FiiO K11 R2R
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:
Front View | |
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Back view | |
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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:
Note: At the end of the video you can see you can also quick inputs quickly with a single click on the volume rather than a long press which activated the full configuration menu.
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:
Feature | Specification |
---|---|
Name/Model | K11 R2R |
SoC | GD32F303RE |
DAC | FIIO-developed R2R DAC, USB decoding: SA9312L |
*AMP: | SGM8262-2*2 |
Weight | About 420g |
Dimensions | 147x133x32.3mm (including feet) |
Gain | L/M/H Adaptive impedance |
Oversampling Setting | OS/NOS |
Max Supported Sampling Rate | 384kHz-32bit/DSD256 (USB DAC) |
Ports and Controls | USB Type-C, RCA Line-out, Optical in, RCA Coaxial in/out, 4.4mm Balanced out, 6.35mm Headphone out |
Line out:
Feature | Specification |
---|---|
THD+N (Line-out) | About 0.025% (1kHz/0dB@10KΩ) |
SNR (Line-out) | ≥115dB (A-weighted) |
Line Output Level | 2.7Vrms |
SE output:
Feature | Specification |
---|---|
THD+N (6.35mm) | About 0.025% (1kHz/0dB@32Ω) |
SNR (6.35mm) | ≥115dB (A-weighted) |
Noise Floor (6.35mm) | <7.2uV (A-weighted) |
Channel Crosstalk (6.35mm) | ≥72dB |
Frequency Response (6.35mm) | 20Hz |
Output Impedance (6.35mm) | <1Ω |
Peak Output Voltage (6.35mm) | 11Vp-p |
Balanced Output:
Feature | Specification |
---|---|
Output Power (4.4mm, OS mode) | L+R≥520mW+520mW (16Ω, THD+N<1%), L+R≥1300mW+1300mW (32Ω, THD+N<1%), L+R≥220mW+220mW (300Ω, THD+N<1%) |
THD+N (4.4mm) | About 0.025% (1kHz/-11.6dB@32Ω) |
SNR (4.4mm) | ≥115dB (A-weighted) |
Noise Floor (4.4mm) | <14.1uV (A-weighted) |
Channel Crosstalk (4.4mm) | ≥107dB |
Frequency Response (4.4mm) | 20Hz |
Output Impedance (4.4mm) | <1.5Ω |
Peak Output Voltage (4.4mm) | 23Vp-p |
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.
Output Power Specification | K11 R2R | K11 |
---|---|---|
6.35mm Output (16Ω) | ≥660mW + 660mW (THD+N<1%) | ≥720mW + 720mW (THD+N<1%) |
6.35mm Output (32Ω) | ≥460mW + 460mW (THD+N<1%) | ≥520mW + 520mW (THD+N<1%) |
6.35mm Output (300Ω) | ≥50mW + 50mW (THD+N<1%) | ≥60mW + 60mW (THD+N<1%) |
4.4mm Balanced Output (16Ω) | ≥520mW + 520mW (THD+N<1%) | ≥570mW + 570mW (THD+N<1%) |
4.4mm Balanced Output (32Ω) | ≥1300mW + 1300mW (THD+N<1%) | ≥1400mW + 1400mW (THD+N<1%) |
4.4mm Balanced Output (300Ω) | ≥220mW + 220mW (THD+N<1%) | ≥250mW + 250mW (THD+N<1%) |
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.
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.