FIIO K11 R2R

The K11 is FiiO's most compact and budget friendly all-in-one desktop DAC and headphone amplifier. A device that uses a single CS43198 DAC chip and dual SGM8262 amplifier op-amps for a fully balanced headphone output. So what exactly is the FiiO K11 R2R?



The FiiO K11 R2R is the exact same device as the K11 with one major difference. This is the first DAC ever made by FiiO to use a discrete, fully differential true 24-bit resistor array to do the decoding instead of delta sigma D/A converter.

Technical highlights

The FiiO K11 R2R features a newly developed four-channel fully differential 24-bit R2R resistor array that consists of 48 resistors per channel. A total of 192 high-precision ultra-thin film resistors with 0.1% accuracy and low-temperature drift between the four channels. The use of fully differential architecture results in lower noise with less FFT harmonics in comparison to a typical one.

The amp section of the FiiO K11 R2R is the same as in the K11 with dual OPA1642 op-amps to handle low-pass filtering and dual SGM8262 operational amplifiers to do the headphone amplification. What is not the same is the NJW1195A digital volume chipset for precise volume adjustment with low distortion between the two channels.

The device supports 24bit/384kHz PCM and DSD256 decoding in contrast to the FiiO K11 which supports 32bit/384kHz PCM and native DSD256 decoding.

You can read more about the FiiO K11 R2R here.

https://www.fiio.com/k11r2r



Dual operating NOS and OS modes

The K11 R2R employs dual operating modes. The NOS mode maintains the original sampling rate without any further signal processing while the OS mode oversamples all input signals to 384kHz. As we are going to discover later on, the NOS mode results in a more musical presentation while the OS mode delivers better technicalities and more clarity.

Connectivity

The FiiO K11 R2R has the same digital inputs and analog outputs as the original model. A well equipped device despite its compact size that features USB type-C, coaxial and optical digital inputs, plus RCA line out and two headphone outputs (6.35mm and 4.4mm). The line output can be set as fixed or variable for driving active monitors such as the FiiO SP3. The USB input supports OTG function for connecting to a smartphone while a USB to coaxial output bridge is also available.

Non Audio stuff

The FiiO K11 R2R has the exact same appearance as the K11 and the only way to tell them apart is the “R2R” logo that is engraved in white letters at the top part of the unit. The slim and compact sized chassis (147x133x32.3 mm), that can fit virtually everywhere, is made from CNC machined aluminum and is available in black and silver finishes plus a red one that is exclusive to the R2R model. Build quality and finish are simply exceptional far surpassing what is expected for the category.

Just like the K11, the R2R edition features a high contrast LCD screen that displays useful information and allows easy access to the configuration menu. The top of the chassis integrates a FiiO logo RGB light that will display different colors according to the input sampling rate. The bottom has a silicone anti-slip pad that prevents accidental move of the unit.



Operating the device

The device is operated with the aid of a single multifunction knob that allows the user to adjust the volume, select the desired input and navigate through the configuration menu. The operation is pretty simple and you can master it in a short time without even reading the manual.

Available actions include to select gain level, set the line output as fixed or variable, switch between NOS and OS modes, set LCD brightness and timeout, set RGB light brightness and pulsing status etc. You can switch between LO and PO on the fly by double-pressing the multifunction button. The unit will remember the last volume setting for LO and PO independently so there is no need to readjust the volume every time you switch modes.

If there is something to complain about is that there is no dedicated gain button and you can't switch between NOS and OS on the fly. A remote control and Bluetooth connectivity would be handy features but I guess that I am asking too much for the price.

Accessories

The package includes an external power adapter, a USB data cable and a 6.35mm adapter plus a quick start manual.



Power talk

The maximum power output of the FiiO K11 R2R is 1300mW/32Ω, slightly lower from the 1400mW/32Ω of the original model. Still powerful enough to run a great variety of full sized headphones, like the FiiO FT5, and at the same time silent enough for use with sensitive earphones. The noise floor is somewhat higher than the K11 but this is something that gets noticeable only with very sensitive earphones.

The FiiO K11 R2R features three gain settings each one with its own independent volume curve that is specially configured for use with different loads. So you always have the perfect volume adjustment no matter if you are going to use very sensitive earphones or more demanding over-ear headphones.



Audio stuff

So, what’s all the fuss about this R2R resistor array DAC? Does it make the FiiO K11 R2R to sound different from the original model or is it some kind of marketing trick?

Of course not, the FiiO K11 R2R does have its own unique sound character that is quite different from the original model. People familiar with R2R designs will know that they tend to sound more natural and realistic than most D/S implementations of the same category. An audio engineer must spend great effort to fine tune a D/S DAC in order to make it sound as natural as similar R2R implementations, and even then the latter will always have the edge in emotion or what we call musicality.

The original FiiO K11 is known for its great neutrality, it has an uncolored, crystal clear and transparent audio profile with exceptional fidelity for the category and at the same time it doesn't sound clinical or sterile. The K11 R2R happily sacrifices a tiny amount of fidelity and transparency for a considerably more musical and organic sound presentation.

The most audible difference is the complete absence of digital artificiality especially in the higher frequencies where the original model has the tendency to introduce some digital glare and artifacts. The treble is smoother and mildly forgiving, more relaxed but without lacking in extension and energy. Detail retrieval and resolution are also stellar while the overall technical performance is competitive, however the sound is presented in a different kind of manner where technicalities are pushed back in favor of a more holistic and sentimental approach.

The K11 R2R produces a natural and realistic timbre especially when you are listening to vocalists and the instruments of the symphony orchestra where it is able to recreate a very colorful and varied harmonic palette.

The sound of the K11 R2R reminds more of an analog set-up rather than the typical entry level D/A converter that is usually achromatic without having a character of its own. It is not that the K11 R2R will introduce sound coloration or it is lacking in fidelity but it does have the means to reconstruct the real essence of the music.

This kind of different sonic approach between the K11 and the R2R gets clearly audible in the low-end where the former presents a firmer and more controlled bass with deeper layering and clarity but the R2R version sounds fuller and more visceral with wider dynamic contrasts. The bass of the R2R has more meat around the bones, it is weighty and rounded while it possesses a very natural reverb.

When it comes to music matching, people who listen to electronic or similar stuff might prefer the advanced technicalities of the K11 but others who value musicality and timbre realism are going to love the R2R. Additionally, the K11 is going to pair better with warmer and slower headphones while the R2R can smooth brighter headphones like some HIFIMAN models.

All R2R DACs that I have reviewed so far have the tendency to outperform their D/S siblings when it comes to soundstage dimensions and the FiiO K11 R2R is not an exception despite being an entry level model. The K11 R2R not only surpasses the K11 but it is also much better than most other D/S DACs of the same category. And by writing “better” I mean that it presents a soundstage that is both wider and deeper than most D/S competitors, with far increased holography and deeper immersion into the recording venue. Everything feels more natural and realistic as the K11 R2R excels in time and space communication.



OS and NOS differences

The OS mode adds extra spice, more transparency and clarity to the sound, the presentation is more technical compared to the NOS, so it bridges the gap between the R2R and the OG versions of FiiO's K11. Still the K11 (and similar D/S DACs) has the edge in technicalities and fidelity, it is livelier and more energetic than the R2R. Additionally the OS mode introduces some kind of sharpness to the treble of the FiiO K11 R2R and robs its musicality. Still this is a nice option to have as it adds versatility and allows for better matching with various headphones and music types.

Line vs headphone output

The headphone amplifier of the K11 R2R is somewhat limiting the performance by killing the unique sound characteristics of the DAC which deserves a better amplifier. It is not that you are not going to enjoy its unique sonic features straight out from the headphone output but you must use the line output in order to truly appreciate what the R2R DAC is capable of doing. The embedded amplifier adds a bit of sterility, it doesn't allow the musicality to come forth, it limits the holographic properties of the soundstage and makes the timbre less natural.

I have paired the FiiO K11 R2R with the Schiit Audio Vali 2+ and I was blown away by the combination. For less than $500, this is a headphone system that sounds incredibly musical and organic with amazing timbre realism and tonal accuracy. So, don't hesitate to buy the FiiO K11 R2R as an all-in-one unit but then invest in a high quality external headphone amplifier (or active monitors) to unleash its full potential.



Conclusion

Right now the FiiO K11 R2R is the most cost effective option in the market for those interested in experiencing the immensely analog and organic timbre of an R2R DAC.

The headphone output might be holding the performance a little back but the line output is truly exceptional. I can only think of a couple of D/S DACs (up to a certain price point) that can match the lifelike and effortless sound presentation of the FiiO K11 R2R but they do have some digital glare issues that the latter doesn't have.

Honestly, this is the most analog and natural sounding DAC FiiO has made so far. I think that it is released to check interest and market reaction when it comes to R2R DAC designs. After finishing this review I am confident that it is going to be a huge success and sell like hot cakes, hopefully encouraging FiiO to design a flagship R2R DAC in the near future. Till then the FiiO K11 R2R is the most affordable R2R DAC ever made with a value that is hard to beat.

The review sample was kindly provided free of charge in exchange for an honest review. The price of the FiiO K11 R2R is $169.99 and you can buy it from here.

Technical Specifications

K11 R2R:

DAC: Fully differential true 24-bit R2R resistor arrays

Volume Control Chip: NJW1195A

USB Input Decoding: Up to 384kHz/32bit, DSD256

Coaxial Input Decoding: Up to 192kHz/24bit

Power Output (Single-Ended): Up to 460mW+460mW at 32Ω

Power Output (Balanced): Up to 1300mW+1300mW at 32Ω

Output Impedance: PO <1Ω (32Ω load), BAL <1.5Ω (32Ω load)

Weight: About 420g

Menu Features:

• SAM (Sampling): Over sampling (OS), Non over sampling (NOS)

• UAC: UAC 1.0, UAC 2.0

• LCD-B (Brightness): 1-3 brightness levels

• LCD-T (Screen timeout): 1/2/5/10/30 and 0 which means always on.

• RGB-M (Colors): 0/1/2/3/4/5/6/7/8 (Follow the audio/Red/Blue/Cyan/Purple/Yellow/White/Green/Or cycle all colors.

• RGB-P: Gives the option for the light to pulse or be constant.

• RGB-B (Brightness): 0(Off)/1/2/3/4/5

• IDLE (Smart Idle): On or Off

• UPDATE: Gives the option for a firmware update.

• RESET: Gives the option to factory reset all the settings.

• FW: Shows the firmware version.

Whats in the box:



If you’ve been swimming in the DAC world for a while, you’ll know not all digital-to-analog converters are created equal. Some are like your trusty Toyota sedan—reliable, efficient, but not exactly thrilling. Then there’s the FiiO K11 R2R DAC amplifier, which feels more like slipping into a classic car that’s been restored to perfection. It's not just about getting from A to B; it's about the ride.

The R2R Heart: An Old-School Approach with Modern Charm

At the heart of the K11 is an R2R DAC, using a trusty resistor ladder to convert digital signals into that warm, analog goodness we all crave. It's an older design, but much like vinyl records and retro sneakers, it's making a big comeback. Unlike the more common Delta Sigma DACs, which take their sweet time stepping through voltages, the R2R DAC just goes, "Nah, I got this," and hits the right voltage immediately. The result? A cleaner, quieter background between notes that feels almost like a deep breath between sips of good single origin coffee.

When I ran it through some of my favorite tracks, the difference was undeniable. Those quiet pauses? Dead silent. Like, ‘I-can-hear-the-neighbors-watching-TV’ level silent. The only time I noticed any noise was with super-sensitive IEMs, but even then, it was more like a faint whisper at the back of a concert hall—nothing that ruined the experience.




Sound Profile: Warmth, Detail, and That Cozy Blanket Feeling

The moment I hit play, the K11 greeted me like an old friend—warm, inviting, and with just enough detail to keep things interesting. The bass is full-bodied but never overbearing. There’s punch and impact, but it knows when to take a step back and let the mids and highs shine.

Now, the midrange is where the magic really happens. It’s the type of sound that makes vocals and acoustic instruments feel intimate and alive. Whether I was listening to some smooth jazz or a folksy singer-songwriter, the K11 kept everything distinct and free of clutter.

As for the highs, if you’re someone who finds sharp treble to be the equivalent of nails on a chalkboard, the K11 is going to feel like a cozy blanket. It’s detailed, but in a smooth, buttery way that makes long listening sessions a breeze. No ear fatigue here—just pure, laid-back enjoyment.

NOS vs. OS Modes: Two Flavors, No Wrong Answer

The K11 comes with a cool feature that lets you toggle between Non-Over-Sampling (NOS) and Over-Sampling (OS) modes, and it's a bit like choosing between a hot cup of tea or a strong espresso and if you know me i am an espresso guy In NOS mode, the K11 leans even further into that warm, analog-like sound. It’s laid-back, smooth, and perfect for when you just want to unwind after a long day. Think of it as a Sunday drive down a scenic road.

Switch it to OS mode, and things get sharper, more focused. The sound tightens up, bringing more clarity to the mids and highs. It’s like flipping on a high-beam—everything just becomes a little more vivid. Personally, OS mode was my go-to for most of my testing. It gave me that perfect balance of warmth and detail without veering too far in either direction.



Power Play: Handling Everything from IEMs to Hungry Headphones

Now, let’s talk power. One of the K11’s strong suits is its versatility. With three gain settings—low, medium, and high—you can easily adjust the output to suit whatever you're plugging in.

Low gain works well with sensitive IEMs, though I did notice a touch of distortion on some lower impedance models (likely due to the higher output impedance). It’s not enough to send you running for the hills, but worth mentioning.

Medium gain hits the sweet spot for most moderately demanding headphones, giving them enough juice to perform beautifully without pushing too hard.

Then there’s high gain. This is where the K11 flexes its muscles. Even with power-hungry headphones like my HiFiMan cans, the K11 performed flawlessly, barely breaking a sweat at mid volume. The dynamics were punchy, the headroom was expansive, and the sound had an authority that made everything feel effortlessly rich.




Pairing my Xduoo MH-02 with the FIIO K11 R2R.

Pairing the Xduoo MH-02 tube amp with the FiiO K11 R2R DAC amp creates an intriguing fusion of analog warmth and digital precision. Both devices bring distinct characteristics to the table, and when combined, they produce a sound signature that blends the best of both worlds.

As someone who enjoys experimenting with different audio gear pairings, the Xduoo MH-02 tube amp and FiiO K11 R2R DAC combo immediately piqued my interest. The K11's R2R DAC offers a natural and detailed sound with its resistor ladder architecture, while the Xduoo MH-02 tube amp adds a distinct analog warmth that is difficult to replicate with solid-state amplification.

When I first connected the K11 to the MH-02, I was curious to see how the pairing would affect the overall tonal balance. The K11 on its own already has a slightly warmer, more organic sound compared to typical Delta-Sigma DACs, and I wondered if the tube amp might overdo the warmth or cloud the details. However, I was pleasantly surprised by how complementary they were.



Sound Signature:

The most noticeable change when adding the Xduoo MH-02 tube amp to the chain is a fuller, more rounded presentation, particularly in the midrange. The K11 R2R DAC already has great resolution and separation, but with the MH-02, there’s a smoother, almost liquid-like quality to the mids and highs. Vocals, in particular, benefit from this pairing—there’s a richness and texture to voices that feels incredibly lifelike. It’s as if the sound opens up, giving more room for instruments and vocals to breathe.

The low end also gets a touch more body with the MH-02. The K11's bass, which is tight and controlled, gains a subtle bloom and warmth without becoming overly bloated. Bass guitars and drums sound deeper and more immersive, adding a bit more weight to the overall presentation. However, the pairing maintains excellent bass control—there’s no sense of sloppiness or excessive bleed into the mids.

What’s especially impressive is that the MH-02 doesn’t sacrifice the K11’s detail retrieval. Tube amps can sometimes introduce too much softness or blur finer details, but the MH-02 strikes a great balance here. The K11’s analytical side still shines through, offering plenty of micro-details and texture in the treble. Instruments like violins, cymbals, and pianos maintain their clarity, but with an added layer of richness from the tubes.

Dynamics and Soundstage:

One of the standout characteristics of this pairing is the enhanced sense of dynamics. The K11 is already good at delivering dynamic swings, but the MH-02 seems to add a touch more punch and energy, especially during crescendos or more complex passages. It brings a sense of musicality to the K11’s analytical precision, making for a more engaging and lively listening experience.

The soundstage also benefits from this pairing. With just the K11, the soundstage is well-defined but not overly expansive. Once the MH-02 comes into play, the soundstage feels more three-dimensional. Instruments and vocals have a greater sense of depth, and there’s more air between them. The result is a more immersive, enveloping soundstage that makes you feel like you’re in the room with the performers.

Build and Usability:

In terms of usability, this setup is relatively straightforward. Both the Xduoo MH-02 and FiiO K11 are compact, desktop-friendly devices, and they complement each other well in terms of design. The K11’s LCD screen is a nice touch, offering quick access to various settings, while the MH-02’s tube glow adds a visual warmth that complements its sonic character.

The MH-02 has ample power to drive most headphones, and when paired with the K11’s flexible gain settings, it’s easy to find the right balance for both sensitive IEMs and power-hungry over-ears. Whether you're switching between high-gain for a planar headphone or low-gain for delicate in-ears, the combination feels versatile and well-rounded.



Final Thoughts on my special combo meal:

Pairing the Xduoo MH-02 tube amp with the FiiO K11 R2R DAC amp creates a sonic experience that feels warm, immersive, and highly detailed. The K11’s R2R DAC brings an incredible sense of precision and detail, while the MH-02 adds that coveted tube warmth without sacrificing clarity or dynamics.

This combination works especially well for listeners who crave a more analog-like sound without losing the technical precision of digital audio. Whether you’re listening to jazz, classical, or acoustic tracks, the pairing brings out the best in both devices, creating a sound that feels both engaging and musical.

If you’re looking to enhance the natural warmth and organic detail of the FiiO K11, adding the Xduoo MH-02 tube amp into the mix is a fantastic way to take your listening experience to the next level.



FiiO K11 R2R—A Warm Hug for Your Ears

The FiiO K11 R2R DAC amplifier is like that friend who always knows how to keep things cozy and laid-back, but still manages to impress you with their hidden depth. Its warm and natural sound is a refreshing change of pace from the overly clinical, precise world of Delta-Sigma DACs. Sure, it may not be the last word in razor-sharp detail or surgical precision, but that’s not the point—it’s here to make music feel human again.

With its rich, textured presentation, the K11 delivers a listening experience that’s as inviting as your favorite comfy chair. Whether you’re in it for a late-night jazz session or just unwinding with your favorite playlist, the K11 has your back, ensuring those long listening sessions stay fatigue-free. It’s not just about hearing your music; it’s about feeling it—and the K11 excels at that.

Is it perfect? Maybe not for those chasing the most analytical sound out there. But for anyone who values warmth, musicality, and a touch of old-school charm, the FiiO K11 R2R is a little slice of analog heaven in our digital world. And honestly, who couldn’t use a bit of that?

FIIO K11 R2R link : https://www.fiio.com/k11r2r

Disclaimer​

Ok, so todays reviewed FiiO K11 R2R was sent to me by FiiO for this review. This fact will not change my thoughts and opinions in this review, and every expression here is entirely my own! I've done my best to provide an honest review based on my experience with the product. My goal is to give you an accurate idea of what to expect if you decide to purchase the K11 R2R.
Furthermore, I really want to thank FiiO for providing me with this review unit and to thank you, the reader, for trusting in me and taking your time to read this review.

Introduction​

I recently got my hands on the FiiO K11 R2R, which is one of the most affordable integrated R2R DAC and headphone amplifiers you can find right now. At $159.99, it’s pretty exciting to see a device with this kind of technology. The K11 R2R stands out because it uses an R2R (Resistor Ladder) DAC (Its trickier to make correctly, but if done right, it should be something special...), unlike the more common Delta Sigma DACs in most modern gear. I've been curious to see how this would impact the sound and if it really brings that organic and natural sound signature that R2R DACs are known for...? Let's see what this little device has to offer...

Unboxing​

When I saw the FiiO K11 R2R package I immediately noticed that it was pretty basic and straightforward... The box had an image of the K11 R2R on the front with its name on it, and the box included exactly the accessories I had expected:

• the K11 R2R unit itself
• a USB data cable
• a power cable
• a power adapter
• a 6.35mm to 3.5mm headphone adapter
• and a quick start guide with a warranty card.

So the overall presentation was basic, but it included everything I need to get it going, which I think is great when considering the asking price!

Technical Specifications and Design​

Design:​

The design of the FiiO K11 R2R is really sleek and I like it a lot! It has a solid aluminum alloy body that makes it look and feel very durable and quality made. The unit I have is the black version and it gives me a clean vibe.
The front panel is simple but functional, with a large volume knob that doubles as a multifunction button. There’s also a 4.4mm balanced output and a 6.35mm single-ended output on the front, which is great for different types of headphones.
On the top of the unit is a big FiiO logo which lights up and you can even change the color, brightness and even the mode in which it lights up to whatever you want.
On the back panel you will find all the inputs and outputs, which includes; a USB Type-C, optical, coaxial, and RCA line-out, so it’s easy to connect to different devices. The whole thing is compact and fits perfectly on my desk without taking up too much space. Plus, it has a HUGE rubber pad on the bottom, so it stays in its place and wont move anywhere by itself!

About the R2R:​

The FiiO K11 R2R uses an R2R DAC, which is a different kind of digital to analog converter that relies on a resistor ladder to produce sound. What’s cool about R2R is that it can instantly hit the right voltage, unlike Sigma Delta DACs, which take small steps to get there whether it's higher or lower and even when staying at the same voltage. Those differences make it very audible! I really noticed that with this R2R DAC, I can hear that it is very quiet between notes.

Delta Sigma on the other side makes some audible hiss or buzz when music is playing, even if the DAC has no background noise and great specifications, but when something is playing, I can hear it; it is very noticeable when I am doing A-B tests. But it is important to remember that in general R2R DACs are not cheap... and that's because the tricky part with R2R is that if it’s not implemented well, it can introduce much more noise, especially with sensitive IEMs...

I actually did notice some of that noise when using the K11 R2R, but when I switched Tidal to exclusive mode, the noise was almost gone, making it much less of an issue. It’s really only noticeable when the sound is coming straight from the operating system. It's hard to exactly explain how the R2R sounds is, compared to the common Delta Sigma, But there are differences and you will have to try it to understand!

Gain Levels:​

The K11 R2R has three gain levels: low, medium, and high. This gives you the option for a more precise power control whenever you are using sensitive IEMs or more power hungry over ear headphones.

Low Gain: This one is good for IEMs or low impedance headphones, however the output impedance is pretty high... approximately 1.5 ohms for the balanced output and 1 ohm for the SE one. this makes low impedance IEM a bit challenging for this AMP to drive properly without distortion...

Medium Gain: A good middle ground, perfect for most headphones that don’t need extreme power but still benefit from a bit of extra push.

High Gain: This is where the K11 R2R shines for power hungry headphones. It delivers maximum output and is best suited for high impedance or less sensitive headphones. This one could drive my HE4XX and K712 Pro on 30%-40% volume, which is very good!

More settings:​

• SAM (Sampling): Over sampling (OS), Non over sampling (NOS)
• UAC: UAC 1.0, UAC 2.0
• LCD-B (Brightness): 1-3 brightness levels
• LCD-T (Screen timeout): 1/2/5/10/30 and 0 which means always on.
• RGB-M (Colors): 0/1/2/3/4/5/6/7/8 (Follow the audio/Red/Blue/Cyan/Purple/Yellow/White/Green/Or cycle all colors.
• RGB-P: Gives the option for the light to pulse or be constant.
• RGB-B (Brightness): 0(Off)/1/2/3/4/5
• IDLE (Smart Idle): On or Off
• UPDATE: Gives the option for a firmware update.
• RESET: Gives the option to factory reset all the settings.
• FW: Shows the firmware version.

Additionally, a very long press (I think about 5 seconds) turns the K11 R2R completely off, and to turn it back on, just press on the knob.

Specs:​

• Colors: Black, Silver, Red (planned for later production)
• Main control chip (single-chip microcomputer): GD32F303RET6
• DAC: Fully differential true 24bit R2R resistor arrays
• Volume control chip: NJW1195A
• USB input decoding: 384kHz/32bit, DSD256
• Coaxial input decoding: 192kHz/24bit
• Optical input decoding: 96kHz/24bit
• USB connector: Type-C
• Display: Custom LCD screen
• Dimensions: 147x133x32.3mm (including feet)
• Weight: About 420g
• Power supply: DC12V 2A external adapter
• SE power output 1: L+R≥460mW +460mW (32Ω, THD+N＜1%) (32Ω/single-ended/high gain)
• SE power output 2: L+R≥50mW+50mW (300Ω, THD+N＜1%) (300Ω/Single-ended/High gain)
• BAL power output 1: L+R≥1300mW+1300mW (32Ω, THD+N＜1%) (32Ω/Balanced/High gain)
• BAL power output 2: L+R≥220mW+220mW (300Ω, THD+N＜1%) (300Ω/Balanced/High gain)
• Frequency response: 20Hz~50kHz: attenuation＜1.3dB
• SNR: ≥115dB (A-weighted)
• Noise floor: PO＜7.2uV (A-weighted); BAL＜14.1uV (A-weighted)
• Output impedance: PO＜1Ω (32Ω load); BAL＜1.5Ω (32Ω load)
• THD+N: LO＜0.02% (1kHz/10kΩ)

Sound performance​

When it comes to sound, the FiiO K11 R2R has a really unique character that stands out from other DACs I've used. The first thing I noticed was its warm and natural tone. The bass has a nice punch to it, yet without overpowering the rest of the sound. And I will add more... Despite the warmer tone the sound is very detailed! It’s not as detailed as some other DACs, but its details make through in another way, which is different from a regular Delta Sigma DAC...

As I said, the sound of this r2r, at least the way it goes through the amplifier there... sounds warmer yet still "analytical" (not in the term of high frequencies, but rather the way each note is delivered...), as if there is less smoothing. Things sound sharper, and not necessarily in terms of high frequencies...

I can describe it as having the feeling that between notes there is silence compared to other Delta sigma DACs I have.

You can imagine this in way that the R2R can reach each frequency almost instantly compared to the steps of voltage in Delta Sigma.

Now the mid range of the K11 R2R, which adds a bit of warmth, especially to vocals and instruments like guitars and pianos. Vocals come through with a smooth quality, which is nice for genres like jazz or acoustic music. Yet even in more complex tracks, the mids are never muffled and stuffed together because of this R2R characteristic! like the different elements have their own moments in the track and each sounds very detailed without any smoothening and noise between notes.

The treble is where the K11 R2R shows its softer side. It doesn’t have that sharp, sometimes harsh edge that can make listening fatiguing. Instead, the high notes are smooth and easy on the ears which makes it great for long listening sessions. The best part is, that it doesn't lose too much detail, even though its sound signature is warmer.

NOS and OS modes:​

One of the interesting features is the ability to switch between No Over Sampling (NOS) and Over Sampling (OS) modes. In NOS mode, the sound is even warmer and more relaxed, almost like listening to vinyl. It’s great if you want a really smooth and organic sound, almost (but definitely not) tube like. On the other hand, the OS mode tightens things up a bit, adding more detail and clarity, especially in the mids and highs. I found myself using the OS mode more often because it strikes a good balance between warmth and detail.

Overall, the K11 R2R offers a sound that’s more about enjoying the music! It’s a bit like sitting back and letting the music wash over you. And even if you want to hear details, you don't need to struggle with analyzing the sound, you can still lay down and enjoy the details.

Conclusion​

So after spending some time with the FiiO K11 R2R, I can easily say that it’s a solid choice for anyone looking to step into the world of R2R DACs without breaking the bank!

The warm and natural sound, yet still detailed (in its own way...) sound is its standout feature which makes it a pleasure to listen to, especially if you are into a more laid back and organic sound. And the ability to switch between NOS and OS modes adds some versatility, which is great for when I'm having a different listening vibe.

However, it's not without its quirks. The K11 R2R isn’t as powerful (although I had enough power for any of my harder to drive headphones... but some people may find it lacking...) or as technical as some of its competitors. There's also a noticeable background noise issue with sensitive IEMs, but it’s mostly manageable if you’re using exclusive mode.

In the end, the K11 R2R offers a unique and enjoyable sound that stands out from the common Delta Sigma DACs. So If you value a natural and analog like sound over absolute technicalities, the K11 R2R is definitely worth considering, especially when taking into a count its price point! And I really think that it is a great entry into the world of R2R which offers a sound that’s both engaging and easy to live with for long listening sessions.

General/Packaging/Build
Fiio is a brand that needs no introduction to fellow audiophiles, they are well established and they have positioned themselves among the top few famous chi-fi brands. I reviewed the K11 early this year and they proved to be highly competitive in terms of price performance ratio. Fast forward today, I have the Fiio K11 R2R with me which Fiio swapped out the CS43198 with R2R DAC resistor array, of course it is not as simple as just swapping out the dac without some redesign on the circuit. I will not go into detail into this as I'm not an electrical engineer myself. The packaging is quite good for the asking price, it contains a power supply unit, USB cable and the K11 R2R itself, well protected from any mishandling during transportation/logistics. The build quality and the overall dimension is similar to the K11, even the inputs and output, the only nitpick that i have is the lack of balanced output

Specifications

• You may refer to this link from Fiio’s official website for the detailed specifications

Gears used for this review

• Macbook Air M2 -> Foobar/Tidal
• Fiio K11 R2R -> Aune S9c Pro
• Fiio FT3 32Ohm
• NF Audio NE4
• Spirit Torino Twin Pulse IEM

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

Driving Power

• While the power output has been reduced from 1.4w to 1.3w for the K11 R2R, i personally don’t have any issues driving the gears that i have, low gain is sufficient for most IEMs, high gains on the FT3 has got very good dynamics, mid gains on the Twin Pulse IEM also exhibits very good dynamics and overall presentation, using it with high seems to leave the Twin Pulse IEM with not much headroom

Features

• 3 Gain levels, low, mid and high
• RGB logo with adjustable lighting effect on the device itself
• Upgradeable firmware

Sound Impression (NOS and OS)
The tuning of the K11 R2R is warmish sounding and analog-ish with the dac/amp running on NOS sampling mode based on my listening experience. The mids are quite intimate sounding but at the same time, they are not overly forward. The note weight is quite good and it is certainly not thin sounding. Soundstage is not that big or grand in NOS mode, imaging is acceptable and good enough for the asking price, but of course, do not expect it to have pinpoint accuracy compared to higher priced dac/amp.

OS on the other hand boast a slightly better resolution and technicalities compared to NOS mode, everything sounded a little bit more crisp compared to NOS mode, and it isn’t as laid back.



Listening Impression with the following gears
Fiio FT3 32Ohm

• FT3 is very efficient and easy to drive, Low gain on K11 R2R is sufficient to power the FT3 to its best performance,on mid gain the dynamics are slightly better and also the bass control is slightly tighter, high gain is not needed here
• Bass is punchy and tight, mid bass especially
• Sub bass has slightly better extension, mids are slightly a bit more forward and exhibit slightly thicker note weight which benefited from the NOS mode
• Male vocal has slightly thicker texture and sounds fuller
• Female vocal is slightly fuller sounding, which is also a benefit from the NOS mode
• Not so much changes in terms of detail retrieval
• Overall, a very good synergy

NF Audio NE4 (Reference Faceplate)

• NE4 with the reference faceplate
• The mids are slightly recessed, but when paired with K11 R2r, the mids doesn’t sound that recessed anymore and it sounded a little bit more forward, both male and female vocal have a little bit more “body”
• Bass on the other hand sounds a little bit more impactful when paired with K11 R2R, the sub bass rumble is still quite strong but somehow i feel like it has a slightly faster decay, but mid bass is still punchy, a very refreshing experience if you ask me, still very fun sounding,
• Not much changes on the detail retrieval as well
• Soundstage is more or less similar
• NE4 is not hard to drive, and K11 R2R definitely have more than enough power to push it to its maximum potential

Spirit Torino Twin Pulse IEM

• Twin Pulse IEM is a dual DD in isobaric config from the italian brand Spirit Torino
• The sound signature is leaning towards neutral with a slight hint of warmth on the default nozzle, pairing it with the K11 R2R, it does made the overall experience more musical and emotional but at the expense of sacrificing a bit of resolution as well as imaging on NOS mode
• The OS mode on the other hand does have slightly better resolution as well as imaging, setting the gain to mid does exhibit quite good dynamics and slightly cleaner sounding experience, i personally prefer the OS mode for the Twin Pulse as the NOS is a bit too laid back

Line Out Sound Impression ( RCA Out to Earmen ST-AMP )

• The R2R DAC on K11 R2R has good potential in my opinion, i’m not saying the the amping section of the K11 R2R is bad, i think that we can squeeze out a little bit more from the DAC by pairing it with a better amp
• The ST-AMP is not a pure amp, but the amping section is quite good and it is able to squeeze out a bit more details from the R2R dac, and to my ears, slightly better resolution while retaining the warmth and analog factor from the NOS mode
• Dynamics does improve a little bit as well, quite a good pairing i would say
• On the lineout mode, i do noticed a very minor pop sound as reported by several other reviewers which one of them is also my friend

Comparison (Fiio’s K11)

• In terms of sound, The K11’s sound signature is leaning towards the clean sounding kind of tonality, less warmth and slightly thinner note weight compared to K11 R2R
• Power output figure is slightly higher compared to K11 R2R, but i would say the difference is minimal unless you have a lot of hard to drive gears, else there isn’t much difference in your listening experience as well as day to day usage
• Depending on your preference in terms of sound signature, the K11 a more clean/technical sounding overall, whereas K11 R2R has warm and analog sound signature from the NOS mode, i wouldn't say the K11 R2R is a replacement or upgrade over the K11, but rather, a different device targeted at different group of users

Final Thoughts
Having tested the K11 R2R for several weeks now, it’s safe to say K11 has a very high price performance ratio, i believe i have not seen any R2R Desktop DAC/Amp at such pricing, and despite being the first R2R dac/amp from Fiio, they actually nailed it, and i personally think that this model is paving way for their mid or higher end models, which if it does happen, i am definitely anticipating it. In terms of sound, It sounds musical and analog-ish as I have mentioned, and I personally like how it sounds whereby you’re able to connect with the song emotionally. K11 R2R ticks many of the boxes in terms of features as well as sonic performance. K11 R2R is definitely one of the good products that is easily recommendable and won’t break the bank. Definitely a 4.5/5 product! Not to mention this is R2R DAC rather than the usual Delta Sigma DAC



*A big thanks to Fiio for sending this over for the purpose of this review. I thank them for their support and opportunity

Head over to their official store if you are interested in getting one:

Fiio K11 R2R Official Store Link - Non affiliated
Fiio K11 R2R Product Page

DISCLAIMER

This unit was purchased at a discounted price from Aliexpress.

The Fiio K11 R2R can be gotten here: https://www.aliexpress.com/item/1005007369579700.html (no affiliate links).





INTRODUCTION

This model is the sequel to the original Fiio K11 destop DAC/AMP, which was a Delta Sigma set, utilizing a Cirrus Logic CS43198 chip. The K11 R2R we are talking about today - as per its namesake - packs an R2R chip, and is as of the time of writing, one of the cheapest R2R desktop devices.


SPECIFICATIONS

Tested at: $169.99 USD

For the measurement-inclined, do check out this page for further specs: https://www.fiio.com/k11r2r_parameters.

I'm not an Apple ecosystem user, but the K11 R2R paired easily with various Windows laptops/PCs, Android smartphones and DAPs. For Windows 10 and above users, this device is plug-and-play without the need to install additional drivers.


ACCESSORIES

Other than the K11 R2R, these are included:
- 6.35 mm to 3.5 mm adapter
- 1 x USB-A to USB-C cable
- Power plug (DC 12V 2A) with adapter



The inclusions are more than decent for a $100ish desktop amp, with the only exception being the lack of Apple adapters for this subset of users.


DESIGN/FUNCTION



This amp is square shaped, with rounded edges that won't poke users. It is solidly fashioned from matte aluminum alloy. During ordering, one can opt for a silver or black K11 R2R. There is apparently a Ferrari red chassis variant that will be soon released in the near future, so keep your eyes out for that!



Weighing 420 g - and measuring 147 x 133 x 32.3 mm - this DAC/AMP is very unobtrusive and compact for a desktop solution. It can be laid down flat as part of a stack, or stood up vertically to save space. There are anti-slip rubberized feet at the bottom for grip.



The front of the device sports a 6.35 mm (single-ended) and 4.4 mm (balanced) port. One can plug in the provided 3.5 mm to 6.35 mm jack if you need to pair a 3.5 mm terminated transducer with this device The front panel also has a gorgeous LCD screen and a volume knob.

On the LCD screen, one can glean information such as sampling rate, volume, gain and output/input mode.

Other than controlling volume as per its namesake, this all-important knob also performs the following functions:

• A power off button - hold it for 5 seconds.
• Short pressing toggles between USB in, optical in and COAX in.
• Double pressing brings us to the PO, PRE (LO single-ended) and LO mode - the K11 R2R even remembers the last volume level in each mode independently!
• Pressing the knob for 2 seconds triggers the settings menu.

From the settings menu, we can access gain modes, output modes, OS/NOS modes, USB UAC modes (for our gaming brethren), and adjust screen brightness, lighting settings/colours, and time-out adjustments.

I'm quite happy that the volume steps are finely divided into 100 divisions, allowing close control of the volume levels. There is a haptic click felt with each turn of the knob, unlike some other amps that are a bit loose on turning the dial.

This sole volume knob controls all the functions; while it seems quite solid, I'm not sure that with prolonged usage, if this button gets worn out, we might be left with a white elephant.




On the back of the DAC/Amp, we have the power supply, USB-C, optical, co-axial and RCA ports.

The top of the device has a fetching RGB lighting, with 7 gradations of colour.

The K11 R2R is powered via 17 low-noise LDO precision regulators with a 12V power supply with inherent DC protection. It has a nifty power saving feature to enter low power mode when no audio input is detected after 30 min, to conserve energy.





While there is an intelligent anti-pop array installed on the front panel on the 3.5 mm and 4.4 mm inputs - so that there is no nasty pop heard on disconnecting or inserting transducers - unfortunately there is some mild pop heard on line-out mode when switching modes.

Hiss is present in minute quantities with very high sensitivity IEMs, but is by-and-large not too noticeable.


INTERNALS

As previously mentioned, this DAC/AMP is one of the more unique ones at its price point, utilizing a fully discrete 24-bit R2R DAC resistor array, instead of the more common Delta Sigma DACs.



We have 2 x 48 precision thin resistor arrays on each channel, with 0.1% tolerance and a 30 ppm low temperature difference. Beryl solid capacitors coupled with NJW1195A volume controllers are installed within.



The K11 R2R allows playback of up to DSD 256 and PCM 384 kHz/32-bit on USB-input, and 192 kHz/24 -bit on coaxial, with 96 kHz/24-bit on optical input.

This device has no DAC filters, but we have 2 modes - the NOS and OS mode - which we will discuss in detail below. The K11 R2R has no inbuilt PEQ too.

I like that this amp runs cool to the touch, with a well designed cooling system.




SOUND

Sound-wise, the K11 R2R has an oversampling (OS) and non-oversampling (NOS) mode.

The NOS mode reprises the classic R2R signature, where this amp sounds analoguish, with a thick note weight, weighty bass, and a tamed upper mids/treble. It is quite tube-like and is an excellent pairing for edgier transducers, or for folks who wanna sit back and relax to the music. Edge definition to notes are rounded off to remove fatigue, though micro-detailing takes a backstage. The sound is rather "euphonic".

The OS mode is neutralish, thinner and more resolving, something more analytical than what the NOS brings to the table. This is more akin to the usual Fiio house sound that we are familiar with, and is an option for the analytical heads. Soundstage and resolution improves on this setup.

Thus, we do have 2 quite distinct tunings on the K11 R2R, depending on what you desire. It is kind of getting 2 amps in one! Timbre is really organic and natural on the NOS mode, whereas we get a bit of a more sterile soundscape on the OS mode.



Power-wise, the K11 R2R has 3 gain settings, and outputs 460 mW (32Ω) and 1300 mW (32Ω) for the single-ended and balanced ports respectively, which is more than enough for most gear out there, other than outlier behemoths.

Output impedance is ＜1 Ω on single-ended and < 1.5 Ω on balanced ports, so the single-ended one is quite useful for low impedance fussy IEMs (based on the rules of eights), so as not to skew the frequency response. The OI on the balanced port is a bit higher, so it may make low impedance IEMs sound bassier, and is probably best reserved for harder to drive stuff.


COMPARISONS

I'm sure some readers will ask how does this R2R DAC/AMP compete with one of the other gatekeeper R2R devices in the Cayin RU6 - which admittedly is a bit unfair as that is a dongle - but to get this out of the way, the K11 R2R kills the RU6 in technicalities and power output, and is a more refined source overall.

So let's move on to comparing it against similarly priced desktop setups, which is a more fair battle.


Topping L30

The L30 is a sterile and analytical kit; it eschews musicality for the critical scalpel of dissecting music. The L30 has a much thinner note weight and is sharper and more fatiguing in the upper mids/treble, even when compared to the K11 R2R on the more resolving OS mode. The L30 uses some overly boosted upper frequencies to generate "fake details", whereas the K11 R2R is more natural on OS mode, while still capturing clarity and micro-details. For timbral accuracy, the L30 is more metallic-sounding.

The L30 is only single-ended but also has 3 gain settings. However, juice-wise, it beats the K11 R2R even on balanced, with 2300 mW into 32 Ω. Thus, the L30 can pump harder to drive transducer outliers.

The L30 gets way warmer during usage, and earlier batches were actually recalled due to electrostatic discharge and grounding issues that destroyed a few headphones (https://imgur.com/v5Ja7f3)!


Fiio K11

The original K11 houses a Delta Sigma DAC in a Cirrus Logic CS43198 chip. The original K11 is marginally more powerful, outputting 520 mW @ 32 Ω and 1400 mW @ 32 Ω on the single-ended and balanced ports respectively.

However, the predecessor K11 has a higher output impedance of 2.4 Ω and 1.2 Ω on the balanced and single-ended ports, which is worse than that of the K11 R2R, so the younger sibling boasts of an improvement in OI.

The original K11 has the typical neutral bright and analytical Fiio house sound, but it has some DAC filters to play around with. On OS mode for the K11 R2R, it is an upgrade over the older sibling K11, as the former furnishes better soundstaging, micro-detailing and imaging.

Truly, with the advent of the K11 R2R, it has made the original K11 obsolete, other than a slight power reduction.


The OG K11 (in silver below) is literally trumped by the new K11 R2R (in black above).


CONCLUSIONS



The K11 R2R is an affordable desktop kit, and arguably one of the cheapest R2R containing desktop devices presently. While there are no DAC filters, there is a more resolving OS mode and an analoguish laid-back NOS profile, so one is getting 2 tunings with a single purchase.

Other than the solid price-to-performance at its $100ish pricing, there is good power available with 3 gain settings, all housed within an attractive and compact profile, coupled with robust build. The volume steps are implemented well in terms of levels, and the K11 R2R runs cool during usage. It also has multiple inputs and outputs, and even a USB gaming mode for our gaming enthusiasts. I would have preferred additional buttons other than the sole volume knob that handles everything, but that is a nitpick.

The K11 R2R is not the most powerful desktop amp at its price point, but can definitely drive most stuff sufficiently - especially on balanced mode - other than rare outliers. While there is no pop noted on inserting or removing transducers from the 6.35 mm and 4.4 mm ports, the LO mode does have some popping on switching modes.

There is also very minute hiss noted on sensitive gear, but overall, this DAC/AMP is an all-rounder device with great value proposition. It has even made the predecessor original K11 antiquated, so for folks who want to sample an R2R desktop machine for a non-kidney donating price, this is a recommended purchase.

FiiO K11 R2R

FiiO K11 R2R
INSTAGRAM: LINK

Prelude:
FiiO is one of the fastest growing audio brands in the world. Its origins date back to the times when technology mattered in audio, not cost cutting. At the same time, the basic principle and basis of the philosophy represented by FiiO is an excellent, sometimes even astonishingly good value for money. The K11 model, reviewed by me some time ago, turned out to be a great and very versatile device with a very solid musical attitude and wide functionality. You are probably wondering what changes the K11R2R can bring compared to the original K11 model. Well, let me start with the most obvious change, which is a small increase in price, because the original K11 costs 129 USD, while for the R2R variant we will have to pay 169 USD, which is 40 USD more. Is such a price change justified? Well, in my opinion, it is an indecently low increase in price considering the cost and time of work that FiiO put into the development of a completely new technology for FiiO. FiiO K11 R2R has a redesigned power supply, an FPGA system has been added, and a completely new DAC, which is an analog R2R system developed entirely by FiiO. Apart from these changes, everything else has remained unchanged. Well, almost, because to my great joy, FiiO has expanded the linear output in the K11R2R model and now we have a choice between a regulated pre output and a fully linear output with a fixed signal level. For those who complain that there is no balanced output, I will immediately point out that most likely there was simply no space on the housing. I do not consider this to be a disadvantage in the slightest, because the price at which the FiiO K11R2R is offered is a robbery in terms of value for money anyway. To tell you the truth, I will use a small spoiler and tell you right now that in my opinion, the FiiO K11 R2R has huge potential to become the king of profitability up to 200 USD.
Unboxing and Ergonomics:
As is already the case with my reviews, the next point I would like to address is how we receive the equipment. As I have already mentioned, the FiiO K11 R2R model is a variation of the K11 model, so it will not be a surprise that we receive the same well-known set packed in a nice cardboard box. Inside, we will find a switching power supply with a plug compatible for our geographical region, as well as a USB C cable and an adapter from a large jack to a small 3.5 mm jack. That’s all for the equipment. The device itself is identical to the K11 model, and for those who have not read my K11 review, I will remind you of a few facts. First of all, we have a completely metal housing with very compact dimensions. There is also a 4.4 mm balanced output and a classic 6.5 mm large SE jack. On the input side, we have an optical, coaxial and USB C input. On the output side, an interesting feature is the presence of a coaxial output and a fully functional RCA output. It can function as both a preamplifier and a fixed power amplifier. The body and dimensions of the FiiO K11 R2R are completely identical to those of the K11.

Sound:
Bass: Low tones go low, are very plastic and have a classic analog soft character. Importantly, a lot depends on whether we choose NOS or OS mode. In the case of NOS mode, we have more warmth and an analog sound structure closer to the original. If we decide on OS, i.e. additional oversampling, our sound will become even clearer and a bit more technical. In general, the low tones in the FiiO K11 R2R have a very clean and natural character. They bring a lot of pleasure to listening and delight with their smooth and expanded character. Regardless of what music genre is currently our first choice. Low tones are also not overwhelming or overly exposed over the rest of the band. The built-in amplifier in the K11 is quite neutral, which balances well with the warm and analog character of DACs based on the R2R architecture.

Mid-tones: Actually, since the main difference between the K11 and the FiiO K11 R2R lies in the DAC system, and the R2R systems are associated with the extremely emotional side of the mid-range of music, it probably won’t surprise anyone that FiiO has focused on analog and warmth here. We have a lot of emotions and engaging and engaging vocals here. They lack neither saturation nor mass. The tone is warmer, but we don’t have too much sweetness here. If any of you were wondering which way FiiO will go with the first R2R product, in my opinion it is a healthy balance that maintains the technical layer and a pleasantly warm and, most importantly, natural sound. The sound stage is large, we have a very good arrangement of instruments and a wide and deep presentation. I perceived the vocals as closer and more direct, slightly exposed to the front. However, this perfectly matches the empirical and direct message that the FiiO K11 R2R builds in its presentation.
Highs: This area has been warmed up, the excessive exposition of details has been abandoned, instead the charm and magic of R2R has been focused on. We have here a great smoothness and coherence with the rest of the presentation. I liked how much emotion and natural character the tracks served by FiiO K11 R2R contained. The highs perfectly complemented the vocals and the low ranges. I did not feel that I was missing anything.
Headphones and equipment used during the review:
Headphones I used: SoftEars Volume, OllOaudio s5x, HifiMan HE1000SE, Hifiman Svanar and ThinkSound OV21. Equipment I used for reference: HifiMan EF600 R2R DAC, FiiO K11, EarMen ST-AMP. Music is classic Tidal and my own files.

Comparisons:

FiiO K11 R2R (169USD) VS FiiO K11(129USD)
FiiO K11 R2R is a more analog, exciting sound with a warm and engaging sound. It impresses with the quality of sound and build quality. The classic K11 model is more clinical, a bit more technical with more technical details and a more digital presentation. The classic K11 model offers less warmth and naturalness, but rewards with a more digital and colder sound, which may work for other preferences, which is why I rate both devices very well, they are similar, but they differ in sound to such an extent that they complement each other perfectly.
FiiO K11 R2R (169USD) VS EarMen ST-AMP (199USD)
ST-AMP is a less even sound, more focused on musicality and entertainment, offers a larger soundstage, while FiiO K11 R2R focuses on the intimate and emotional side. Importantly, FiiO K11 R2R can be used only as a DAC/AMP or DAC, while ST-AMP is also a standalone amplifier, which perfectly paired with FiiO K11 R2R as a DAC.

Fiio K11 R2R (169USD) VS HifiMan EF600 (700USD)
It is obvious that in many categories EF600 simply wins, but here I would like to focus only on the comparison DAC R2R VS DAC R2R. FiiO is a more analog and warmer sound, much more direct. While EF600 is a more technical approach to R2R circuits and a much brighter more resolved sound. Both systems are emotional and natural, but FiiO is more warm and analog, and EF600 is faster pace and more technical layer.

Linear and pre mode:
In the linear output mode with constant power FiiO K11 R2R is extremely warm, analog and plastic, which can be easily changed by changing the mode to OS. This will make it more technical, but will not kill the sweetness and smoothness of the R2R system. When it comes to using it as a pre-amplifier, FiiO provides a clean signal and very smooth volume control via a digital potentiometer.

Power:
Although k11 R2R has a bit less power than the basic K11, it is still enough for most basic and even better, more demanding headphones.

Summary:
FiiO K11 R2R is an amazing device that made a huge impression on me. Maybe it is because of my personal love for R2R sound. Although the classic K11 is an equally great device with a very good technical presentation, the R2R variant provides an even more refined sound. In addition, the R2R model has a fully functional line output, not just a volume control. In terms of sound, the FiiO K11 R2R can successfully compete with much more expensive systems. In my opinion, if someone is looking for a natural and emotional sound, the FiiO K11 R2R is just like that. It is a modern version of a classic that makes music even more tangible and engaging. The only thing I personally recommend is changing the power supply from switching to linear, which will improve the sound even more. That is why I highly recommend checking out this amazingly good DAC/AMP for yourself at a budget price, with sound quality well above the quality suggested by the price. It is worth mentioning that although the FiiO K11 R2R will not play as a stand-alone amplifier, thanks to the way FiiO has tuned this equipment, we have a fully autonomous and completely self-sufficient unit. What is equally impressive is the quality offered by the line output in the FiiO K11 R2R. I connected the K11 R2R using 1.5m FiiO LR-RCA4 RCA cables to my favorite CH-AMP and what I heard was pure magic. The sound became elastic and soft, it gained even more details and details. In a word, it became even fuller and even more delightful. Let’s stop for a moment at the FiiO LR-RCA4 RCA cables, these are relatively inexpensive and beautiful-looking braided cables. They were made of high-quality materials and in my audio system, their use resulted in a cleaner and more engaging sound. It is important that the entire path in our system is consistent and properly selected. I am all the more glad that FiiO is a manufacturer who took care to provide us with not only great equipment, but also excellent accessories that match them.

​

R2R goodness comes to the K11​

FiiO had built an incredible good headphone amplifier with the original K11, it had in my opinion, the right balance of power, features, good looks and price that made it a fantastic pragmatic device.

And it is one that I still use in my living room setup, but that might now change.



Given how similar the K11 R2R is to the original K11, please refer to my previous review of the K11 here for more details on the original. I will concentrate on the aspects of the K11 R2R that are unique.

I find it fascinating that FiiO have adapted the same design but replaced the internal DAC architecture with an R2R ladder DAC (which they have built themselves) in the new K11 R2R, so I thought it might be useful to include some technical details on R2R DACs also within this review.

Note: I would like to thank FiiO for providing the K11 R2R for the purposes of this short review.
To find out more details you should head over to the FiiO product page
So the new K11-R2R any better than the K11, read on to find out but first some ‘background homework’ on R2R DACs:

What is a R2R Ladder DAC and how do they sound?​

A Resistor-to-Resistor (R2R) Digital-to-Analog Converter (DAC) is a type of DAC that uses a network of precision resistors to convert digital signals into analog output. This architecture contrasts with delta-sigma DACs, which use oversampling and noise shaping techniques. The R2R ladder DAC employs a series of resistors with precise values arranged in a ladder configuration. Each step of the ladder corresponds to a bit in the digital signal, and the combination of these resistors translates the digital input into a corresponding analog voltage.

Due to the precision required in the resistor values, high-quality R2R DACs can be expensive and complex to manufacture, which is why it is amazing that FiiO have managed to upgrade their K11 design with a R2R DAC yet keep the price very reasonable. R2R DAC’s are valued for their direct and straightforward approach to digital-to-analog conversion, there people will talk about a less ‘digital’ sound to R2R DACs. In my listening experience in the past I found they sound more ‘organic’, maybe landing between the more clinical sound of Delta Sigma DACs and the something crazy harmonics of DAC with a Tube Amplifier stage.

In terms of sound quality, R2R DACs are often praised for their natural and engaging sound signature. They tend to produce a smooth and coherent musical presentation with excellent tonal balance and a rich, analog-like warmth. Listeners often describe the sound as having a more organic and lifelike quality, with a natural decay of instruments and voices. The R2R design is known for its excellent transient response and detailed micro-dynamics, providing a sense of realism and presence in the music.

However, it is important to note that the sound quality can be influenced by various factors, including the quality of the resistors used, the overall design of the DAC, and the implementation of the surrounding circuitry.

I was lucking enough earlier this year to do some A/B testing between 2 similar devices on with an R2R DAC was with the Hifiman Svanar Wireless Jr and LE. In that comparison it was really no competition between the ’normal’ DAC and the Himalaya R2R DAC, there was an expansive sound stage and excellent dynamics coming from the R2R DAC. So, I have high exceptions for the K11 R2R.

FiiO Provided this architecture diagram on their website about how they fitted their custom-built R2R DAC within the overall K11 architecture:

What’s in the box​

As you would expect from FiiO the packaging is excellent and obviously the K11-R2R is very similar to the K11 packaging:




Opening the box and again similar to the K11, you get 2 separate boxes one with the power supply and some accessories and the other with K11 R2R itself:


Here are the complete contents laid out:


Looking at the K11 R2R itself in detail:

The new K11-R2R and the original are effectively identical:

Basically the R2R branding is the only difference you will notice:

From the front they are identical:

and also from the back:

So, the real differences are internal but there are some changes to the features, lets have a quick look at the different features of the K11 R2R compared to the original.

Features Changes​

So the K11-R2R keeps all the excellent features of the original like the 3-gain levels each with an independent volume curve the powerful headphone output, but you can read about those capabilities in the original K11.

So the main difference in the configuration of the K11-R2R is removal of the typical delta sigma filters that was available on the original K11 and the 2 ‘sampling’ options you get on the K11-R2R, specifically no over sampling (i.e. pure R2R) or Over Sampling:


So I thought it might be useful to have a brief capture of the menus on the K11-R2R - which are still controlled the same way using the ‘volume’ pressing and holding to activate the menu, rotating to move between menu options and a single press to switch specific settings:

Sound Impressions​

So the most important change is how does it sound?

I think the best word to describe the sound is organic. Where the original K11 and other FiiO DACs in the past have been very analytical trying to deliver the most accurate representation of the original audio, the K11-R2R while tonally it is accurate, it adds a little ‘harmonic’ nature to the sound. R2R DACs were extremely popular back in the early 2000’s and were very expensive and the K11-R2R sounds like an expensive DAC from that period.

So, this sound won’t be for everyone, but I think for those who crave a less ‘digital’ sound from their headphone amplifiers will love it. It not quiet tube amplifier level but for a fraction of the price you are getting a beautiful R2R DAC reconstruction of the music. I was also mainly listening with the NOS configured via the menus as show above.

I was mainly listening to this with some planars, FiiO FT5 and my Hifiman Edition XS and in both cases I thought it bought out a depth to the music that I didn’t get with the original K11. . So for example, with Massive Attacks Angel the ‘stage’ was much more layered than you would expect at this price point. The bass was punchy but never overpowered the midrange and there was lots of both width and depth to the sound.

For more ’three-dimensional’ music, I then switched to Tool’s Chocolate Chip Trip the swirling sound was immense and the percussive dynamics elements of the various drums in the song where extremely well presented.

For a bit of retro music, as I do feel R2R DACs (like Tube Amps) work best with music recorded in analog, restoring that analog sound, I switch to Bowie’s classic Ziggy Stardust album and tracks like Soul love sounded fantastic, really bringing back that analog sound. I then spend the next few days revisiting so many fantastic 1970’s albums, from Roxy Music, Elton John, Pink Floyd (of course). It was like listening to these classics with fresh ears.

So this was fantastic but one or 2 little caveats, I was switching different sources and I believe unless you have a perfect source you will occasionally either hear a noise floor or will lose enough dynamic range to be significant and your music will not be quiet as precise as you would like. So I would careful match the K11-R2R this with a good quality streamer for the best performance.

Measurements & Specifications and technical comparisons​

First lets look at the specifications:

Specifications​

Overall:

Line out:

SE output:

Balanced Output:

For me the key specification to look at are the output power, and thankfully you will see that the K11 R2R has similar power to the original K11 especially over the balanced output.


So roughly about 90% of the same power as the original which is great.

Measurements​

So if you are into measurements or more specifically into AudioScienceReview SINAD scores I would look away now.

R2R DAC’s (like Tube Amps) will always measure badly as they typically reconstruct the sound with some harmonics. The trick is normally to use ‘good’ harmonics which sound pleasant and enhance the qualities of the sound.

So FiiO provides an insightful graph on the product page:


So the trick is usually to have the right harmonic ‘spikes’ an analytical amplifier will minimize all of these spikes, while an R2R DAC will have the good harmonic ‘spikes’ while minimizing the other ‘spikes’.

So if you were scanning the specifications above you will notice the THD+N from all outputs are roughly the same 0.025% this is actually good for a R2R DAC but if you follows ’numbers’ this is poor compared to what you can get with a Delta Sigma DAC (like the K11) which has a THD+N score of 0.00059%.

FiiO to their credit are not hiding the measurements but in the interests of completely in this review, I thought it might worth comparing FiiO own measurements from both the original K11 and the K11R2R.

Original K11 THD+N graph:


and the now the THD+N level for the K11-R2R:


But beyond the THD+N level which is really the harmonics generated by the R2R process, other measurements of the K11-R2R were pretty good, there is no weird tonality ‘colouring’ as the Frequency response is ‘flat’:

If you are interested in more details, I would check out FiiO specification page for more details.

Rating:​

I gave the K11-R2R a pragmatic rating of 4, it offers amazing value for money for a R2R DAC and has similar features and build quality to the original K11. The R2R DAC while it does make a sonic difference giving you a more organic sound rather than the analytical sound of the original K11. I do feel this won’t be for everyone but for the price it means having an excellent R2R headphone DAC is now something everyone can now afford.

I have really enjoyed my few weeks listening to the K11-R2R, and it has especially given me new appreciation for older music in my older collection, but I personally will switch back to the original K11 though this is more about wanting and needing to listen something that is analytically neutral, when evaluating other audio equipment.

Summary:​

The K11-R2R is an amazing bargain and for those looking to try something which is normally only available at significant more expensive price range. While it has been fun, like catching up with old friends, ultimately it probably isn’t for me, but I hope in this review I have given you enough impressions that it may well be the perfect headphone amplifier for you.

Disclaimer: FiiO has provided me with a review unit ahead of the launch. All thought and opinions are my own.

Introduction​

Many people would recognize FiiO from their excellent line of DAPs and DAC/amp combo in the past. For the longest time, their house sound is often being categorized as being too clinical, especially with the recent push of THX amp modules in their recent products further adding into that stereotype. I personally found that it is true to a certain extent, but once in a while, FiiO did come up with some products that avoided that “house sound” trend, such as the Q7, Q15, M17, and more, which are more tastefully “coloured” compared to their compatriots.

The entry level K11 ($129) was released sometime last year to somewhat of a warm reception. It was a very value-oriented product, a very clean DAC/amp combo with a pretty powerful headphone amp (matching its discontinued older brother the K5 Pro) at a much smaller physical size. What I didn’t expect was that FiiO was planning a plot twist: K11 R2R ($169).

R2R is often associated with having a more analogue sound signature, with organic tone and less aggressive technicalities. Also, R2R is also often quite expensive, making the K11 R2R one of the cheapest R2R devices on the market, even cheaper than the Cayin RU6 R2R dongle DAC/amp at launch. Now, will the K11 hit the mark again with its R2R cousin? Let’s find out!

Packaging & Build​

For an entry-level product, the packaging is pretty spartan. Inside the pretty thin box, there are the unit itself, USB C-to-C cable with USB A adapter, power supply (3-pin grounded, my preferred kind), and 6.35mm to 3.5mm adapter. As I am residing in the country with UK power socket, FiiO has kindly included a UK power cable outside of the box.



I have no complaints about the packaging, especially given the price point. The build quality, however, is very solid, almost like a Mac Mini (especially the silver option). There is an LED light on top of the unit in the shape of the Fiio logo that’s pretty bright. Fortunately you can indeed dim it or turn it off from the settings should you want it. In front, there is a monochrome OLED screen showing basic information regarding the device status. A digital encoder acts as a volume control as well as power button and menu navigation. There is no Bluetooth capability.

At the back, you can see the 3 different digital inputs: USB, optical, and coaxial, along with single-ended RCA lineout and power input. While I do wish for a balanced lineout (maybe 3.5mm for single-ended and 4.4mm for balanced lineouts), I think that’s just a nitpicky wishlist.

Specifications and I/O​

DAC: Fully-differential true 24bit R2R resistor array
Amp: Dual SGM8262-2
Ports: USB, SPDIF optical (input and output) and coaxial

Single-ended headphone output (6.35mm, OS mode):

Output power:
L+R≥660mW +660mW(16Ω，THD+N＜1%)
L+R≥460mW +460mW(32Ω，THD+N＜1%)
L+R≥50mW+50mW (300Ω，THD+N＜1%）
Channel crosstalk: ≥72dB
Frequency response
20Hz~50kHz: damping＜1.3dB
20Hz~20KHz: damping＜0.2dB
THD+N: About 0.025% (1kHz/0dB@32Ω)
SNR: ≥115dB (A-weighted)
Noise floor: ＜7.2uV (A-weighted)
Dynamic range: ≥107dB
Output impedance: ＜1Ω
Peak output voltage: 11Vp-p

Click to expand...

Balanced headphone output (4.4mm, OS mode):

Output power:
L+R≥520mW+520mW (16Ω, THD+N＜1%)
L+R≥1300mW+1300mW (32Ω, THD+N＜1%)
L+R≥220mW+220mW (300Ω, THD+N＜1%)
Channel crosstalk: ≥107dB
Frequency response:
20Hz~50kHz: damping＜1.3dB
20Hz~20KHz: damping＜0.2dB
THD+N: About 0.025% (1kHz/-11.6dB@32Ω)
SNR: ≥115dB (A-weighted)
Noise floor: ＜14.1uV (A-weighted)
Dynamic range: ≥107dB
Output impedance: ＜1.5Ω
Peak output voltage: 23Vp-p

Click to expand...

Looking at the numbers, K11 R2R is definitely very competitive at its price point, definitely a class-leading performance on paper. The fully differential R2R resistor array is indeed discrete based on FiiO's photos (I dare not open my unit). There is no Bluetooth functionality, which something I rarely use anyway, so it doesn't count as a con for me.

Sound Impression as Headphone Amp/DAC​

Gears used: 64 Audio U18S, Sound Rhyme SR8, Thieaudio Monarch Mk2, Sennheiser IE600, HD660S2, HD800S, Hifiman Edition XS, HE6SE V2, Final Audio D8000 Pro LE
Music Sources: Youtube Music, Tidal Masters, Apple Music Lossless

The K11 R2R has undergone a 48-hour burn-in at a medium volume prior to the review.

Listening impression is a very subjective experience depending on individual HRTF, music library, and personal preferences, so your experience may vary.
I personally listen mostly to pop, jazz, some rock, and very limited metal.

I have to first start by saying that K11 R2R has pretty different sound signatures in NOS and OS mode. In NOS mode, it is warmish with very rounded, laid-back tonal characteristics and a smooth upper treble (maybe slightly rolled-off). In OS mode, the upper midrange details are punched up, more forward in presentation, and overall brighter signature to balance out the warmth, making the overall presentation to be more balanced.

If I have to say shortly, the OS mode is pretty much the FiiO house sound, more neutral, clinical, and leaning bright. The NOS mode, however, has more organic, smoother, and natural sounding characteristics. I will be focusing on the NOS mode from now on.

Bass is leaning on the warm side, full-bodied and natural. The subbass is very well-extended and punchy. The lower end notes have a relatively long, smooth decay, giving a certain roundness to the texture.

Going into the midrange, I find that it is relatively neutral with decent resolution. Vocals and instruments are well-layered and with a more highly-resolving transducer, you can extract a lot of details from the K11 R2R.

Treble is quite rounded off, giving a more smoothened texture overall. No sibilance, no sharpness even with brighter gears like the HD800S. I wish there would be more air, but I do have a feeling that this is by design.

Technically, the K11 R2R is quite relaxed. The standout here is the soundstage, allowing for a more nuance layering. The resolution is decent and the imaging isn’t the most crisp. However, the naturalness and organic presentation of the technicalities made up for it.

(NOS mode)
Bass: slightly warm, natural, long decay
Mids: neutral, good layering, detailed
Treble: smoothened, moderate airiness, relaxed

(OS mode)
Bass: slightly warm, crisper, faster decay
Mids: neutral, good layering, more detailed
Treble: sharper, more resolving

Power-wise, I find it pretty decent, but not spectacular. It can handle most audiophile favourites like the Sennheisers, but it falters with more demanding loads like HE6SE V2. There is also a slight hiss with very sensitive IEMs like Sound Rhyme SR8. However, I still think it's fine for a product at this price point. Alternatively, of course you can use it as a dedicated DAC for your preferred, more powerful headphone amp or speaker amp.

Sound Impression as a Dedicated DAC​

For DAC testing, the K11 R2R lineout was connected to Nobsound NS-04G speaker amplifier with a pair of 30W speakers, as well as feeding into SMSL H300 headphone amplifier. Both fixed lineout and preamp mode were tested.

Additional note: when I was using it with my earthed H300, ground loop hiss could be heard. I added the ground loop USB isolator from Topping, the HS01, and the issue went away. Note that this is not an inherent issue with the K11 R2R, but more of the RCA interconnect flaws.

As a dedicated DAC, the K11 R2R in NOS mode does carry its natural tone to the line output. With my cheap speaker setup, it does add a bit more of the lower end rumble and maybe slightly bigger soundstage. It does cut down a bit of the top end, but not so severely that you’ll lose out on details. In OS mode, the DAC performance is a pretty standard neutral DAC.

When feeding the H300 headphone amp, I find that the smoothness of K11 R2R in NOS mode to be more prominent when I compared it to my usual D300 DAC. This extra smoothness gave more of a laidback presentation and more expansive soundstage, at the cost of some detail retrieval and sharpness to the tone. H300 itself is a very neutral amp, so pairing them together is quite enjoyable.

I noticed in both lineout modes (fixed and preamp), there is a slight popping noise when switching out of the mode. The popping noise also shows up in preamp mode when there is no audio playing for a while. I have reported this matter to Fiio and I hope this is fixable in future firmware updates.

At this price point, getting the K11 R2R for pure DAC purposes is also an attractive proposition, especially for those who are looking to add R2R flavour into their setup.

Select Comparison​

Fiio K5 Pro (the original one with AK4493):
Just from first impressions, I know that the K11 line is meant to overthrow the ever-popular K5 lineup. This is especially so with the R2R version. The K11 R2R is more organic sounding, smaller footprint, and generally more usable with the LED screen, I find that it easily beats the K5 Pro in every single use case.

Cayin RU6:
I know comparing a desktop setup with a dongle might be quite a stretch, but this is the only R2R device that is the closest in price. Comparing the headphone output of both of them, I noticed that RU6 has a bit more sharpening glare in the uppermids compared to the K11 R2R. Both offer similar kinds of analogue sound signature, but K11 R2R does provide it more effortlessly and with better dynamics (unsurprisingly due to difference in power output).

Conclusion​

FiiO K11 R2R is an outstanding value product, providing a solid performance across the board in a very slim package and at reasonable price point. It's definitely here to disrupt the competition in sub-$200 all-in-one market. If you are looking for something with a different flavour from the slew of modern delta-sigma DACs in the market now, I can wholeheartedly recommend the K11 R2R.

FIIO K11 R2R
$169

Thanks to FIIO for providing the K11 R2R unit for review.
Rest assured, this review is 100% my own personal opinion.

Unboxing
Build Quality

The K11 R2R body is made from what I believe aluminum material, the FIIO logo on top is actually a RGB LED just like the OG K11, the only different part from OG K11 is that the K11 R2R has R2R logo on top of the case.

Below the K11 R2R are the same big rubber feet just like the OG K11.



Front side of the K11 you can find a 6.35mm and 4.4mm port, small screen and volume knob that double its function as a menu button.

On its back, you can find power port, usb type c port, optical in, COAX in/out, line Out.

Output Power

6.35mm rated for :

• 720mw 16ohm
• 520mw 32ohm
• 60mw 300ohm

4.4mm rated for :

• 570mw 16ohm
• 1400mw 32ohm
• 250mw 300ohm

Sound
Neutral - Warm

Bass : bass of the K11 R2R is full bodied and dense, it has that organic feeling to it, with the Oversampling mode ON, the bass is tight and speedy, with Oversampling mode OFF, it becomes more loose and has a more bouncy feeling to it.

Midrange : with Oversampling mode ON, the midrange is tilted a bit towards warm, while the Oversampling mode OFF, I feel the midrange become more organic and has even more warmth but the cost is that it doesn’t feel precise anymore, it feels again, a little more loose BUT more natural, while with Oversampling ON, the midrange feels like it digs up more resolution.

Treble : with Oversampling ON, the treble has more resolution and more resolving, and it has very good analytical capabilities, it also has superb extension and smooth feeling to it.

With Oversampling OFF, the treble again, just like its bass and midrange, felt more loose, has less resolution but gained a more organic feeling to it.

The K11 R2R feels super organic with Oversampling OFF.
Especially when paired with bright sounding IEM, it gave this particular IEM more life to it (NA2+ from NF Audio)
It also gives you the option to get more precise sounding with Oversampling ON.

Technicalities + Comparison with OG K11 & K7
Very Good for $169USD

Stage : It feels grand and more expanded compared to the OG K11.
Stage layering also feels more organic with more layers especially with Oversampling ON.
It is almost as good as the K7.

Imaging : It has superb Imaging, in fact, this is probably the strong point of the K11 R2R on its technicalities.

It can make cheap IEM such as CHU2 to feel like it sounded holographic.
So good that even I dare say that it beats FIIO own products, K7.

Separation and Positioning : Very Good.
Especially with Oversampling ON. It can show a more precise location of sounds compared to the OG K11.
While the separation and positioning is very good for its price, it still doesn't show the capabilities of a more premium offering from FIIO’s own product.

For example the K7 feels like it has more information on the separation part, like you can easily separate sound objects in more complex situations, such as gaming.

Detail Retrieval : Very Good
With Oversampling ON, it easily beats the OG K11 in terms of resolving capabilities, with Oversampling OFF, it is on par with the OG K11.


Conclusion

Is the K11 R2R recommended?

Absolutely, for $169 the K11 R2R is practically a steal.
It offers a very organic, musical sound with very good technicalities, especially the imaging department. It is so good that it trades blows with more expensive DAC-AMP products such as the FIIO K7.

Not gonna lie, I feel bad for the owner of the OG K11, the K11 R2R feels like a step up from the OG K11. I genuinely thought this product was going to be a side grade of K11, only offering R2R organic tonality on a budget price, but NO, it also offers a step up even for the technicality part, all of it with a very accessible price.

Thanks for reaching this far.

Just in case you're Indonesian or understand Bahasa Indonesia, you can watch the review here

-littlenezt.