FiiO K17 R2R: R2R Done Right

 

FiiO's K-series desktop stack has always had a very clear job: sit on your desk, look the part, and drive basically anything you throw at it. The K17 R2R is the newest member of that family, and it takes the existing K17 chassis and swaps out the AKM Delta-Sigma setup for FiiO's own 24+5-bit segmented R2R PRO resistor array. Priced at $989.99, it isn't cheap, but it is meant to be the "do everything" desktop centerpiece for people who want a streamer, a DAC, and a proper amp section in one box.

I've had the K17 R2R on my desk for a good while now, alongside my existing K17 R2R that's already part of my regular rotation, so this review comes from genuinely extended use rather than a quick once-over.

Packaging and Build

The unit comes in a foam-padded box, well protected for transit. Inside you get an infrared remote control, a spare fuse, two USB-A to USB-C cables, a 6.35mm to 3.5mm adapter, and a dust cover for the front XLR port. FiiO doesn't bundle a USB-C to USB-C cable, so if you're feeding it from a phone or a modern laptop, you'll need to source your own.

Build quality is where the K17 R2R really shows its hand. FiiO kept the same layout as the original K17: the 3.93-inch bezel-less touchscreen, the multi-function knob, the LED ring, the small red power indicator. But this time around, real wood side panels flank the chassis, and to my ears the whole thing looks and feels noticeably more special than the original. It's a proper retro-modern desk piece, not just a slab of bent metal with a screen bolted on.

Connectivity is comprehensive. Up front you get 6.35mm, 4.4mm balanced, and 4-pin XLR balanced headphone outputs plus a USB-C port for quick hookups. Around the back there's coaxial and optical in/out, RCA and balanced XLR line outs, a ground-loop lift switch, a USB-B port, an RJ45 LAN socket, and a wireless antenna connector. It also runs Roon Ready, Apple AirPlay, and can pull local files straight off a USB drive or a NAS over SMB/NFS, so it genuinely works as a standalone source if you don't want to boot up a computer.

Streaming and Local Playback
I actually put both of these to proper use rather than just leaving them as spec sheet bullet points. On AirPlay, streaming from my phone across the room, I didn't get a single connection dropout throughout my testing period, which is more than I can say for some other streaming-capable DACs I've had on my desk before.

For local playback, I hooked the K17 R2R up to my NAS through FiiO's app and streamed a mix of FLAC and DSD files straight off it. Both formats played back without a hitch, no stuttering, no dropouts, no fumbling around with the app to get it to see the NAS properly. I also pointed it at a shared folder on my Windows PC over the network, and it connected without any fuss, browsing and playing files directly off the shared drive just as easily as it did with the NAS. It's genuinely convenient to just pull up the app, pick an album, and have it play without needing a laptop or phone connected the entire time.

Features/Specification

• DAC: FiiO proprietary 24+5-bit segmented R2R PRO resistor array

• USB Interface: XMOS XU316, up to 32-bit/768kHz PCM, native DSD256

• Amplification: Fully discrete Class AB, ON Semiconductor MJE243/MJE253 transistors

• Power Output: 4000mW + 4000mW balanced into 32Ω, 1850mW + 1850mW single-ended

• THD+N: <0.0052%, SNR: ≥125dB, Noise Floor: <2.6μV

• Display: 3.93-inch bezel-less touchscreen

• Connectivity: Bluetooth 5.1 (Qualcomm QCC5125, LDAC/aptX Adaptive/aptX HD), Wi-Fi, Ethernet, Roon Ready, AirPlay, SMB/NFS NAS playback

• I/O: 6.35mm, 4.4mm balanced, 4-pin XLR headphone outs, RCA and XLR line in/out, coaxial and optical digital in/out, ground-loop lift switch

• EQ: 31-band lossless PEQ, 64-bit floating point DSP, Auto EQ headphone matching

Gears Used for This Review

• Aune S9C Pro

• FiiO K17 R2R

• Yanyin Baker

• Spirit Torino Twin Pulse IEM

• Fiio/JadeAudio JT9

Foreword

My review is solely based on what I hear via my equipment and I never consider my reviews to be objective in any way rather a subjective approach. Do take into consideration that everyone's ear anatomy is not the same, so the psychoacoustics perception might be different as well, but i believe it will not stray too far.

Sound Impression

The K17 R2R was given approximately 60-70 hours on my burn-in rig before any serious listening. Out of the box the treble had a slightly grainy edge to it, and over the first 20 hours or so that settled into something noticeably smoother, with the bass also becoming a touch more controlled by the end of the run.

Once settled, the character of this thing is obvious within the first few minutes. FiiO's 24+5-bit segmented R2R PRO ladder trades the sharper, more analytical presentation of the original AKM-based K17 for something warmer, more full-bodied, and to my ears, considerably easier to listen to over long sessions. It isn't a dark or rolled-off sound, it's more that everything has a bit of extra weight and a tinge of analog warmth running through it. Switching between NOS and OS mode gives you two flavors of that same character: NOS leans smoother and more relaxed, OS tightens up the transients and pulls out a bit more micro-detail. Both are useful depending on what I'm feeding it.

Pairing with FiiO JT9

• The JT9 is a planar magnetic headphone, and planars generally reward a source with authority and control, which the K17 R2R has in spades.

• On NOS mode, the pairing takes some of the JT9's naturally quick, slightly clinical planar attack and rounds it off just enough to feel less monitor-like without losing the driver's speed.

• Bass on the JT9 through the K17 R2R goes noticeably deeper and doesn't bleed into the mids at all, staying textured and controlled even during the low string intro on Behemoth's "Blow Your Trumpets, Gabriel."

• Vocals through this pairing sit a few steps in front of me, with good body and none of the planar sheen that can sometimes creep in on lesser sources.

• Soundstage opens up considerably. That hall like effect the JT9 is capable of on its own becomes even more convincing with the extra power and current on tap here, particularly on King Crimson's "People."

• Switching to OS mode and high gain adds extra sparkle and separation to cymbals and strings, which suits Tuomas Holopainen's "A Lifetime of Adventure" nicely, though I found NOS the better long-term listen for the JT9's already slightly airy treble.

Pairing with Yanyin Baker

• The Baker is an 8-driver hybrid, six balanced armatures plus two planar drivers, at 8Ω and 104dB sensitivity, so it's about as easy to drive as IEMs get.

• This is exactly the scenario the K17 R2R's own notes on synergy warned about: low impedance, highly sensitive IEMs don't let this amp flex the way higher impedance gear does.

• On low gain the K17 R2R is dead quiet, pitch black background, no hiss detected even with the Baker's planar drivers sitting right up against the noise floor.

• Tonally the R2R warmth still comes through nicely on the Baker's midrange, giving male vocals a bit more chesty weight than I remember from more neutral sources, and Zhao Peng's lower register benefits from that extra body.

• Bass stays fast and doesn't bleed into the mids at all, the planar low end on the Baker keeps its speed while gaining a touch more physicality from the K17 R2R's current delivery.

• It's a good pairing, just not the most exciting one. An entry level or mid range dongle will honestly get you 80% of the way there with the Baker; the K17 R2R's strengths are more obvious on harder to drive gear.

Pairing with Spirit Torino Twin Pulse IEM

• The Twin Pulse runs a dual 10mm beryllium isobaric dynamic driver setup at 16Ω and 114dB, and while the sensitivity number looks high, it's actually not fussy about hiss or background noise, so it plays nicer with a full-size desktop amp than the spec sheet alone suggests.

• This is where the K17 R2R's tonality really clicks. The Twin Pulse already has a smooth, musical signature, and the R2R's added richness complements that beautifully rather than piling warmth on warmth to the point of mush.

• Sub-bass on Juno Reactor's "Navras" has real weight and momentum through this pairing, with the isobaric driver's speed keeping things from turning into a single bass blob.

• Female vocals, tested with Faye Wong, come through with excellent texture and a natural sense of scale, out of head rather than boxed in, which is impressive for an IEM.

• Male vocals get that same chesty weight I noticed with the Baker, but with more nuance and layering behind it thanks to the Twin Pulse's higher technical ceiling.

• This is, to my ears, the best sounding pairing of the three tested here. The extra headroom and current from the K17 R2R lets the Twin Pulse's isobaric drivers stretch out fully, something a smaller dongle or entry level amp simply can't replicate.

Comparison: FiiO K17 R2R vs Aune S9C Pro

Both of these sit in similar price territory, the S9C Pro at $699 and the K17 R2R at $989.99, though the Aune is the more compact all-in-one, while the FiiO is the bigger, more feature-loaded desktop centerpiece with streaming built in.

Build-wise, the S9C Pro is the more understated of the two, a clean rounded chassis with a dual ESS ES9068 Delta-Sigma DAC setup, Twin JFET output stage, and PLL clock sync tech, capable of up to 5W balanced. The K17 R2R takes a completely different design direction, retro-styled with real wood panels and a touchscreen, and it also does a lot more outside of pure amplification, with the network streaming and local playback features the S9C Pro simply doesn't have.

Sound is where the two diverge the most. The S9C Pro, being Delta-Sigma, is the more vivid, direct, and dynamic of the pair, closer to a modern reference sound with punchy, well-controlled bass and a slightly more forward, energetic presentation. The K17 R2R runs circle around it in terms of timbre and organic warmth, the R2R ladder giving vocals more body and the overall presentation a more analog, holographic feel, particularly noticeable on jazz and vocal-heavy tracks. But in outright technical precision, transient snap, and that pitch black, ruler-flat neutrality, the S9C Pro edges ahead.

Driveability is close, both have plenty of power for the vast majority of headphones and IEMs, though the S9C Pro's slightly higher balanced output gives it a small edge with genuinely hard to drive planars.

If you want a source that streams your entire library without touching a computer and prioritizes a rich, musical, long-listening-session tonality, I would personally go for the K17 R2R. If your priority is a more neutral, precise reference sound in a smaller footprint and you don't need the streaming features, the S9C Pro is the better choice.

Final Thoughts

The K17 R2R is one of those products that's easy to recommend without much hesitation once you know what you're looking for. It isn't chasing measurement charts or trying to be the most neutral box on the market, it's chasing a specific, deliberately musical character, and it delivers that character convincingly across headphones, planars, and IEMs alike, provided the IEM in question has enough impedance to make the amp section work for its dinner. The wood panels aren't just decoration either, they genuinely elevate how the unit feels sitting on a desk day to day. Between the streaming, the local playback, the PEQ, and that R2R timbre, this has quickly become one of the more used pieces of gear on my desk. Recommended? Yes! Definitely!

The FiiO K17 R2R was sent over by FiiO for the purpose of this review. Big thanks to the FiiO team for the support and opportunity as always.

Head over to their store if you are interested in getting one:
K17 R2R Product Page

Fiio K17 R2R Aliexpress Store Link