The FiiO K9 Pro ESS review sample was kindly provided free of charge in exchange for a honest review. I didn’t receive monetary or any other kind of compensation and i don’t use affiliate links. The current price is €849 and you can order it from FiiO.eu
FiiO K9 PRO ESS
Upon reading about FiiO, one’s thoughts immediately gravitate towards earphones and portable sources. It is true that FiiO’s range of devices was predominantly smaller in size, with the exception of the K5 PRO. However, this changed recently with the introduction of their first-ever desktop DAC/amp, the K9 PRO, which boasts an internal linear power supply.Initially, the K9 PRO was released in limited quantities, as it featured the remaining AKM AK4499 DAC chips that were no longer in production due to a fire at the AKM factory. However, as time went on, the AK4499 was replaced by the ESS ES9038 PRO, giving birth to the ESS version of the K9 PRO.
It is important to note that the ESS version is not simply a replica of the original with a different DAC chip. Various adjustments have been made to the circuitry, power supply, and physical appearance of the device. These key differences can be seen in the accompanying picture.
Technical highlights
The K9 PRO ESS utilizes two ES9038 PRO DAC chips, one for each channel, to fully leverage their 8 parallel outputs in a completely balanced and differential configuration. To ensure optimal I/V conversion, low pass filtering, and driving of the THX AAA 788+ amplifiers, a total of 8 TI OPA1612 op-amps are employed, with one dedicated to each channel.At the heart of the specially designed THX AAA 788+ amplifier lies the TPA6120A2, which, thanks to its innovative design, enables the K9 PRO ESS to deliver undistorted power of 1.1W/300Ω and 2.1W/32Ω, with an impressive voltage swing of up to 26Vp-p.
The PCB layout of the K9 PRO ESS is meticulously partitioned, ensuring the separation of power supply, signals, and analog signal loop from the digital loop, effectively preventing any interference.Setting a new benchmark for FiiO, the K9 PRO ESS incorporates an internal linear power supply. This is complemented by a custom-made low-frequency transformer and four substantial 4700μF capacitors, guaranteeing an ample supply of clean power to the rest of the system.To further enhance performance, the analog and digital power supplies are isolated, and each stage of the audio circuit is equipped with its own LDO for precise voltage regulation.
For decoding USB and Bluetooth sources, dual asynchronous femtosecond clocks are employed, while automatic PLL clocks handle the decoding of optical and coaxial sources. The XMOS XU-208 digital receiver supports resolutions up to 32-bit/384kHz, DSD256, and 8x MQA unfolding.
FiiO has paid meticulous attention to the volume control, implementing an ADC curve reconstruction method that effectively minimizes any volume imbalance and noise between the left and right channels. This results in a seamless and smooth volume adjustment across all levels.
To accommodate a wide range of impedance loads, from high-sensitivity earphones to demanding full-sized headphones, a hardware gain circuit with three settings (low, medium, high) is incorporated into the K9 PRO ESS.
Wireless connectivity
The K9 PRO ESS utilizes the most up-to-date Qualcomm QC5124 chip to manage Bluetooth functions, supporting formats like LDAC, aptX HD, and aptX Adaptive. With this chip, Bluetooth connections are dependable and fast, meeting the requirements for low latency in gaming and video streaming, as well as the high bitrate needed for high-resolution audio. To enhance signal reception, an external antenna is employed. While the sound quality is excellent, it may not reach the same level as wired connections, but it is still very impressive considering the convenience and ease of use provided by the wireless connection.
FiiO Control application
The FiiO Control App offers a unique feature with its built-in Bluetooth low energy technology, which remains active at all times. This allows you to conveniently use the app even when you’re not in Bluetooth mode. With the app, you can easily choose from different low pass filters, activate the equalizer, select the input source, and personalize various other functions.
Inputs/Outputs and operation
The K9 PRO ESS is equipped with three digital inputs (coaxial, optical, and USB) located at the rear of the chassis. Additionally, it features a convenient USB type C input on the right side of the unit, allowing for easy connection with USB OTG devices.
Aside from its primary function as a combo headphone DAC/amp, the K9 PRO ESS can also be utilized solely as a DAC with either a fixed or variable output, both in balanced and unbalanced configurations. Furthermore, it can function as a standalone headphone amplifier by bypassing the internal DAC using the two analog signal inputs located at the back of the unit – one single-ended RCA and one 4.4mm balanced input.
To select the desired operation mode (headphone, pre, or fixed DAC), a switch is conveniently located on the right side of the front face. Additionally, there is a switch for gain selection (H, M, L), as well as two buttons – one for cycling through the available inputs and another for entering standby mode.During standby mode, the power consumption is as low as 1W. If you wish to completely power off the unit, you can utilize the master switch located at the back.
The chosen input is indicated by five small LEDs, while the luxurious volume control knob is surrounded by an RGB illuminated ring that changes color according to the current playing sample rate. If desired, this function can be disabled through the FiiO Control application
The FiiO K9 PRO ESS is equipped with three headphone outputs, eliminating the need for an adapter as it supports most plug types. These outputs, including a 6.35mm single ended, a 4.4mm pentacon, and a 4-pin XLR, are conveniently located on the left side of the front face. When not in use, the 4-pin XLR is protected by a plastic plug. It is important to note that the unit generates a significant amount of heat, even in standby mode, so it is advisable to place it in a well-ventilated area.
However, one drawback is that the markings indicating the various functions on the front face are barely visible, making it extremely difficult to read them, especially under direct light. FiiO has acknowledged this mistake and has attempted to rectify the issue by providing adhesive labels. Unfortunately, these labels do not aesthetically match the device and it is hoped that this issue will be resolved in future batches.
Build quality and appearance
The K9 PRO ESS is marketed as FiiO’s inaugural desktop unit, but in reality, it remains relatively compact and lightweight. With dimensions of 200x224x73mm, it can easily fit into a dedicated hifi rack or sit on your desk without taking up excessive space. What’s even better is that it comes with a custom stand that allows for vertical positioning, further minimizing its footprint. Crafted from solid, CNC-milled aluminum with a sandblasted matte black finish, the rigid chassis exudes a sense of elegance and luxury. Undoubtedly, this unit is visually stunning and well worth its price.
Accessories
The K9 PRO ESS is packaged in a rather large box that not only contains the main unit and stand, but also includes additional accessories such as the power cable, replacement fuse, USB A to B cable, Bluetooth antenna, six adhesive rubber feet, and a 6.35mm to 3.5mm headphone adapter. While the accessories package is quite extensive, considering the price point, it would be more preferable to have dedicated high-quality isolation feet directly screwed into the chassis instead of the adhesive rubber feet.
Associated gear
The K9 PRO ESS was tested both as a DAC/headphone amplifier and as a dedicated DAC connected to a 2-channel system consisting of the Kinki EX-M1 integrated amplifier and Audiophysic Step 35 speakers.
Headphone listening was done with the Focal Clear Mg, Sennheiser HD8XX, Sennheiser HD660S, Meze Audio Liric and HIFIMAN Arya Stealth plus a couple of IEMs to check the noise floor.
Power output and noise floor
The K9 PRO ESS boasts a remarkably robust headphone amplifier, effortlessly driving all my headphones with ample headroom to spare. Additionally, the noise floor remains completely imperceptible, making it an ideal companion for more sensitive earphones. While it may not be the most powerful amplifier at 2.3W for 32Ω, there are alternative models with higher power output. However, unless you possess notoriously inefficient headphones like the HiFiMan Susvara, you won’t find the K9 PRO ESS lacking in any way.
Interestingly, the single-ended output of the K9 PRO ESS shares the same power rating as the balanced output under 16Ω and 32Ω loads, eliminating the need for a balanced cable for most headphones. That being said, the balanced output offers a greater voltage swing for 300Ω loads, and since the K9 PRO ESS is a fully differential and balanced circuit, it is advisable to utilize the balanced output whenever feasible.
Listening impressions
The K9 PRO ESS, equipped with dual ES9038PRO and THX AAA technology, undoubtedly meets the expected standards of a high-quality DAC/amp. It excels in its ability to deliver a transparent and linear sound, making it one of the most impressive options available. This device remains faithful to the original source material, devoid of any coloration or imbalance. It does not impose its own character onto the sound, but rather reveals the true nature of the audio. It is highly discerning when it comes to poor quality recordings, exposing their flaws without mercy.
Therefore, it is important to note that this may not be the ideal machine for enhancing the performance of subpar headphones. However, contrary to what one might assume, the K9 PRO ESS is not excessively harsh or brutally revealing. It is not a cold, clinical tool designed solely for analytical purposes and identifying recording deficiencies. On the contrary, it has the ability to produce surprisingly musical and organic sound, provided that the source material is of good quality. In such cases, it showcases the full glory of the sound engineer’s work.
For instance, when listening to the following album, the choruses were brilliantly expanded, the instruments sounded rich and harmoniously intense, and the singers exhibited the most natural timbre with large, vivid images. The K9 PRO ESS truly brings out the best in well-crafted recordings, allowing the listener to fully appreciate the artistry and craftsmanship behind the music.
After listening to track after track and album after album, it became evident that FiiO has done an exceptional job in implementing the flagship ES9038PRO. This DAC chip, which I have encountered numerous times, stands out as one of the least digitally sounding experiences when paired with the K9 PRO ESS. The sound is devoid of any digital glare and possesses a timbre that can only be described as analogue and naturally textured. The K9 PRO ESS is incredibly resolving and intricately detailed, yet it never veers into the realm of analytical or mechanical sounding. Throughout the evaluation process, it became clear that the final tuning was meticulously done.
Those who appreciate classical music are well aware that the piano can often lose its authenticity, sounding artificial and devoid of life when played through a DAC that prioritizes technical precision over musicality. However, the K9 PRO ESS defies this trend and strikes a perfect balance between technical prowess and musical expression of the utmost caliber. When paired with Albéniz’s Iberia, this masterpiece truly comes to life, resonating with grandeur, lifelike qualities, and a harmonious saturation of rich tonal colors.
The K9 PRO ESS is absolutely fine sounding, engaging and enjoyable with all kinds of music while it has an end game technical performance and the review could have easily ended here.
If you have an interest in the detailed but often mundane tonal analysis, then you’ll find that the bass in question is rich and well-defined, exhibiting a tight and controlled quality. It also possesses impressive speed and impeccable timing, even when faced with a complex bass line. The layering is flawless, as is the dynamic contrast. However, when compared to some of its competitors, it may lack the ultimate impact and have a slightly lean and dry texture. Nevertheless, it wouldn’t be fair to make such comparisons, as achieving this level of excellence requires a significant investment in discrete designs. Ultimately, the FiiO K9 PRO ESS excels in delivering powerful dynamic swings and captivating sound contrast, leaving a lasting impression.
The mid range exhibits a slightly dry and less clear quality, yet it undeniably captivates with its final engagement and musicality. This region is skillfully portrayed, showcasing fine articulation, lifelike timbre, and an authentic sound signature, while maintaining exceptional clarity throughout.
If you have been concerned about the high-frequency performance, rest assured that FiiO has once again achieved a remarkable balance between extended range and the absence of excessive brightness, edginess, or sharpness. The FiiO K9 PRO ESS delivers a vibrant and nimble sound that flows like sparkling water, without any roughness or harshness. The overall treble response is radiant and crystalline, which may not be the ideal match for users seeking a brighter sound signature. As mentioned earlier, the FiiO K9 PRO ESS may have a slightly dry character, but it does not sound thin. There is an exceptional coherence across the entire frequency spectrum, and the notes decay naturally without sacrificing body and weight, avoiding any thinness.
The soundstage of the FiiO K9 PRO ESS is exceptional, ensuring that it does not limit the performance of your headphones. Its spaciousness, accurate imaging, and layering contribute to an immersive listening experience. However, it is important to note that while it is impressive, it may not match the grand and holographic sound of certain other discrete topologies. That being said, when paired with the Arya Stealth, one of my preferred headphones for staging, the FiiO K9 PRO ESS effectively conveys the ambiance and grandeur of expansive compositions such as Bach’s Mass in B minor.
Not only for headphones
The FiiO K9 PRO ESS excels as a standalone DAC without sacrificing performance, making it suitable for both headphone and dedicated 2-channel use. Its balanced output transforms it into a formidable DAC that can serve as the primary source in a mid-tier stereo system or be paired with active monitors and high-end headphone amplifiers. With its exceptional value to performance ratio, the FiiO K9 PRO ESS can fulfill multiple roles and serve as the central component for both headphone and speaker listening setups.
Desktop vs portable
Some of you may be curious about how the FiiO K9 PRO ESS stacks up against the more expensive FiiO M17, despite their similar specifications. While the numbers may suggest comparable performance, the truth is that the K9 PRO ESS actually has a slight advantage when it comes to listening to music.
In addition to being able to drive higher Z loads better, the K9 PRO ESS offers a fuller, more effortless, and impactful sound. It also has a somewhat grander and more holographic presentation. The timbre is more or less the same, but the K9 PRO ESS has a slightly more organic texture, smoother treble, and more liquidity in the mids.
However, it’s important to note that comparing the K9 PRO ESS to the M17 is not entirely fair. These devices have fundamental design differences and are intended to fulfill different needs. While the FiiO M17 is an exceptional portable device, it cannot surpass the performance of a well-designed desktop unit with an integrated linear power supply.
If transportability is not a priority for you and you don’t require a Digital Audio Player (DAP) that can also serve as a desktop unit, then the K9 PRO ESS would be an excellent choice for you.
In the end
The FiiO K9 PRO ESS marks a significant milestone for FiiO as their first full-sized desktop unit. With the inclusion of an internal linear power supply, this device sets off on a remarkable journey right from the start. Boasting exceptional sound performance, flawless technicalities, and a wide range of inputs/outputs, the FiiO K9 PRO ESS stands as one of the top all-in-one DAC/amps currently available. Its price to performance ratio is truly unparalleled, making it a tough competitor to beat. This remarkable debut from FiiO has left the reviewer thoroughly satisfied and eagerly anticipating what the future holds.
+ Neutral and transparent
+ Outstanding technical performance
+ Not clinical or sterile
+ Excellent as a standalone DAC
+ Multiple inputs and outputs
+ High resolution Bluetooth reception
+ Powerful headphone amplifier
+ Internal Linear Power Supply
+ App connectivity
+ Excellent build quality
+ Accessories
+ Compact
- Slightly sharp treble - A little lean and dry - Not that holographic - No remote control - No dedicated isolation feet
Leave a comment