FiiO K13 ESS vs K13 R2R: Same Box, Two Souls. Which One Is Yours?
Same box, two souls
I heavily recommend reading my review of FiiO K13 R2R, it will fill many gaps to fully Kinderstunde this comparison: https://www.hifidaydreaming.com/post/not-the-best-in-class-not-perfect-yet-the-fiio-k13-r2r-is-my-favorite-sub-400-dac A few months ago I called the FiiO K13 R2R my favorite DAC under $400.
Not the best. Not the most detailed. My favorite. There's a difference, and that review explains why. If you haven't read it yet, start there: FiiO K13 R2R review: not best-in-class, not perfect, yet my favorite sub-$400 DAC. This piece builds on it.
Because now FiiO has done something slightly cheeky.
It took the exact same box, the same headphone amp, the same features, the same price, and swapped the heart. Out goes FiiO's own resistor ladder. In go two ESS ES9039Q2M chips. Same name, too. This one is simply the K13.
So which one should you buy?
That's the whole point of this review. Two great DACs from FiiO, one question. I'll put them head to head, talk about the sonic character of each, and then do something most comparisons can't: switch on the special modes each one hides in its menu and let them fight again.
And at the end, a little bonus about power supplies. Because of course there is.
Round one: FiiO K13 ESS vs FiiO K13 R2R
Meet the twins
Both cost the same: $319.99 for the ESS, $319 for the R2R at launch. Both come in black or silver. Both look identical apart from what you see through that round window on top.
FiiO even admits it in a footnote on its own comparison chart: apart from the differences listed, every function and interface is identical. So here's everything they share, and then everything that separates them.
What they share
Feature | Both K13 models |
USB receiver | XMOS XU316 |
Control chip | ESP32-S3 |
Headphone amp | OPA1642 + TPA6120A, fully balanced |
Balanced output (4.4mm) | 2400mW per channel @ 32Ω, 600mW @ 300Ω |
Single-ended output (6.35mm) | 1220mW per channel @ 32Ω, 150mW @ 300Ω |
Line / preamp outputs | XLR + RCA, fixed or variable |
Digital inputs | 2x USB-C (side and rear), coaxial, optical |
Bluetooth | 5.4, LDAC / AAC / SBC |
EQ | 10-band PEQ + Auto EQ (up to 24-bit/192kHz) |
Power | Internal 30W supply + 12V/2.5A DC input |
Extras | LCD, IR remote, RGB lighting, 3 gain levels, sleep timer |
Where they split
Spec | K13 ESS | K13 R2R |
DAC | 2x ESS ES9039Q2M | FiiO 24-bit R2R, 192 resistors |
Max PCM / DSD (USB) | 768kHz/32-bit, DSD512 | 384kHz/32-bit, DSD256 |
SNR | Headphone ≥121dB, line ≥125dB | Headphone ≥116dB, line ≥117dB |
Dynamic range | 121dB | 109dB |
THD+N | Headphone ≤0.00035%, line ≤0.00034% | Headphone ≤0.017%, line ≤0.019% |
Noise floor, headphone (A-wt) | SE 4.5µV, BAL 8.3µV | SE 9.4µV, BAL 18µV |
Noise floor, line out (A-wt) | BAL 3.4µV, RCA 2.2µV | BAL 7.3µV, RCA 4.3µV |
Crosstalk | SE ≥79dB, BAL ≥112dB | SE ≥77dB, BAL ≥110dB |
Sound modes | 8 digital filters | NOS / OS |
Second harmonic control | SHR, 3 levels | No |
Coaxial output | Yes (USB input only) | No |
Output modes | PO, PRE, PO+PRE, LO | PO, PRE, LO |
Specs from FiiO's official K13 vs K13 R2R comparison and the K13 product listing.
On paper, this is a blowout. The ESS has roughly half the noise, 12dB more dynamic range, and distortion lower by a factor of nearly fifty.
But you don't listen to a spec sheet. And I've been fooled by spec sheets before. So let's put some music on.
Round one, the listening: out of the box
First, the fair fight. The R2R in OS mode, which is its factory default, against the ESS with the default filter and every extra switched off. PEQ off on both, volume matched, same headphones, same CD-quality files. This is what most people will hear the day they plug it in.
Three albums. Three very different jobs.
Norah Jones, Come Away With Me: where the silence lives
This album is mostly air. A voice, a piano, an upright bass, and a lot of quiet in between. Which makes it brutal for any DAC that can't keep its background clean.
The ESS wins the silence. Between the piano notes on "Don't Know Why", the background is darker and quieter. Everything feels laid out on black, neat and clean.
But then Norah starts singing.
And the R2R simply does her voice better. Fuller, warmer, more beautiful. The ESS shows you the voice clearly. The R2R makes you care about it. On an album built entirely around one singer, that's not a small thing.
Daft Punk, Random Access Memories: order vs weight
This is one of the best-produced records of the last fifteen years. Real musicians, real studio, every instrument in its own space. It rewards a DAC that can keep things organized.
This is where the ESS really shows what a good ES9039 should do. Clean, open, forward and detailed. On "Get Lucky" the guitar, bass, drums and vocals each sit in their own lane, and you get more information about how the track was built. It pushes the whole mix into better order.
The R2R answers with weight. More bass, a thicker sound, and slightly more punch in the dynamics. The groove hits a bit harder. Less organized, more physical.
Which one is better depends on whether you listen to the production or dance to it.
Miles Davis, Kind of Blue: treble and space
Recorded in 1959, still one of the best-sounding jazz records ever made. Cymbals, horns, and a real room.
The treble goes to the ESS. Jimmy Cobb's ride cymbal on "So What" has more extension and more information, and it stays clean doing it. The ESS also places the players more precisely.
The soundstage, though? Bigger on the R2R. The room feels wider and more filled in, even if the ESS tells you more clearly who is standing where.
Round one scorecard
Category | Winner |
Background / blackness | ESS |
Treble | ESS |
Detail and clarity | ESS |
Organization of the mix | ESS |
Bass quantity and body | R2R |
Soundstage size | R2R |
Dynamics | R2R, slightly |
Vocals | R2R, clearly |
So if you made me choose between these two default settings, I'd pick the ESS.
I'm as surprised as you are. I literally wrote a review calling the R2R one of my favorite DACs.
But it isn't black and white. If you want a sound that's more forgiving, warmer, and makes vocals beautiful, the R2R is still your friend. And remember, this is the R2R with one hand tied behind its back. OS mode is not where it lives.
So what happens when we let both of them play dirty?
Round two: SHR (H2) vs NOS
Now the gloves come off. Each DAC has a special mode hidden in its menu, and both are built to do roughly the same thing: make digital sound less digital.
Before they fight, a quick explainer. Neither of these is an EQ, and neither is a normal filter.
What is SHR, or H2?
Every note you hear has harmonics, quieter tones stacked above it. The second harmonic, H2, sits exactly one octave above the note. Because an octave blends so naturally, adding a bit of H2 makes notes sound fuller and rounder. It's a big part of why tube amps and vinyl sound "warm".
ESS chips are normally tuned to remove distortion like this. FiiO's SHR (Second Harmonic Regulation) does the opposite: it deliberately adds a controlled amount of second harmonic back in, in three levels. An EQ makes some frequencies louder or quieter. SHR adds new content that follows the music, an octave above whatever is playing.
What is NOS?
NOS stands for non-oversampling. Normally a DAC upsamples the signal and runs it through a digital filter to clean up ultrasonic junk above the audible range. That's OS mode, the R2R's default, where the signal is upsampled to 384kHz first.
NOS skips all of that. The samples go straight to the resistor ladder with no digital filter at all. The result is gentler treble, softer transients and no filter ringing. It measures worse, which is probably why FiiO doesn't make it the default. It's also where most people will tell you the "real" R2R sound lives.
SHR (ESS) | NOS (R2R) | |
What it does | Adds second harmonic distortion | Removes the digital filter |
Settings | Off + 3 levels | NOS or OS |
Main effect | Thicker notes, more body | Softer treble and transients, natural flow |
Is it EQ? | No | No |
Is it a filter? | No (the ESS has 8 separate filters) | It removes one |
First impressions of SHR on its own
I'll be honest, this is one of the most fun experiments I've done on a desktop DAC.
Switch SHR on and the sound gets thicker. That added octave quietly changes how the music feels. It also makes the soundstage feel bigger and more filled in.
But that extra octave lands on everything, including the treble. Anything already a little sharp gets sharper. There's more ringing up top, more splash where you'd want less. Warmth in the middle, more edge at the top. Not exactly the trade you signed up for.
Amy Winehouse, Back to Black: the voice test
A modern record dressed as a 1960s one. A huge voice, punchy retro brass, tambourines and cymbals mixed fairly bright.
With SHR on, the ESS gets closer to the R2R than I expected. Amy's voice gains body and the whole stage swells a little. But the brass and the cymbals get edgier too, and on a record this bright you notice it.
The R2R in NOS doesn't sound like warmth was added on top. It just sounds natural. Analog, as people say, and for once the word fits. Her voice gets more chest. The bass lines have better definition. And you can play the whole album at volume without wincing.
Fleetwood Mac, Rumours: detail vs ease
On "Dreams", that steady hi-hat and John McVie's bass carry the song while Stevie Nicks floats on top.
The ESS still wins on clarity and detail, even with SHR on. You hear more of the hi-hat's texture and more of the studio around it. But that hi-hat also picks up a bit of the extra ringing SHR adds.
The R2R in NOS is the easier listen. Smoother cymbals, a better-defined bassline, and vocals with more presence and warmth. Less information, more music. Nothing changed from round one: clarity and detail to the ESS, ease, vocals and bass definition to the R2R.
So who wins round two?
Honestly, this one is a matter of taste.
SHR gets the ESS close to R2R territory. Closer than I thought a menu setting ever could. But not all the way. The R2R's smoothness comes from the way it's built, not from a switch.
But one thing separates these two DACs more than any of that.
It's not the DAC. It's what you plug it into.
The K13 R2R sounds its best in NOS. And that sound is a gift to neutral and bright speakers and amps. It makes them more musical, more approachable, and gives singers more chest.
The ESS is a different animal. It shines brightest with warmer gear around it, which makes it the trickier one to pair.
So do I like the ESS more? Yes, with my Eversolo amp.
Do I like the R2R in NOS more? Also yes, with my Rotel pre and power amps and my Dali speakers.
That sounds like a cop-out. It isn't. It's the most useful thing I can tell you about these two.
Bonus round: the DARKSIDE PRO
My full review of FiiO Darkside Pro:
https://www.hifidaydreaming.com/post/fiio-just-released-160-upgrade-for-all-of-their-devices-darkside-pro-review Both K13s hide a little secret on the back panel: a 12V DC input next to the normal AC socket, with a switch to pick between them.
Why would you bother, when there's already a decent 30W supply built in?
Because FiiO also makes the DARKSIDE PRO, a linear power supply built around a 75W toroidal transformer, for around $160. I reviewed it on the channel, and if you want the full story on how it's built and what it does, watch my DARKSIDE PRO review here.
Does it actually work with both?
Yes. The DARKSIDE PRO outputs 12V or 15V at up to 3A, and both K13 models need 12V at 2.5A, so there's headroom to spare. FiiO lists the K13 R2R as officially compatible. The ESS version is newer than that list, but it uses the identical DC input, and FiiO's own product page for it names the DARKSIDE PRO as the external supply to pair it with.
Setting it up takes ten seconds, but do it in this order:
Set the DARKSIDE PRO to 12V, not 15V, before you connect anything.
Connect the DC cable to the K13's DC input.
Flip the K13's rear AC/DC switch to DC.
Power on the DARKSIDE PRO, then the K13.
So what does it change?
On both DACs, the same thing happens.
The sound gets more composed. More open. Clearer.
And that's the nice part. It doesn't change the character of either one. The ESS is still the clean one, the R2R is still the warm one. Each simply sounds like a more put-together version of itself.
I recommend them together. If you're buying either K13 and can stretch the budget, the DARKSIDE PRO is the upgrade I'd make first.
Verdict: don't ask which is better
FiiO built the same box twice and gave it two completely different souls. Same price, same amp, same features, and yet they pull your system in opposite directions.
The ESS is the clean one. Black background, extended treble, organized and informative, exactly what a good ES9039 should be. Pair it with warmer gear and it's superb. SHR is a genuinely fun bonus that gets you part of the way toward R2R warmth, but not all the way.
The R2R is the musical one, but only once you switch it to NOS. Do that, and it makes neutral and bright systems easier to live with and gives vocals a beauty the ESS can't quite match.
So the real question isn't which DAC is better. It's what your system needs.
Your system | Buy | Setting |
Warm amp or speakers | K13 ESS | Default, SHR off or low |
Neutral or bright amp or speakers | K13 R2R | NOS, from day one |
You want detail and order above all | K13 ESS | Default |
You want vocals and long, easy sessions | K13 R2R | NOS |
And whichever one you pick, put the DARKSIDE PRO on your list.
Both are great DACs. At around $320, having to choose between two of them is the best problem you could have. To learn more and buy FiiO K13: https://www.fiio.com/k13
FiiO K13 ESS: pros and cons
✔ Clean, open, forward and detailed, with excellent organization of the mix
✔ Blacker background and better treble than the R2R
✔ SHR adds body and a bigger stage, a genuinely useful option to have
✔ Eight digital filters, coaxial output, and DSD512 support
✘ Pairing is harder: it shines with warmer gear
✘ SHR also adds edge and ringing to the treble
✘ Vocals lack the beauty and chest of the R2R
FiiO K13 R2R: pros and cons
✔ In NOS, a natural, analog sound that's easy to listen to for hours
✔ Beautiful vocals, better bass definition, more body and a bigger soundstage
✔ Makes neutral and bright systems more musical and accessible
✘ Less detail, clarity and treble extension than the ESS
✘ Higher noise floor and distortion on paper
✘ Ships in OS mode, which isn't its best: switch to NOS right away
If you enjoyed this, check out my original K13 R2R review and my DARKSIDE PRO review. Keep daydreaming.
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