some typical R2R implementations show more inter‑harmonic noise. FiiO’s message is that K13 R2R emphasizes the harmonics we tend to perceive musically, rather than minimizing total noise at all costs.

Rating explanation

• Pragmatic Rating (5/5): It does exactly what it promises — a feature‑complete, powerful, usable R2R desktop DAC/amp at an attainable price, with OS/NOS to allow people to pick their own flavour.
• Price (5/5): R2R at ~ $320 with these features and power is outstanding.
• Features (5/5): Balanced I/O, real power, app‑based 10‑band PEQ, remote, linear PSU option.
• Measurements (3/5): Objectively well short of DS benchmarks; subjectively, that’s the appeal for many.

Who is it for?

• Listeners who want to explore R2R without spending $1000+ and want something much more powerful than FiiO previous R2R the K11 R2R.
• Those who want to pick between OS accuracy and NOS character, track by track

If you already know you want just the most transparently accurate sound, want PEQ and similar Power, I feel you should get a different headphone DAC, for example, the Topping DX5 II which I recently reviewed but for those you are curious about R2R this is a great option.

Conclusion

FiiO is doing the hobby a service here. By bringing a thoughtfully implemented, fully balanced 24‑bit R2R DAC/amp to a mainstream price, they let more people decide for themselves whether they prefer OS accuracy or NOS character — without the usual R2R tax. The K13 R2R adds power, polish, and flexibility over the K11 R2R while keeping the clean, modern aesthetic that fits most desktops.

If you are curious about R2R, I can’t really find anything to complain about with the K13 R2R. It’s bigger and far more powerful than the K11 R2R, but some people might want the even more retro styling of the upcoming “Warmer R2R” DAC though that is just a pure DAC and doesn’t include nearly as many features as the K13 R2R.

So for those who want to experiment a little with a retro ‘sound’ but still want a powerful headphone output and all the modern features like PEQ, Balanced outputs, remote control, and a nice display, the K13 R2R is an easy recommendation.