Setup, Customization, and Performance

Desktop Setup

Given the FiiO K19 is a DAC/headphone amp/preamp all-in-one unit, the number of wires that go in the back and front is fully dependent on how you plan on using it. I suspect most readers of this review will be using it primarily as a USB DAC for input, although the other inputs can be quite handy with non-desktop sources, such as a CD player, a phono stage, or even a TV. I ended up using the USB DAC functionality paired with my desktop PC which means using the provided USB cable in addition to the power cable/external power supply itself. The integrated Bluetooth antenna means you can also easily pair this with your phone, for example, and you can also use a longer power cable if the default one does not work out well. The stand accessory provided in the box enables using the FiiO K19 in a vertical orientation too, although note that can apply some downward pressure from cables and the K19 is not the heaviest thing either. I would go vertical with just the USB and power cables although if I had thicker, heavier cables for RCA/XLR outputs too then I might re-consider. The vertical positioning provides easier access to the knobs on the front and can also help better manage the headphone cables on the bottom.

]
Turn on the switch on the back and the K19 enters a standby mode. You will then have to press and hold the power button associated with the top wheel on the front until the indicator LEDs around both wheels light up as does the screen itself. These light rings are not just for bling as they help signal the audio playback sampling rate and/or Bluetooth codec in use, with the user guide telling you what the specific colors do. Then there's the screen itself which is going to be a big part of the user experience of the K19, be it with the onboard controls or the provided remote control. It's a good thing then that the screen, which defaults to a vertical position, can be rotated 90/180/270° allowing you to view and use it no matter how you position the K19. It's quite bright and also shows the current playback conditions such as volume, active input and output modes etc., but I do wish it was slightly larger, since the K19 is more likely to be placed further away from you than a portable DAC/amp such as the FiiO Q7/Q15 with the same screen would be.


There is a lot on offer with the built-in menu on the K19 which you can access and configure easily. In fact, you will be prompted to choose the operating language the very first time you turn on the device, although this can be changed later as well. There are also shortcuts to toggle through the inputs even without accessing the menu, which can be handy if you have multiple devices connected to the K19. The EQ section is highly relevant as the K19 has several EQ presets already saved onboard and an additional 10 custom profiles you can create and save on the K19 too. This allows you to have specific EQ profiles for different headphones too. There are five gain levels to choose from with high being the default setting, thus allowing you to have the output power stage be better suited for more sensitive IEMs or much harder to drive headphones while maintaining a useful range of volume control. We also get the default ESS filters, should you wish to play with them, as well as a bunch of other self-explanatory useful options as seen in the GIFs above.


Using the FiiO K19 with Windows 10 or 11 doesn't require any additional drivers, with Windows recognizing the device automatically. We see that the default firmware provides PCM playback options up to 32-bit, 384 kHz in addition to DSD512. The USB decoder comes in handy here, and all your favorite players will recognize the device in WASAPI (Windows Audio Session API) mode accordingly. There should be equivalent drivers pre-configured in newer macOS builds too, but I am not familiar enough to speak on this front.


If you have a device that doesn't accept UAC 2.0, or even if you simply want to try other options, then the FiiO USB audio device drivers will be of interest to you. You can find the installer on this page and the latest version at the time of testing was v5.62.0. Installation is trivial as seen above, and these drivers now allow you to make the most of the FiiO K19 within the Windows operating system.



Installing the drivers creates a new output device in Windows as well as provides access to the FiiO USB Audio Control Panel. Just be sure to set the format to your desired level and choose the ASIO (Audio Stream Input/Output) buffer size that suits your latency requirements. With that done, go to your media player of choice. I demonstrated above with JRiver again and set the audio player to the same output. At this point, you can implement further tweaks, but those are player dependent. These drivers also provide 24-bit playback support for those who find it useful. The drivers are also recognized by Roon, which is quite possibly the best thing you could have if you tend to go with local storage of music files over streaming. I have more or less replaced JRiver with Roon now for its various features and, If you are interested to give it a try, you can use this link to get a free 30-day trial (I don't get anything out of it).



The FiiO K19 is very easy to pair with your phone or other Bluetooth sources too, with the Qualcomm SoC providing decent codec support in the form of AAC/SBC/aptX/aptX LL/aptX HD/aptX Adaptive/LDAC. It is also supported by the FiiO Control mobile app available for both Android and iOS. I've used it in conjunction with the FiiO Music app on my phone for a good user experience. Adding the K19 is simple enough given the app detects it immediately, and now we have easy options including a highly useful 31-band PEQ with different profiles—which are saved onboard as seen above—as well as other features such as selecting the low pass filter, input source, Bluetooth codec, and even updating the device firmware. I will however complain to FiiO here since it claims to provide full PEQ but we only have a choice of three filter types. This is still a massive improvement over how it was before when it was just a graphical EQ though! Note that the app is also the only way to turn off the indicator lights if they bother you, I would have liked to see this be a menu option on the device itself.


The user guide mentioned support for a desktop-based DSP software engine and I had to get the installer directly from FiiO at the time of testing since the K19 had only just been announced at the time. The installer has been made available online since and seen above is the Windows version which makes it really easy to create, edit, and save various EQ profiles courtesy the 31-band PEQ functionality onboard. This is the way to go for desktop users—note that you will need to connect the RS232 port also—as the app, while user-friendly, is not as convenient. The DSP engine also has more options which go beyond just EQ, and I've asked FiiO to create a tutorial video/document to help users make the most of the hardware and software specifically made for the K19. I also expect to see this trickle down into other FiiO devices over time and this helps set a new standard for features expected in a more affordable price range too. Being able to save the profiles directly on the K19 helps differentiate it from just software-based EQ using programs such as Equalizer APO since now you can just select the desired EQ profile on the device and call it a day!

Audio Performance

Now that we have gone through the capabilities and set up of the FiiO K19, let's talk more about its capabilities in terms of driving headphones. The K19 has an output impedance <0.6 Ω, which makes it suitable for pretty much everything including ultra-low impedance IEMs, and it can provide up to 4 W @16 Ω, 2.3 W @32 Ω, and ~270 mW @300 Ω per channel off the 1/4" jack, with the equivalent numbers being 4 W @16 Ω, 8 W @32 Ω, and 1.1 W @300 Ω per channel for the balanced outputs. Note that these are the max power ratings in the super high gain mode so you can of course turn things down in lower gain settings. I had no issues using the K19 with just the single-ended output for even higher impedance headphones such as the FiiO FT3 as well as IEMs that are typically easier to drive, with the FiiO FX15 seen in the photos above as an example. In fact, I really had no need to go balanced at all, even for something like the HIFIMAN Susvara, for my typical listening levels, although I can see people opting for the balanced outputs anyway, as demonstrated with the FiiO FT5 above, for some more demanding planar magnetic headphones. Regardless, the best way to go about it is start off with low gain and work your way up only as needed to ensure you don't damage your ears or connected devices while also having a larger range of volume control. You can use the K19 vertically or horizontally as desired too, with FiiO providing feet for either option. I do think the vertical setup is how the company envisions most people using the K19 given the better quality accessories, including the headphones stand, for this orientation.


I spent a couple of weeks using the FiiO K19 with a variety of headphones and IEMs to fully test how it sounds, knowing already that it goes low enough to not have sensitive IEMs hiss and also has enough juice for demanding headphones too. The line out features worked very well and I have no complaints on that front having used this with some active speakers. I did not notice any coloring of the sound signature, and measured it to be sure. Indeed, this was the flattest measuring FiiO source I've tested to date. It seems clear that the company has taken its experience with the ES9038PRO and made a good start with the newer ES9039PRO that inherently does not sound as sterile or "bright" as the predecessor did to some people. FiiO is also the only company I know which has managed to get the THX AAA 788+ amp to not sound completely dead, and the same continues here with the K19. As such, the K19 does enough to please those who care less about source measurements and more about chain synergy too.