FiiO K19 review: desktop DAC delivers detail in droves

There doesn't seem too much for FiiO to learn about offering value for money – almost all of its products (such as the excellent FiiO FT5 wired headphones) are 'there or thereabouts' when it comes to calculating the performance-per-spend ratio, especially at the more affordable end of the market.

But what about the less affordable end? What about – just for instance – the market for the best desktop headphone amplifiers/DACs that sell for comfortably more than four figures? Is that an area where FiiO can work its customary magic? Or is 'value for money' less tangible where products like this are concerned?

Enter the FiiO K19. It's a desktop DAC that's bigger and pricier than most – but then it's vastly better than most too, as I'll explain in this review.

FiiO K19: Price & Availability

The FiiO K19 desktop headphone amplifier/DAC is on sale now, and in the United Kingdom you'll have to spend £1249 to acquire one. In the United States it will set you back $1299, while in Australia the asking price is AU$2049.

For a product like this, at this sort of money, everyone from Chord and iFi to iBasso and TEAC has an alternative with which to tempt you. So how does FiiO differentiate itself?

FiiO K19 review: Features & What's New?

I can't decide which word is more appropriate when it comes to a discussion of the FiiO K19's feature set, so you'll have to choose. Take your pick from 'thorough', 'comprehensive' or 'exhaustive'.

The K19 keeps the majority of its physical sockets, including all of its inputs, on the rear of its die-cast unibody frame. The digital stuff is covered by USB-C, HDMI, optical and coaxial, and there's a pair of stereo RCA analogue inputs. Outputs extend to optical and coaxial, HDMI, stereo RCA and balanced XLR. There's also an RS232 on a USB-C slot, a couple of mains power inputs (DC mains adapter socket and kettle lead, accompanied by an AC/DC switch) and a 12-volt trigger loop. Wireless stuff is handled by Bluetooth with aptX HD, aptX LL and LDAC codec compatibility.

The K19 has a quad-core FPGA (field-programmable gate array) to deal with any and all incoming digital audio files. Once processing is done, the information is passed through twin I2S channels to keep signal loss to a bare minimum – and from there it's on to the DAC stage.

The FiiO uses a pair of ESS ES9039SPRO eight-channel DAC chips with fourth-gen 32bit HyperStream architecture, and this allows it to deal with PCM files of up to 32bit/768kHz resolution and DSD512. For headphone amplification there's a newly designed THX AAA 788+ eight-channel design arranged in parallel – 2x2 groups make up a balanced four-channel system. It's driven by a high-voltage power supply (8000mW + 8000mW, to be exact) that all but guarantees the K19 will drive your headphones no matter how tricky they might be.  

The digital and analogue circuits are on separate boards, and use separate power supplies. There are metal shields protecting the DSP (and ADI ADSP-21565 with SHARC+ core that's capable of 64-bit precision floating point calculations), DAC and headphone amplification – the interior of the K19 is a compartmentalised aluminium alloy isolation design. 

The upshot, in theory at least, is strong isolation, minimal crosstalk and exemplary signal integrity. And because the FiiO wears a belt as well as braces, the analogue audio circuit is ahead of a multi-stage power supply, meaning there are individual power controls for the headphone amp, DAC and every other contributing audio circuit.

What else? Well, there's low-jitter clock management. The inside of the K19 is filled with 'audiophile-grade' components supplied by the likes of Neutrik and Panasonic. There are ultra-low phase noise femtosecond crystal oscillators. And there are selectable output options – the FiiO can output from both front and back connections and be volume-adjustable, from front or rear outputs with volume control, or at a fixed level of gain from the rear sockets only.  

Actually, I have decided on the word: it's 'exhaustive'. 

FiiO K19 review: Performance

You'll make your own mind up as to whether the K19's remarkably lengthy specification is of any use to you in your day-to-day desktop audio activities, of course. But what I am prepared to say, here and now, is that you'll be impressed with the sound quality the FiiO is capable of twisting out.

And while it's obvious that putting big 24bit/192kHz files into the K19 via one of its numerous digital inputs results in more impressive sound coming out, you'll never be able to accuse the FiiO of being snobby. If you insist on putting some poverty-resolution content from Apple Music in there via Bluetooth, this desktop amp/DAC just does what it can with the tools at its disposal.

But in fact, it might just be that it's somewhere between those extremes that the K19 is at its most effective and impressive. A CD-standard 16bit/44.1kHz digital audio file incoming via its digital optical socket and out again via the 6.3mm unbalanced output to a pair of good-but-nothing-spectacular over-ear headphones is a midrange arrangement if ever there was one – but the K19 is capable of results approaching the heroic.

Its tonal balance is beautifully judged in the classic Goldilocks manner: not too warm, not too cold, but just right. The soundstage it creates is large and well-defined, and the FiiO manages the by-no-means easy trick of offering great separation along with notable focus and unity. It's alive to the finest of details, and is able to place them in proper context just as confidently as it does the broad strokes of a recording. 

Low frequencies are nicely shaped, loaded with detail regarding texture and timbre, and enjoy straight-edged attack and reasonably substantial punch without getting all showy about it. Rhythms are expressed with real positivity as a result, and momentum (in those recordings that require it) is never in doubt. Midrange reproduction is articulate and revealing, and the top of the frequency range is bright/shiny without ever veering into hard/edgy. The coherence of the frequency range from top to bottom, and the even-handed nature of its transitions, is convincing.   

There's a great deal of dynamic potency here too, both where the big changes in volume and intensity when the band hurtle into the final chorus are concerned, and when revealing the harmonic secrets of an unaccompanied piano. The overall levels of insight are profound, but the K19 seems always to serve the recording you're listening to rather than showing off about what a fabulously analytical device it's capable of being.

Move away from the desktop, up the ante where all the variables are concerned, and the FiiO is more than happy to keep pace. Connect it to some network-attached storage via its USB-C input, connect it to a power amplifier using its balanced XLR outputs, and let it have some chunky DSD256 content to deal with… and every observation I've made up to now still applies, yet somehow more so. There's more detail, greater dynamic headroom, an even more rigorous impression of staging, you name it… and consequently it proves to be a very high-quality preamplifier for a full-on system too.  

FiiO K19 review: Design & Usability

Yes, the K19 is properly built, nicely finished and relatively interesting in an aesthetic sense – but goodness, even by desktop standards there's plenty of it. At least FiiO supplies little feet (plus screws and a screwdriver to attach them) so it can stand upright – this way it's a purposeful-but-not-too-obtrusive 250 x 225 x 37mm (HxWxD). And the display on its front panel can rotate to follow its orientation.

Above the display there are a couple of dials, both with the usual FiiO light-ring around them that display a specific colour to indicate the file type and size the K19 is dealing with – one handles power and volume, the other input selection and menu navigation. Below the display are three headphone outputs – a 4.4mm balanced socket, a 6.3mm unbalanced alternative, and an XLR4 hidden behind a little plastic cover.

All of the other physical connections covered in the 'Features & What's New?' section up page are arranged on the rear panel. The other four sides of the chassis are mostly given over to heat dissipation systems – most obviously the honeycomb mesh design on the K19's two largest surfaces that allow for convection heat dissipation.

There's a quantity of thermally conductive material inside the device that's in direct contact with the electrical hardware – so heat is transferred to this material and then on to the aluminium outer frame. Yet despite all of these measures, the K19 still runs mildly warm – so it's important not to cover its sides. 

As far as usability is concerned, you get quite a few different ways to interact with the K19. The little display is, quite frankly, overburdened with menu options – they can take a good while to scroll through, and it's quite laborious to move from one submenu to another. But nevertheless, it's one method of accessing filters, updates, equaliser presets and what-have-you.

FiiO supplies a fairly humdrum remote control, which puts the major functions (input selection, volume and so on) in your hand. And then there's the FiiO Connect app, which gives you everything you might reasonably expect and almost too many customisation options.  

Chief among these is a 31-band PEQ. 'PEQ' stands for parametric EQ, and unlike the more common graphic EQ (which just allows a degree of cut or boost at specified points in the frequency range), the parametric EQ allows adjustment of the centre of the selected frequency and the sharpness of cut or boost too. It can be used directly for PCM signals of between 44.1 and 192kHz with no need for sampling rate conversion, and it's accessible on a computer via the K19's RS232/USB-C output as well as the app. PEQ presets can be shared between K19 users, too – which is nice.

FiiO K19 review: Verdict

FiiO has pushed the boat out with the K19, but as long as your desk and your bank balance are accommodating enough it's easily the best big desktop headphone amp/DAC around.

There's also every chance it's equipped to have a bigger input into the sound of your collection of digital audio files than you require, but even when left to its own devices the K19 is capable of thoroughly impressive results.

Also consider

The second version of iFi's iDSD Diablo desktop headphone amp/DAC costs as close to the same money as the FiiO K19 as makes no difference – and it's every bit as worthy of strong consideration. It doesn't have some of the operational geekery of the FiiO, but the iFi has it where it counts – which, for the avoidance of doubt, is putting a significant rocket up the sound of your digital audio files.