Review: FiiO K11 R2R DAC/Headphone Amp

Review: FiiO K11 R2R DAC/Headphone Amp

Steve Graham wonders if a $230 resistor ladder DAC can improve a $400 streamer

 

Audio Friends

I’m storing some audio gear for a friend while he is on an extended winter escape.  With permission, I got a chance to listen to his FiiO K11 R2R.  Audio friends, just what a reviewer on a strict budget needs.  

 

R2R?

There’s a bit of a to-do, of late, about R2R ladder DACs.  I’m stretching a bit to explain this without oversimplifying it too much.  The most common way of turning a digital stream into an analogue voltage (or sometimes a current, which is then changed to a voltage) is to send it to a D to A chip that does some math programmed in at its design.  In most cases, high-speed processing (often multiples faster than the sampling rate of the data) is employed to move digitally-generated sampling noise away from the audio band.  

R2R DACs, often called ladder DACs because of their string of resistor “ladders”, use a method employed before the advent of modern DAC chips.  Discrete resistors are activated (turned on and off) by associated electronic switches corresponding to the incoming digital data.  It is claimed that this “purer” method of conversion results in better sound.  As with most things, the devil is in the details.

The resistors used in the ladder must be of a tight tolerance to ensure accurate conversion of digital data to an analogue waveform.  Typical resistors used in audio gear have a 1% tolerance, which is to say, a 1% maximum deviation from their nominal values.  Resistors with a 0.1% tolerance are available but cost more.  One of the proponents of ladder DACs claim that they machine and hand match resistors to +/- 0.025%, or better.  To maintain this level of precision the temperature must be consistent across the resistor ladder.  This is due to the physical nature of resistors, in that they change value with variations in temperature.  Discreet resistor ladders by their nature take up more real estate than a DAC chip.  Some commentators contend that temperature variations across the ladder can cause non-linearities.  I’m not saying that the K11 R2R is necessarily compromised, but there is no free lunch.  Super-precision parts won’t be found in a $200 DAC.  

 

FiiO K11 R2R

The K11 R2R is an entry into the world of R2R DACs.  At $230 Canadian, about 170 US dollars, the FiiO would appear to offer a lot for the money.  It’s also a headphone amp but I’ll only be evaluating the line-level outputs.                   

Using the Bluesound Node Nano’s digital coax output, (Review link: https://wallofsound.ca/audioreviews/digital/review-bluesound-node-nano-streaming-dac/) I connected to the FiiO with my trusty Mogami 75-ohm digital cable.  More on the Mogami later.  (Search Amazon for: enoaudio Digital Coaxial Cable Mogami 2964.)  

The knob on the front panel doubles as a volume control and gateway to various settings.  The knob is pressed and held for a few seconds to do a few things like: fixed or adjustable line outputs, headphone gain settings and of most interest to us, Non-oversampling (NOS) or Oversampling (OS) selection.  In Non-oversampling mode, data is decoded at its native rate.  When set to Oversampling all data streams are up-sampled to 384 kHz.  The K11 has an external power supply, but unlike some that appear to be no more than glorified phone chargers, the K11’s looks more like a laptop supply.  The K11 R2R is quite compact as can be seen below.  It’s roughly the same size as a Node Nano, itself the size of a 3 CD-case stack.          

 

Gimmick-Fi

Let me get this rant out of the way.  The K11’s FiiO logo on the top of the case turns various colours depending on the sampling rate of the incoming data.  This feature can be dimmed or turned off entirely.  All in all, a bit of a useless feature as the actual sampling rate is provided on the front panel display.  In my opinion, this, and other gimmicks, like VU meters, LEDs lighting-up tubes and even vaguely clockwork-like mechanisms on some amps, looks trashy and totally unnecessary.  Especially so on uber-expensive gear.  Sorry owners of Mac, ARC, Nagra and anyone else with great but trashy-looking gear.  As well, the meretricious placement to tubes, provocatively poking through the top plates of chassis, is another cheap gimmick used to seduce audiophiles.  I’m guilty of that with many of my DIY projects.  So, take my design and styling opinions with a grain of salt.     

 

Digital Connection

External DACs have an uphill battle when trying to compete with a component’s internal DAC.  Almost all digital interfaces combine clock data and music data on the same pair of conductors.  The combined clock and music data can influence each other causing loss of accuracy (distortion) in the decoded analogue output.  Connections using IIS (I squared S) data links, or other proprietary schemes that use separate paths for clocks and music data, stand a much better chance of maintaining data purity and therefore better sound.  This even applies to the lowly Raspberry Pi when a DAC board is attached, as the data transfer is in the IIS format. 

 

System

The system and the music tracks used for evaluation was the same as the Bluesound Node Nano, link above.  The only difference was that music files arrived at the Nano over Wi-Fi supplied by the music library in my NAD 50.2.  As well, the Nano was powered by a $16, 3-amp wall wart rather than its supplied 2-amper.    

 

Sound

To answer the question at the top of the article, no, the FiiO K11 R2R does not, in my estimation, sound better than the Node Nano’s analogue outputs.  That’s not to say it necessarily sounds worse.  Just different.  A sort of different that does not appeal to me, but might to other audiophiles.  Actually, this is a tale of two DACs.  Well, two DACs in one to be exact, plus a third possibility.

 

Non-oversampling (NOS) Mode

In NOS mode data is decoded at its native sampling rate.  CD-rate data especially, sounded rounded-off.  Slightly less so with higher sampling rates.  The treble frequencies sounded dulled-down somewhat, compared to the Nano’s analogue outputs.  As a result, the FiiO seemed to lack detail.  This seeming lack of detail might be the reason I found the soundstage lacking in size and specificity.  In analogue terms, it’s as if an old tube amp was in need of some new tubes or someone had inadvertently turned the treble tone control a notch or two to the left.  This presentation might appeal to someone with a lot of harsh digital recordings or zingy tweeters.  The FiiO’s bass was, by comparison to the Nano, less deep and distinct.  Though some might like this overall “vintage” presentation, it did not appeal to me.  

 

Oversampling (OS) Mode

With all files up-sampled to 384kHz, the FiiO exhibited a much different personality.  The rolled-off treble noticed in NOS mode was, in OS mode, much less so.  In fact, I’d say the treble presentation was more on par with the smooth and detailed treble of the Nano’s analogue output.  Soundstage placement and specificity was much better in OS, compared to NOS.  The improved treble highlighted the fact that the bass did not have a requisite improvement.  In fact, the bass seemed slightly worse because now it was a more noticeable shortcoming.  The FiiO just didn’t have the toe-tapping pace and rhythm of the Nano.  As well, the FiiO lacked the Nano’s bass extension, control and clarity. 

 

In summary, I’m not saying the FiiO K11 R2R is a bad DAC.  It just didn’t suit my tastes in music reproduction.  I prefer force and drive, if appropriate.  These, the FiiO lacks in both NOS and OS modes.  Sure, I like lucid midranges and filigreed treble as much as the next audiophile.  But as the man said, “It don’t mean a thing if ain’t got that swing.”  One thing to not infer, from the sonic characteristics I heard, is that it represents the general sound of all R2R DACs.  As with any component, it is best to listen and compare to a familiar piece of gear.  The FiiO was up against some stiff competition, in that the Node Nano has a very decent in-built DAC circuit.

The K11 R2R might suit some and the price to try one is not particularly high.  If waiting isn’t a problem, used ones will likely show up on the audio buy and sell sites.  

 

By way of apology

To my buddy who loaned me the FiiO, I’m sorry I couldn’t be more positive about it.  His requirements were a USB-connected DAC with a volume control so music stored on a laptop could be easily played through powered desktop speakers.  In this use, the FiiO works admirably.  In a high-end system, its performance might not be to everyone’s liking.     

 

Beg, borrow, cajole, whine, plead, connive….

That can be the life of a Wall of Sound reviewer.  It will come as no surprise that we are seldom at the top of anyone’s list when it comes to review gear.  So, we must take what comes our way and hope it interests our small but dedicated band of followers.

When a Schiit Modius E DAC, the one with the ESS DAC chip, (229 USD in black, 249 USD in silver finish) came swimming by while the FiiO and the Node where in my listening lair, I landed it without hesitation. https://www.schiit.com/products/modius  The Modius is normally powered by a 5-volt, switch-mode supply about the size of a small phone charger.  I decided an upgrade was in order so the Modius got a $16, 3-amp supply identical to the one that had improved the Nano’s performance.

I called up a few of my faithful evaluation tracks to use when comparing the Modius to the Nano.  You will, I hope, forgive me for re-using some of these from previous reviews.  They are some of my favourite music and with them I can quickly zero in on component differences.   

 

From Clannad’s Lore: Broken Pieces (16/44 file)

 

From Miles Davis Kind of Blue: So What (24/192 download)

 

And did the Modius and the Nano play well together?  They did!  There wasn’t much to choose between them in upper-midrange and treble performance.  In the vocal range, the Nano retained the small extra measure of colour (not to be confused with coloured) and intimacy that I noted in the Nano review.  The Modius was good in the vocal range but didn’t have the Nano’s small extra portion of intimacy and expressiveness.  In the bass it was slight advantage Modius.  It went a little deeper and had just a bit more toe-tapping involvement than the Nano.  Both made equally convincing soundscapes when it came to instrument and vocal placement. 

If some misguided person on one of the audio buy and sell sites is offering a Modius E, grab it quick, before he changes his mind.

 

Digital Connections, 8 bucks vs 80 bucks

(About 6 bucks versus 60 bucks in US dollars.)

I was ordering some stuff from Amazon and needed a few bucks more for free shipping.  So, I ordered a cheapo digital interconnect, (Search: Monoprice 102743 75 Ohm Digital Coaxial Audio/Video RCA Cable)

I burned it in for a few days between the Nano and the Modius.  Starting with the Mogami 75-ohm cable, I listened to the three tracks pictured above.  I then substituted the Monoprice cable.  What a difference!  At first, I thought I had accidently hit the mono button on my line stage remote.  So much of the musical presentation zoomed dead centre and was thrust forward at me.  I had, in fact, not hit the mono button.  There was some music unique to the left and right speakers but the soundstage was flattened as well and the overall presentation thrust forward.

I don’t normally solicit my wife’s opinion.  She heard what I heard but preferred having vocals and instruments more front and centre.  Go figure. 

My advice?  If you are just starting out on your journey to find a suitable DAC, spend more on the DAC and buy a cheap digital cable.  It is always easier, and more cost-effective, to upgrade the cable later. 

 

In Summary

Do I think the FiiO K11 R2R is an upgrade for the Node Nano?  No, just the opposite.  

The Schiit Modius?  More of a sideways move in my opinion.  The Modius has a lot to recommend it.  Balanced outputs, if your system will accommodate them, is one.  The Modius also has a proprietary USB input circuit, said to work better than off-the-shelf USB receivers.  If USB is your preferred connection, this might be beneficial.

The Nano’s in-built DAC circuit is very good all on its own.  Spending what a Nano costs, or less, on a partnering DAC does not make much sense and would seem, from my point of view, a waste of money.  I haven’t heard all, or even very many, DACs in this price range so if anyone has a Nano and partnered it with a DAC that improves it, please leave a comment below and be sure to tell us what digital interconnect you use.     

Anyway, digital music reproduction keeps improving and the inflation-adjusted price of admission keeps decreasing.  Win, win for all of us!  

 

Editor’s Note: Congrats to Steve on his 100th article!