FiiO K11 R2R DAC Review – Resistance Is Futile

FiiO K11 R2R brings a very mature and refined sound at a previously unheard-of budget price.

Introduction

Kids these days just don’t know how good they have it! Back in my day, most modern DACs sucked and you either had to use a dinosaur multibit DAC from the nineties or shell out the oligarch bucks for something like an MSB R2R. Okay, maybe it wasn’t that bad but for the longest time, true discrete R2R DACs were out of the reach of mere mortals.

I believe it was at the beginning of 2015 when an engineer by the name of Søren Kristensen presented the first DAM1021 DIY module which promised the sonic nirvana of R2R without having to mortgage an oil field.

I immediately grabbed my DAM1021 board and spent many nights relistening my musical library. The thing cost around 200EUR and you had to bring your own power and digital input stage. A buddy of mine designed the input board but I never managed to case the DAC up – my fellow DIYers will know what I’m talking about. Now FiiO has done the impossible and offers a nicely cased R2R DAC as their K11 R2R for around 160EUR. There have been other affordable R2R’s but neither have really reached greatness.

Truth be told, I was never too fond of how the original K11 sounded so read on to see whether tugging on my heartstrings with 96 precision resistors does the trick!

Specifications FiiO K11

Physical Things and Usability

Build quality

Even though I wasn’t too crazy about how the original K11 sounded, both the design and the build were an absolute highlight for me. The multi-segment LCD display activates my nostalgia neurons and the whole unit resembles a miniaturized Apple Mac mini. The main chassis is made from milled aluminum with the bottom panel serving as both the access lid and a chunky rubber foot so the K11 R2R doesn’t slip. The FiiO logo on the top can be RGB-lit by LEDs or left dark if you’re off your Monster Energy diet.

The back panel houses most of the connectors with USB-C, Toslink, and SPDIF RCA standing hungry for those audio bits and double RCA ready to spew out line-level analog audio. Power is delivered via a barrel jack. The front panel is dominated by a dark plastic piece that houses the LCD display and both the 6.35mm and 4.4mm headphone outputs. All of the control is relegated to a lone encoder knob.

In use

The FiiO K11 R2R pretty easy to set up and use. Plug in the power, an input and you’re ready to rumble! Just make sure you select the right input and output. Single click on the encoder and you can scroll through the inputs. A double click goes through headphone out, variable line-out and fixed level line-out. A longer press enters the menu where most of the options are related to configuring the LED-lit FiiO logo. The only worthwhile sound option is toggling oversampling on and off. I left it in NOS mode for most of my listening.

Under the hood

This is a good place where to freshen up our knowledge of what an audio DAC really does. In essence, it takes information encoded in a high-frequency two-level voltage and interprets it so that the output is a lower-frequency datastream with 2^16, 2^24, or 2^32 (or so they claim) voltage levels. And as we’re interested in audio, the frequency of those voltage fluctuations should fall within the audio range and maybe a bit higher to aid filtering. There are many ways how to get it done and the most common is the delta-sigma principle which is incredibly mathematically intensive and well… it works pretty well!

In our case, we’re interested in the R2R principle which is more my pay grade maths-wise. Every R2R DAC has an array of resistors where the next value is twice the size of the previous one. The DAC takes a source voltage of say +/-2V and for a 16-bit DAC the resistor array needs to be able to divide the source voltage into 2^16 equal parts, so we get the right amount of gradual voltage variants on the output. The challenge here is that the resistors have to be very precise and ought to have low thermal drift so the performance is somewhat constant. Some DACs like the venerable Lavry Gold have oven-controlled modules that keep the resistor arrays at a constant temperature.

FiiO claim that they’re using 0.1% precision resistors in the K11 R2R which is about the lowest one can afford to use to get good audio performance. After all, we’re talking about a 169EUR product here, not MSB. My DIY board from Soekris back in the day had 0.02% resistors, but I had to pay twice as much for just the DAC board. The beauty of R2R DACs is also the fact that they often can drive amplifiers without any extra IV stages and other help, so the audio path is pretty clean. The FiiO K11 R2R has two SGM8262 chips which aid with headphone amplification.

In terms of power, the K11 R2R is no slouch. It takes 12VDC from the power brick and converts it to 10 different DC voltages via converters and then uses linear regulators to clean them up. Again, some might fight me here, but I see no sense of powering the K11 R2R from a fancy linear DC supply. Most of the power supply is inside the unit and it will be what dictates the rail cleanliness. It is of course, nice to see that the K11 R2R will run nicely from a lead car battery – porta-fi freaks, take notice!

Sound quality and signature

Test setup: I mostly used the Ifi FiiO K11 R2R with the Ifi Zen CAN 3 and Topping A50 III. To better gauge the DAC’s performance ceiling, I also used it with a Feliks Audio Euforia Evo and SMSL SH-X amps.  Downstream the ThieAudio Monarch MK3, Simgot EA1000, Sennheiser HD6XX, ZMF Auteur Classic headphones were used. I used a pair of FiiO SP3 desktop speakers to evaluate its imaging performance.

First, the practicalities—the K11 R2R has a headphone output that is reasonably powerful and quiet enough for almost any IEM. I did most of my testing with it initially, and it worked fine—at least until I hooked up the K11 R2R to a dedicated amp! Both the Ifi Zen CAN 3 and Topping A50 III made me feel like I have a more direct line to that R2R sound. So, as a start the built-in headphone output is fine but I’d look to get a decent amp as fast as the budget permits.

It’s quite hard to talk about the sound of the FiiO K11 R2R if you’ve never heard an R2R DAC because the K11 R2R is the most affordable DAC that actually brings the benefits of R2R sound without the pitfalls. It’s safe to say that every digital-to-analog conversion method has its pros and cons, and the best examples try to minimize the latter and maximize the former. In other words, the K11 R2R is a decent example of what the technology is capable of and offers at an astonishing price point.

The overall timbral character of the K11 R2R is more organic than just about every DAC I’ve heard at the price point. At the same time, these characteristics are never prevalent enough to render the unit excessively colored. The midrange on the K11 R2R is to die for and there’s no trace of any sharpness in the treble regions that often haunt cheaper DACs. As for the bass, it’s very much in line with what I expect from a DAC at this level. It is controlled and decently informative.

Many of the lower-end R2R DACs tend to fall flat in terms of technicalities because of the low-quality resistors used in the array. It’s certainly not the case with the K11 R2R as it has some of the best imaging this side of 500 bucks. The sonic picture is never artificially too wide and changes organically with the recording.

Select comparisons

Topping D50 III
Topping is one of the highly measurements-led audio companies from China, with even affordable models breaking performance records. The D50 III is their middle-tier standalone DAC, which, for the first time, comes with parametric EQ capability. It also sports a Bluetooth receiver and true balanced outputs that the FiiO K11 R2R doesn’t have. The K11 R2R on the other hand has a built-in headphone driver which makes it usable without an extra amp.

Sound-wise these are very different. The Topping D50 III is extremely precise, without getting into clinical territory while the K11 R2R is very organic. Both offerings are excellent when it comes to technicalities however the K11 R2R consistently manages to render a more realistic sonic image. Topping is a no-brainer if you need PEQ, and a remote, and would like to avoid any coloration whatsoever.

Ifi Zen DAC 3
The third coming of the Zen DAC is also an all-in-one with a decent built-in headphone output. Like the FiiO K11 R2R the Ifi DAC scales well with better amplification and the built-in headphone output will be noisy with more sensitive IEMs. The FiiO is also able to receive optical and coax SPDIF signals in addition to Bluetooth.

This time both DACs are equally colored with Ifi sporting the more fun and vivid tinge to its sound which many people adore. FiiO K11 R2R on the other hand feels more natural. While the Ifi Zen DAC 3 is marginally more technically capable, I never found the edge to be impactful.

Pairing notes

I found the FiiO K11 to play very well with most gear combinations. Even more analytical amps and headphones were calmed down and showed off their technical chops with such a discerning source behind them. I’d only avoid overly warm and laid-back combos as they risk making the whole experience too sleepy.

Concluding Remarks

I think FiiO has knocked it out of the park with the K11 R2R! The sound is superb and the price is very right. The built-in headphone output is okay for getting familiar with the R2R sound and deciding whether it’s something that’s for you. For most listeners, it will be a compelling choice, and in combination with a decent solid-state amp, it will keep you up until the morning sun comes out. I can’t wait to hear what FiiO can do with this tech in even higher-end devices!

My verdict – 5/5