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We're going hands-on with the FiiO K9 Pro ESS version, comparing it side-by-side to its predecessor
We're going hands-on with the FiiO K9 Pro ESS version, comparing it side-by-side to its predecessor IBTimes / Jeff Li

FiiO shook the audiophile world in 2021 with their release of their first high-end, desktop grade DAC/Amp - the K9 Pro. However due to the global shortage of AKM chips, for a while the K9 Pro was a rare collector's item. However, FiiO very quickly caught up in early 2022, with the re-release of the K9 Pro, this time equipped with dual ES9038PRO chips as well as some cosmetic differences.

Having featured the K9 Pro AKM version in a previous review, we had the opportunity to also spend considerable time with the new ESS version and directly compare the two. Could the 'involuntary' design result in an improvement of the original design of the K9 Pro? Or will the ESS simply be a passing phase until AKM can get their production back on track? Let's dive in to find out.


Similarities with the Original K9 Pro

Overall, the K9 Pro ESS looks nearly identical to the original AKM version. The same solid metal build, entirely matte black, with FiiO's latest signature aggressive 45 degrees chamfer that can be found on the M17 DAP as well.

Controls are also identical, with the oversized volume knob at the center, output mode toggle, gain toggle, input selector and power buttons on the right. On the left of center, there's the triple headphone outputs: balanced XLR, 4.4 mm and 3.5 mm ports.


On the rear of the K9 Pro, there is the same impressive array of input and output ports, identical to the original version. One of my favorite features of the K9 Pro design is that it has two power controls - a flip switch in the rear, and a push button in the front. The rear allows for total control of when the device is powered, but at the same time offering the convenience of turning the device off right from the front panel.


External Differences from the AKM Version

Though the two devices have a lot in common, FiiO also put enough difference between them that made sure people would not confuse the twin siblings.

First and foremost, the polished circumference of the volume knob has changed from a chrome silver tone to a mirror gold finish. Personally I prefer silver more than the gold, but I have to say the gold is a nice match to the 'Hi-Res' certification on the top of the K9 Pro, as well as the embossed 'Pro' emblem on the left-hand side.


The second major difference is the added cooling vents on the two sides of the device. While the K9 Pro AKM version has its innards completely sealed in the metal case, the openings on the ESS version reveals a glimpse of the components inside. Perhaps the addition of vents will improve the heat dissipation performance, but honestly speaking I did not see anything that needed to be improved upon with the AKM version, which never got too warm during operation.


The last difference in the K9 Pro ESS version is the introduction of the ability to stand it up on its side, which can further improve cooling by exposing more surface area of the case to open air. To stand the unit up securely, the ESS version comes with a small bracket that holds the unit vertically. FiiO have also sent the unit without its rubber feet attached, giving the user the option to decide which configuration they want the K9 Pro to be used in. The weight distribution of the DAC/Amp is surprisingly well balanced, which allows it to stand very stably in an upright position. Your coffee mug is more likely to topple before the vertical standing K9 Pro takes a tumble.


Significant Differing Sound Characteristics

The most burning question in comparing the AKM and ESS versions of the K9 Pro is obviously not the minute external differences, but rather the impact of the chipsets on the sound performance. Could the 'forced' change of DAC chip be a blessing in disguise? Since most of the components of the two versions of K9 Pro units are identical, the comparison also becomes an unintentional contrast of the DACs in themselves.

Firstly I'd like to address the soundstage as it was the most anticipated feature for me personally. On the AKM version, when paired with the right headphone (In my case it was the Sennheiser HD660S), it resulted in one of the most phenomenal staging I've heard. Since the original K9 Pro consisted only of a single AK4499EQ chip, and the ESS version has dual ES9038Pro chips - taking care of the balanced left and right channels separately - common sense dictates that the staging should be better. The result was surprisingly not as expected. After extensive A-B comparisons, I had to succumb to the conclusion that the AKM edition still won out in terms of separation and staging, especially with the HD660S. (That's not to say that the staging with the new K9 Pro is substandard, in fact when compared to the FiiO M17, it still provided a much wider soundstage.)

When it comes to other areas, like being paired with a planar headphone that's hard to open up sound like the Audeze LCD-2C, the advantage went back to the new ESS version, which has a more energetic and clinical sound compared to the AKM version. While the AKM has a warmer, rounded sound, the ESS version has a sharper, edgier and more analytical sound - which was a great match for the LCD-2C that is warmer in nature. The high-end detail that the K9 Pro ESS triumphs in was apparent when comparing it on medium gain and the AKM on high gain, the former still capturing more high end sparkle than the latter.

Since the LCD-2C is already an outstanding performer when it comes to vocal reproduction, bolstered by the ESS powered K9 Pro it produces smooth and not fatiguing airy textures that sent pleasure shivers down my spine.

Surprisingly, I find more similarities in the energetic sound characteristics in the K9 Pro ESS with the Schiit Jotunheim 2 which we recently reviewed than with the K9 Pro AKM.


Final Verdict

The global shortage of AKM DAC chips will be an event that audiophiles will be talking about for years to come, and the ripples caused by it had the unintended consequence of spawning a whole range of audio devices based on the ESS chips across the industry.

Is that a bad thing? In the case of the FiiO K9 Pro ESS version, it's a resounding 'no'. When compared directly to the AKM version, each of the K9 Pros had their own color and character and simply provided another choice for us consumers. And more choice is always good news, because as we have found, different headphones have different needs. When paired with a headphone that is warm in nature, and hard to open up like the Audeze LCD-2C, we wholeheartedly recommend the ESS version, which is definitely better.

David is a tech enthusiast/writer who is often on the move, but since the pandemic is on a mission to explore gadgets to improve his 'home work'. This is a contribution to an ongoing IBTimes review series on gadgets for Home Productivity.