FiiO K11 R2R DAC: Affordable R-2R desktop DAC & headphone amp. Let's talk about R-2R and euphonic preferences.

It has been more than a year since I last measured or reviewed a DAC!

To be honest, in 2026, DACs are IMO boring from the perspective of expecting any sonic progress when it comes to high-fidelity audio. They are very much a "solved problem" and will not pose any challenge for the audiophile who desires accuracy. Unless there's some new technology to evaluate or must-have features, digital-to-analogue conversion has clearly matured to allow extremely high resolution playback - perceptibly perfect even - within reach of basically everyone in the last decade.

[In the big cultural-level picture, I think we're at the phase now with less expensive products (eg. Chi-Fi) where more than adequate function has been achieved and we're going to be seeing an emphasis on "Design-Driven Innovation" where emotional, symbolic, and esthetic significance become more important with each generation for product differentiation. I think we're already seeing this with the FiiO line-up as I describe related products to this at the end of this post. In time, I suspect this will be an existential threat to many current High-End brands.]

Because of that lack of excitement around evaluating yet another DAC objectively, for more than 6 months now, this FiiO K11 R2R DAC (US$176, Canada link) has been sitting on my table for evaluation! 🙄 I bought this with the plan of using it in my office at the hospital for desktop speaker playback and headphone listening which I'll do after publishing this.

Make sure not to confuse this model with the slightly less expensive FiiO K11 non-R2R DAC (US$145) which uses the Cirrus Logic CS43198 chip. Feature-wise, I think they're very similar and look identical other than the stylized "R2R" stamped on the top of the case.

Okay, let's put this through its paces...

As you likely already know, R-2R refers to the digital-to-analogue conversion being done through a discrete resistor ladder built from two resistor values, one pair per data bit, rather than more modern techniques like sigma-delta modulation with its high frequency oversampled bit-stream that usually will achieve better linearity with less expense.

R-2R ladders are based on old technology (back to the '80s, reminiscent of stuff like the Philips TDA154x multibit chips) but are typically more expensive because precise resistor matching across each rung of the ladder must be maintained in order to achieve accuracy. This is particularly important for the more significant bits in the ladder since each level controls 50% of the full-scale output voltage. To frame the difficulty, to achieve full resolution, the circuit (not just individual resistors!) needs to be as accurate as the least significant bit. This means for 16-bit digital it has to be down to about 1/65,000 accurate and for 24-bits 1/16.7M accurate (realistically impossible). So, to keep a DAC at a competitive price point, compromises like the resistor precision will be sacrificed at some threshold for a classic passive resistor ladder design.

We've seen this sacrifice before. For example, the Cayin RU6 R-2R dongle measured in 2022 utilizes a total of 96 x 0.1% thin film resistors. While this FiiO model also uses 0.1% resistors, the internal differential design doubles the total number of resistors to 192. In principle, this could be a more accurate/resolving device than the Cayin by reducing common mode noise, suppressing even-order harmonics, and perhaps improving SNR - we'll see.

While the internal design is balanced, the only balanced output on this K11 R2R unit is the front 4.4mm headphone jack.

The headphone amplifier section is based on SGM8262-2 x 2 chips, rated as 460mW/ch into 32Ω at 1% THD+N through the single-ended 6.35mm output, spec'ed at <1Ω impedance. And up to 1.3W/ch into 32Ω at 1% THD+N through the balanced 4.4mm jack with <1.5Ω output impedance reported.

DAC dimensions: 5.25" x 5.25" x 1.25" approximately. Milled aluminum case, ~430g.

The K11 R2R sports only single-ended RCA outputs at the back for your desktop or sound room audio system. There's the power jack, USB-C, TosLink, and Coaxial S/PDIF digital inputs.

It accepts up to 24/192 through the S/PDIF Coax and TosLink inputs. I noticed the FiiO specs sheet says TosLink up to 24/96 only, but on my unit 192kHz works fine. The USB-C can handle a wider range of sample rates up to 24/384 and up to DSD256.

As a basic DAC, it's missing amenities you might see elsewhere like a remote control or Bluetooth playback. Here are the box contents including the 12V/2A power supply, a USB cable, 6.35mm to 3.5mm headphone adaptor, and basic but nicely printed "Quick Start Guide":

The default top "FIIO" translucent logo indicator lights up with a few colors when in use, corresponding to the sample rate (like Chord's products with their bulbous translucent buttons) - cyan ≤48kHz PCM, yellow >48kHz PCM, green DSD:

Yellow logo indicator, 96kHz sample rate.

There's a front LCD display that shows the details, mainly sample rate and volume level (99 = max volume), and which output is selected. Using the knurled push button knob, we can turn it ON/OFF by holding down for something like 5 seconds, double click to switch outputs (variable line preamp, 100% line out, headphone out), turn for volume control, hold down the button for 2 seconds and there's a menu system to change various options like screen/logo brightness, logo color selection +/- pulsation, UAC1/2 mode, and also whether you want standard oversampling (OS) or NOS mode.

In use, the case does get slightly warm, nothing to be concerned about and as I recall, it's less warm to the touch than what I remember of the Cayin RU6 in that small dongle form factor.

A look at the bottom of the unit. Rubberized base.

As I mentioned, this DAC has been sitting on my table for awhile already which probably meant that the firmware was out of date. Indeed, there's a M79 firmware which I downloaded and installed before all measurements and listening.

The interesting thing about this new firmware is that it adds 1-bit DSD decoding as per the discussion on the firmware page. Prior to this new firmware, the DSD data was always converted to PCM for playback. We'll take a look at this a bit later.

Okay guys and gals, let's run some measurements to see how it works and how accurate this DAC is.

I. Oscilloscope & Impulse Response

Let's stick the DAC's RCA output into a digital oscilloscope and have a look at 1kHz 0dBFS sine waves to see the maximum output level with the 2 channels overlaid:

That looks great from a channel balance perspective. A standard 2.8Vrms RCA line level output.

Through the menu, we can change it over to NOS mode to check out some stair-stepped waveforms:

Let's have a peek at the impulse response to see what kind of filtering they're applying when oversampling (8x oversampling based on what I've seen people mention online):

It's a typical steep linear phase filter with the usual pre-ringing and true NOS without interpolation. Compared to the Cayin RU6, the NOS impulse is properly temporally aligned, good to see.

So how steep is that filter? Let's see:

With a 44.1kHz signal, by Nyquist at 22.05kHz the signal is down -6dBFS and by 23kHz, it's down to -24dB. As you can see, there's quite a bit of ultrasonic energy in the NOS curve that's left unfiltered due to imaging artifacts from the zero-hold "stair-step".

II. RightMark Comparisons:

Let's see how this DAC scores compared to others that I have around here. To start, let's consider standard resolution 16/44.1 and compare it to the Cayin RU6 R2R dongle DAC with OS and NOS modes:

Clearly, we can see that at standard resolution 16/44.1, the FiiO K11 R2R is a more accurate DAC compared to the Cayin RU6 with dynamic range better than 90dB.

The frequency responses are almost exactly the same between the two. Response is flat with OS. As we've discussed years ago, turning off filtering will result in a frequency response that rolls off -3dB into 20kHz which is what we see with both R2R DACs.

Otherwise, the FiiO is capable of slightly lower noise, better crosstalk, and lower distortion as per the IMD+N sweep. As expected, the oversampling (OS) setting is able to achieve lower distortion for both units.

Obviously, these days with high performance devices, it's not how something measures with standard CD-resolution signals that separates the truly "high fidelity" DAC from those that aren't. Let's look at 24/96 performance and this time let's add an inexpensive chip-DAC into the mix, the old Topping D10s (based on ESS ES9038Q2M chip), and also let's compare with an example of a state-of-the-art resolution DAC - my Topping DX9 (based on the AKM AK4499EQ):

The first thing to notice is that the FiiO K11 R2R DAC is capable of low noise performance (below -110dB) which is something that the Cayin RU6 was not able to muster when fed 24-bit data. The Cayin is not a truly "hi-res" DAC.

However, look at the distortion figures (THD and IMD) of the K11 R2R compared to even the very inexpensive Topping D10s. This spread is a good example of what can be accomplished with more modern technology found inside a sigma-delta device compared to R-2R at this kind of price point.

With a bit more money, tapping the XLR output from the Topping DX9 DAC provides even better low-noise, low-distortion performance:

Notice the poor noise floor performance of the Cayin RU6. Thankfully, the FiiO K11 R2R has low noise level similar to Topping D10s.

After all these years, I still think the Topping D10s remains quite a remarkable and good-sounding little DAC. There's a clear gap in measured fidelity between the inexpensive R-2R DAC and the chip ΣΔ DACs.

III. A deeper looking into distortion - THD+N, stepped sine sweeps, Multi-Tone

As you can imagine, with that IMD+N sweep result for the K11 R2R, we're not looking at a DAC with very low distortion. Let's see what a 0dBFS 1kHz tone at 16/44.1 looks like captured through both channels; comparing oversampling (OS) and NOS modes:

While the noise floor is cleaner with oversampling turned on, the average THD+N however does not reflect a significant change as it's dominated by the high harmonics. Notice the ENOB (Effective Number of Bits) score - it means that this DAC playing a 16-bit 0dBFS 1kHz tone, with combined noise and distortion is equivalent to an 11.5-12-bit device.

Let's look at this as a THD vs. Output Level graph, 1kHz tone, 1dB steps from -120dBFS:

As we saw above with the 0dBFS 1kHz tone, the best THD(+N) hovers around the -70dB point. The third harmonic predominates until about -23dBFS, above which the 2nd harmonic is strongest.

We can see an interesting glitch distortion pattern every 6dB which corresponds to each bit transition of the resistor ladder. R-2R ladder DACs with subtle resistor mismatches can cause "differential nonlinearity" (DNL) errors worse at certain code transitions, for example going from 01111 → 10000 with multiple bits flipping simultaneously might create larger bumps on the THD vs. output level. (Notice that this is different from the ESS pre-Hyperstream IV modulator pattern discussed here.)

Let's now have a look at the output level linearity:

Again, this is not unexpected given the limitations we're seeing elsewhere. In comparison, a modern very high performance DAC like the Topping DX9 deviates by 0.5dB way down below -127dB and even a modern AV receiver like my Integra DRX-8.4's pre-outs using its internal DAC achieves -115dB before the same amount of deviation.

Now, instead of running the stepped sine across output levels, let's step across the audible frequencies to see if there's anything unexpected at 3 output levels (0, -9, -20dBFS):

Harmonic distortion remains pretty high and we see some noise level (N) fluctuations at the higher frequencies. However, the harmonic distortion amounts appear predictably flat.

Beyond looking at single-tone harmonic distortion, we can quickly look at a multitone test. Here's a Triple-Tone test (48/960/5472Hz) I've used over the years to add complexity. I think this is a better single-number measurement of DAC distortion than just 1kHz THD+N/SINAD as it spans a number of frequencies from the bass to higher treble and will stimulate intermodulation:

As you can see, the TD+N comes out to around -67dB. As a comparison, the Cayin RU6 DAC was only able to achieve -56dB for both its OS and NOS modes. With modern hi-res ΣΔ DACs, like even the inexpensive SMSL DO100 from a few years ago, TD+N is better than -110dB.

A complex multi-tone pattern might be able to unmask distortion better in R-2R DACs with DNL-related issues since single tones might be only of a fixed pattern representing a smaller set of resistor states.

IV. Jitter

Quickly, let's have a peek. When it comes to jitter, asynchronous USB is typically better than S/PDIF.

Hmmm, clearly not the cleanest J-test results. It looks like there are some data jitter sidebands in that 16-bit test, and a bit of spurious noise. As for the 24-bit J-Test, that's probably one of the most clear examples of random jitter causing a "skirt" at the base of the signal that I've seen in awhile.

Hopefully the S/PDIF isn't worse:

Looks almost identical. That's good I suppose. 😉

Although not pretty, I'm not particularly concerned about this amount of jitter being audible as all the anomalies are below -100dB from the signal peak and the J-Test exacerbates the effect more than what one would find with actual music playback anyways.

The whole concept of jitter as an audible, or worrisome concern is mostly just a bogeyman folks looking for an anti-"digital sound" have been dragging out for decades or using to justify, without evidence, why something supposedly sounds better than another to them.

DSD playback = green top color. Display shows specifically DSD128.

V. Quick look at DSD playback

As a R-2R multibit DAC, the K11 R2R is not really designed for DSD's multi-MHz 1-bit switching playback natively so the initial release firmware always took the 1-bit data and internally converted it to PCM through the FPGA; they call this the "D2P" mode.

Since firmware M79, the company has added a "1-Bit" decode mode implemented as a 24-tap FIR filter fed with the DSD data plus they mention another active low-pass filter applied to further remove ultrasonic noise.

One consequence of this mode is that the noise floor with 1-Bit decode is significantly higher. So, let's use my +3.1dBDSD 1kHz signals and compare what DSD64/128 and "D2P"/"1-Bit" decoding look like:

Using standard UAC2 Windows WASAPI driver playback, maximum DSD128. ENOB 12-13-bits.

Overall, the distortions remain high so there's not much difference in the THD+N at around -70dB. But clearly the 1-Bit mode (right) noise floor is substantially higher than D2P and the output level of the 1-Bit mode is about 5.5dB lower than conversion through PCM.

Regardless of what we do, to achieve good quality sound from 1-bit quantization requires a way to manage the noise so it's outside the audio band through noise-shaped integrator feedback, typically of multiple orders (high-order noise-shaping filter). As you can see, the ultrasonic noise is there with DSD playback whether through the DSD-to-PCM route or their 1-bit-FIR filter method. DSD128 pushing the noise further ultrasonic than DSD64.

Roon ARC playing via USB-C from Android phone to FiiO K11 R2R. AKG Q701 headphones. 49/99 on the volume control with high gain is plenty loud enough.

VI. Headphone output

Let's have a look at the unbalanced 6.35mm headphone output since this is all I'll be using at my office where this DAC will live.

First let's check the output impedance:

Notice frequency response drops quickly below 15Hz.

I'm doing the above sweep at High Gain, -3dBFS in 24/96. Notice the scale of the graph is just 3dB on the Y-axis so we're zooming into the output level to separate those curves. Blue is 75Ω load, Red is 20Ω load and as per previous measurements, I used my old Polk Ultrafit 2000 headphones as a test load of an actual headset with fluctuating impedance that dips down to 15Ω (previously measured and discussed):

The FiiO K11 R2R handled things quite well. Frequency response variation with the Ultrafit 2000 was around 0.3dB, nothing to worry about. Notice with NOS mode (dashed lines), we see earlier high-frequency roll-off as expected.

Using this data, we can estimate the 6.35mm single-ended headphone output impedance (at High Gain) to be around 1.3Ω. The specs officially say <1Ω.

Next, here are the THD vs. 1kHz output level stepped sine from -60dBFS with the device at High and Low gain settings into low impedance (20Ω) and moderate impedance (75Ω) loads, both channels driven:

I did not measure the Medium gain setting since it'll just be intermediate to those above and I'll forego the high impedance (560Ω) load that I've used in the past.

[For the record, measured maximum Vrms at the various gain levels on my unit: Hi = 3.97V, Med = 2.55V, Lo = 1.28V.]

The main thing we want to see is whether the headphone amp is able to provide adequate current into the low-impedance load. Indeed, this DAC/headphone amp has no problem providing enough current into 20Ω without clipping at maximum output which equates to about 800mW/ch.

For those who have very demanding headphones with low impedance and/or low sensitivity, use the balanced 4.4mm headphone out - this should get you another 4.5-6dB based on FiiO's data (I did not measure). It's good that these days many companies like FiiO already publish quite a bit of data such as this so I'll leave you to explore further.

I've used my AKG Q701's shown above as a benchmark being one of my less sensitive headphones. The K11 R2R's headphone amp was certainly loud enough through the 6.35mm output at high gain.

VII. Subjective sound quality

Ultimately the question is "How does this sound?", right?

I went back and had a look at the notes from my listening sessions with the Cayin RU6 in 2022. And also the follow-up post I made about audible distortions from that headphone DAC so I can revisit listening to some of the same songs with the same headphones.

Overall, my impression of this FiiO DAC/headphone amp is certainly better than what I thought about the Cayin RU6. Most importantly is that I could not hear the distortion on the "A Million Dreams" track from The Greatest Showman (2017) using the very detailed and unforgiving Sennheiser HD800 headphones.

Yeah, I guess there's a general subjective sense of enhanced "body" with this DAC likely thanks to the non-linear distortions. I would not say it's an extensive "bloom" though compared to some tube amps or vinyl, but I think it can add euphonic character to the sound quality. For example, Ella Fitzgerald sounded great on Pure Ella with really nice timbral details and midrange heft to her voice.

Likewise, The Modern Jazz Quarter's Blues At Carnegie Hall (1966) was rendered quite well through my modded Dekoni Blue headphones conveying the ambient sounds in a live venue. As an old analogue recording, the tape hiss on this album was easily heard and IMO can be a bit distracting with the intimacy of headphones, less so through loudspeakers.

I made sure to listen to other more modern stuff of course. For example the insanely intense "Techno Syndrome 2021" from the Mortal Kombat (DR8, 2021) soundtrack. I have no complaints about how well this DAC can deliver sub-bass content. As usual, when it comes to DACs capable of delivering flat frequency response from 20-20kHz, limitations to bass depth and realism are way more than likely due to the transducer, be it headphones or loudspeakers+room, than blaming the DAC. With a track like this, having subwoofer(s) that goes down to 20Hz is mandatory for the full experience. 😉

Beyond headphone listening, I plugged it into my main speaker system one evening and enjoyed Eva Cassidy's Live At Blues Alley (DR11, 1997). On songs like "People Get Ready", the soundstage was rendered nicely with Cassidy's voice anchored front-and-center, instruments demonstrating good positional depth, great "microdynamics" with instrument attacks on percussion and guitar with smooth decays, claps and other audience sounds come across clearly and detailed with unhindered dynamics. The K11 R2R rocks on tracks like The Offspring's "Staring At The Sun" from Americana (1998); no issues with complex, loud, compressed rock music.

For classical music lovers, Ayako Tahara's viola and Kaoru Jitsukawa's piano sounded fantastic on Arpeggione Sonata (DR13, available as DSD64, 2026). Deeply moving music, warm tonality, excellent technical depth! Check out the first track, Schubert's "Sonata for Arpeggione and Piano in A minor, D 821" for a taste. While we can see the elevated noise level on the K11 R2R 1-Bit decode setting above, at normal listening levels, this did not intrude into the enjoyment of the music when I listened to the DSD64 recording.

The effect of NOS mode to me is a subtle reduction in the extreme treble. A small amount of loss of "air" maybe - often not noticeable because not every song contains extended treble content >8kHz. Usually I prefer listening with OS but on occasion I believe NOS might be able to reduce some of the fatigue when listening to harsher-sounding compressed content or maybe older thin-sounding stuff - Culture Club's Kissing To Be Clever (1982) comes to mind, check out the sizzle in "Do You Really Want to Hurt Me". On high resolution DACs, the imaging distortions from NOS might create intermodulation anomalies in the audible band during playback. However, with this DAC, the intrinsic R-2R distortion is already likely at a higher level than intermodulation from ultrasonic imaging.

While I could go on, these are all just my subjective sighted impressions.

I invite you to listen for yourself using neutral playback gear. Here are my Archimago's Musical Performance Track (AMPT) recordings of the FiiO K11 R2R DAC in OS and NOS settings. 

FiiO K11 R2R DAC (OS) AMPT (174MB)

FiiO K11 R2R DAC (NOS) AMPT (205MB)

24/96 capture through RME ADI-2 Pro ADC

The OS file is smaller because ultrasonic distortions filtered out.

These were captured directly from the DAC to my RME ADI-2 Pro ADC in high-res 24/96 then trimmed slightly and volume level normalized. Listen for differences by using a high-resolution DAC and with high quality headphones rather than loudspeakers to avoid room effects. Also, feel free to use the Foobar ABX Comparator tool to test your Golden Ears against other devices - can you hear the difference? 😊

[As usual, my belief is that sighted listening discussions like this usually is meaningless because so much is just derived from our own psychological projections and limited echoic memory. Still, I guess such videos could be somewhat entertaining if one has nothing else to do.]

VIII. Summary

Well guys and gals, I know that there's plenty of "literature" out there talking about the magic of R-2R DACs - like this one from LAiV "What Is an R2R DAC?". While it's always exciting to think about different (not particularly new in this case) technology, I think we need to make sure to be sober in the face of advertising claims and subjective testimonies and contrast that with evidence of audible superiority. I do not believe that the article's claims of the benefits from a "more direct conversion path", the "more evenly distributed" noise floor, or claims of less listening fatigue have ever been proven to be actual advantages of R-2R technology.

Summary of the usual chatter online about R-2R vs. Sigma-Delta DACs.

As I said in my Cayin RU6 DAC review previously:

I'm happy to take the "minority report" and state that I don't particularly find multibit R-2R +/- NOS DACs that I've heard as being particularly "natural" or "real" sounding as some people seem to claim.

I remain of the same opinion when it comes to this specific FiiO DAC. For example, you can read and watch other reviews like this, this, this or this talking about how "special" the device is. For sure, as a DAC at this price point, there are many reasons to recommend this product. However, in terms of the sound quality, as you can see from the measurements above, there are indeed all kinds of differences between this DAC and modern hi-res devices that indicate a lower level of fidelity.

While I appreciate that the FiiO K11 R2R DAC has low noise (as per the RightMark 24-bit results compared to the Cayin RU6), the notable objective concern is that the amount of non-linear (ie. harmonic, intermodulation) distortion is high with this device. With a 0dBFS 1kHz THD+N between -70 to -73dB, triple-tone TD+N of -67dB, linearity deviating beyond 0.5dB by -80dB, and some pretty funky looking jitter tests, this is among some of the higher distorting DACs I've measured. In fact, a modern AV receiver like the Integra DRX-8.4's internal DAC achieves even better resolution.

There's no need to beat around the bush; R-2R DACs like this obviously can/will measure poorly by today's standards. Unless we're salesmen, there's no need to rationalize that these distortions are magically good, "more organic", "more direct", or anything like that to brush away the obviously reduced transparency. It's just that some listeners prefer a noisier, less linear system and interpret this sound as "organic" and other similarly euphemistic subjective descriptions.

I believe that an honest euphonophilic audiophile understands and embraces the fact that he prefers to listen to audio hardware colored to taste and accepts that the device isn't particularly "high-fidelity" or of "high-resolution" (which for a DAC can be defined as surpassing 16/44.1). The euphonophile seeks out devices that embodies a kind of character to the sound that resonates with what he/she desires - maybe even for some people, their choice of certain technologies becoming an external representation of their own character (ie. "Hey audiophiles, I'm Bob, the vinyl/LP-is-best guy!"). In that respect, an R-2R DAC like this may be similar to a tube amp, or vinyl playback with preferred technical imperfections. There is absolutely nothing wrong with this so long as we have insight into our preferences and don't say silly things like: "Vinyl is hi-res audio!" or "R-2R DAC's are the most accurate!". Obviously, factually wrong on both counts.

Having said this, when it comes to non-linear distortions, remember that a THD+N of -70dB is still just 0.03% and years ago, when we tested audibility of harmonic distortion, we saw that most human ears/brain are simply not highly sensitive. To me, this DAC sounds absolutely fine and you'll more than likely have a blast with your favourite music! It still measures significantly better than the Cayin RU6 with about 10dB lower TD+N on the complex Triple-Tone, and comparatively, I don't hear any bothersome anomalies.

At less than US$200, this is a great entry price into a discrete, FPGA-based, R-2R DAC with an interesting 1-bit DSD decoding option if you're looking for something away from the well-trodden experience of sigma-delta hi-res chip devices.

While I would not have any concerns with using this in a hi-fi loudspeaker system, the lack of amenities like a remote control means it's really targeted for desktop computer usage where within arm's reach you can switch between headphones and line out for powered loudspeakers which is exactly what I'll be using this for.

For completeness, I'll mention that FiiO has other R-2R DACs in their line-up including the upgraded FiiO K13 R2R (currently US$320) with more powerful headphone amp, internal switching power supply, balanced XLR output, parametric EQ and Bluetooth. The core R-2R DAC architecture is the same as this K11 R2R so THD+N would be similar even if the noise floor might be lower with balanced output. I see they've made a peek-a-boo top window so you can marvel at the R2R circuitry.

If you want even more analog "bloom", they have the retro-styled FiiO Warmer R2R (US$350) with internal linear toroidal transformer power supply, analog VU meter, and a tube buffer but no headphone amp. With tubes, it looks like you'd probably pay a price in resolution/fidelity with higher THD+N at something like -65dB; but I guess it's "warmer" - nothing wrong with that if that's what you desire. 😏

The FiiO's K17 R2R (below US$1000) is their more resolving, higher-end model with streaming end-point capabilities (including Roon Ready), touchscreen control, EQ, XLR line output, balanced XLR headphone out, upgraded clocks, linear power supply, up to 4W headphone power, WiFi, Bluetooth, ethernet, aluminum remote control, and a 'PRO' segmented architecture that improves the accuracy of the most significant 5-bits (top 30dB, solves DNL problem) with a thermometer-coded network (unary coding), paired with the resistor ladder for the lower bits. Specs suggest THD+N around -85dB; certainly quite good for discrete R-2R technology plus quite a lot of features, and the price is still within reach of most audiophiles.

I think the K17 R2R would work really well in a full-sized sound room system, allowing the audiophile to differentiate himself and talk about how he prefers the "R-2R sound", show off the neo-retro esthetics, and at the same time objectively achieve quite a well-measuring system to satisfy the quest for high-fidelity. If I were not such a multichannel listener, I'd probably get one of these for my room!

Realize though that as we achieve higher resolution R-2R, do not be surprised if it sounds more and more like a good, clean sounding, sigma-delta DAC - but you pay a higher price because it's harder to achieve! In the same way, if you're a DSD listener, as you improve the resolution jumping from DSD64 to DSD128 to DSD256 - each time pushing the noise further from the audible spectrum - the measured and IMO subjective impression ends up being what sounds like cleanly reproduced PCM 24/96 and above. The "magic" was always in the measurable imperfections even if companies and reviewers might not want to acknowledge, or even celebrate that fact.

[As I suggested at the beginning, notice the product differentiation FiiO is doing here as it expands the line-up beyond the generic box and embraces things like symbolic significance with esthetic retro styling (wood panels, analog UV meter, classic-looking knobs), not pushing technical qualities as much. Per earlier, the core DAC function is a "solved problem" that's unlikely to be a strong differentiator for many music lovers.]

In the last few years, there has been an expansion of R-2R DAC options from the likes of Denafrips, Schiit, Holo Audio, LAiV, Musician, SMSL, Gustard, Topping, HiFiMan, etc. Lots to choose from at various price points.

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Warning: This next part is about an unofficial firmware hack. Doing it would likely null your warranty and might even brick your DAC if done incorrectly. Proceed only if you're comfortable doing this stuff.

If you have a FiiO K11 R2R and find it annoying that the front knob double-click cycles through the 3 output settings of 100% fixed-volume line out, volume-controlled line out, and headphones, but would rather just flip between last-used variable line out and headphone volumes, here's an interesting firmware hack to try:

FiiO K11 R2R PO ↔ PRE Custom Firmware

I've gone ahead and installed this and it works well. If I really want to have the RCA line-out fixed to 100%, the menu setting is still there for "LO". If you're doing this, make sure to double check the SHA-256 hash to make sure it's exactly correct before updating with the custom firmware.

Say goodbye to the risk of sudden loud 100% volume when flipping between the outputs! It would have been great if FiiO just made this a menu option for either 3-way or 2-way output double-click switching in the firmware.

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Some music to end - here's Chance The Rapper with Death Cab for Cutie's "Do You Remember" from The Big Day (DR7, 2019). A sweet sentimental song.

Perhaps like the sentiments wrapped up in the idea of R-2R technology being older and therefore more "analogue" sounding? (Even if it has always been just a little more noise and subtly audible distortions. 😉)

Hope you're enjoying the music and keepin' it real, audiophiles. Cheers!