For our review today, we have a comparison of the FiiO K9 Pro ESS and the K5 Pro ESS, 2 of FiiO’s best desktop DAC and headphone amplifiers.
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Note, that although this shoot-out follows our latest scoring guidelines we have inserted the final scores from their previous reviews. Unfortunately, our software will automatically output a final score so feel free to ignore that.
In the past few weeks, we have had something special brewing, a shootout between FiiO’s latest iteration of desktop decoder & amplifiers, the FiiO K9 Pro ESS and K5 Pro ESS.
With both products housing Sabre chipsets, we will be revisiting their performance, features, synergy with other gears, and how they fare against each other.
A brief recap if you can’t remember the key features of the K9 Pro ESS from Marcus’s full review, the flagship DAC & amp uses dual ES9038PRO for its full balanced architecture, and it is one of the most feature-rich, all-in-one desktop solutions up to date.
FiiO has put together premium features including app control, linear power supplies, DSD256 and MQA support, THX AAA788+ amping technology, LDAC connectivity over Bluetooth, also plenty of audiophile components for this DAC & amplifier.
With a much more compact profile that could fit on any desk, the single-ended K5 Pro ESS shrinks down the size and functionality to just decoding and amping, packing in a higher native DSD512 decoding support powered by ESS9038Q2M and XMOS solution.
The amplifying circuitry uses OPA1642, also TPA6120 for the current drive, and is able to output as much as 1.5W. That is quite powerful for a small desktop device and it could drive high impedance IEMs, also common headphones like the HD650, and the DT880 Pro without a sweat.
The architecture on the K9 Pro ESS is a lot more sophisticated with much stronger amplification power, especially with balanced headphones. The 8-channel DAC chip, THX amplification as well as the high-quality power supply also gives it an edge on output power and sound performance.
Looking at just the single-ended output performance numbers on the USB Audio connection, the K5 Pro ESS can output as high as 1.5W with 32Ω load, achieving ≥118dB SNR, ＜0.0009% THD+N and 6.4Vrms output level. This is sufficient to drive sensitive cans loud with responsive bass punches, and the SNR also distortion levels are very good for the price.
The K9 Pro ESS under the same setting measures 2.1W, ≥129dB SNR, ＜0.00033% THD+N, and 26Vrms max output, which is quite a bit higher and much enhanced in distortion control.
On its balanced output, the SNR is not as high but the output power is doubled to 52V max. Despite this fact, the balanced LO enjoys ≥128dB SNR and＜0.00025% THD+N which are excellent.
There is an obvious physical distinction between the two devices. The K5 Pro ESS takes a minimalistic approach and uses toggle switches for input and gain, and it is definitely among the most well-built device at its price bracket.
The thick aluminum housing is rugged so you can stack other items on top of it providing a stealthy and modern look on the desk. The design approach is effective and there is no real physical barrier to using this device in small spaces.
The K9 Pro ESS opts for a much sharper outline, demonstrating a different set of aesthetics similar to the polygonal “Sci-fi design” on the M11 Plus. A big, centered knob with brilliant gold accents and a ring of LED sits in the middle, giving it an aggressive ‘mech’ look.
There is also a row of LED indicators displaying the status for all functions, which is informative and adds to the visual appeal.
When putting them together the K9 Pro ESS feels roughly 50% larger in volume but it comes with a vertical stand, that makes it arguably almost as good as space-saving as the K5 Pro ESS.
Both devices feature standard RCA inputs and outputs so that you could hook up to other sources or active speakers. In case you are looking for a pre-amp, the K9 Pro ESS offers better performance and loudness with its stronger output at 2.5V RMS in SE LO and 5Vrms in balanced LO, compared to the K5 that has 2Vrms for its SE LO, which is 25% less powerful.
The analog input options for using the device as an amplifier are also enriched on the K9 Pro ESS, where you will find a 4.4mm jack that could link directly to a 4.4mm balanced output of balanced portable decoders like the Hifiman HM1000 or DAPs like M11 Plus or the M17.
Some DAPs support coaxial output and using this connection both FiiO units are colored slightly warmer and more rounded sounding. If you want a tad bit of warmth added to the setup you may try this connection method instead of USB.
On the K9 Pro ESS, you will also find an extra USB-C port on the side allowing you to connect it for OT digital audio output from Android compliant devices. This is a very handy feature with decent output quality but you will need a convertor to hook up your phones or DAPs to the K5 Pro ESS.
It won’t take you more than a minute to figure out how to connect and control the K5 Pro ESS. The toggle switch allows users to switch between the different gain levels with ease. I like the no-frills experience and it is very friendly for newcomers to the hobby.
On the K9 Pro ESS, there are a lot more options to play around and it is the most advanced desktop DAC & amplifier I have seen so far in terms of software controls.
Aside from the switches on top of the panel, users could make use of the FiiO controller app to select in/output devices, select digital filters, channel balance, sleep timer, etc. There is a lot more to tweak and fine-tune on the K9 Pro ESS compared to its smaller sibling, but the changes will be reflected in real-time in the output.
The K9 Pro ESS is a step up for supporting wireless connections and is powered by the QCC5124 Bluetooth chipsets. Up to LDAC and aptX Adaptive codecs are supported with the priority of the codec for wireless playback set using the FiiO Control app.
The output with a Bluetooth connection has slightly more edges in the vocal and less fullness in the mid-lows when testing with an LDAC connection. However, it is still very enjoyable and has a good sense of control even when playing Paganini pieces.
The stock antenna is linked by SMA connectors which means you could install other aftermarket antennas of higher gain to enhance its receiving power.
For K5 Pro ESS users, it is also handy to give it a wireless upgrade by linking up to the BTA30 Pro which offers almost the same functionalities as its bigger sibling. You can also make use of its transmitter function to connect to your wireless cans, we well as use its app control panel for sound tweaks.
Although technically both K9 Pro ESS and K5 Pro ESS support USB connection, in practice the K9 Pro ESS is much more friendly with mobile devices. If you already have a phone, or a DAP you would like to use as a digital turntable, you could easily hook them up via the USB-C port on the side of the K9 Pro ESS.
On USB connection, the K9 Pro ESS has stronger decoding performance, especially in terms of separation and openness in staging. The K5 Pro ESS on the other hand performs satisfactorily for the price, and the RCA inputs allow connection to other decoders for better performance.
Both desktop units show a similarly neutral, perhaps slightly cool tone, especially on the K9 Pro ESS, though they exhibit some fun differences when pairing with different gears.
In most cases, both devices sound neutral, clean, and dynamic. The K9 Pro ESS is technically stronger in output power, resolution, bass texture, and control over the treble frequencies.
The K5 Pro ESS uses the traditional OP+BUF configuration to handle amplification. It also employs OPA1642 and TPA6120 opamps which are also used on Sennheiser’s HDV820 amplifier.
The output is clean, fast, and powerful, also slightly V-shaped such that it favors pairing with colored tunings like on the HD600, or dynamic IEMs that are mid centric, which requires the swing and cleanliness to sound balanced.
For me, it sounds very neutral and open with the upper mids being well defined, it can be paired with any items without sounding veiled or harsh.
The K9 Pro ESS on the other hand is as neutral but more powerful, dynamic, and textured with its balanced output. There is more raw energy in the output and a fast bass decay such that it favors pairing with gears that are more mid-centric or elaborated in the mid-lows.
The level of control and smooth articulation allows cleaner pairings to sound euphonic and in such regard, it is more flexible than the K5 Pro ESS.
The 6.35mm output on K9 Pro ESS sounds flatter with sensitive loads and its lead over the K5 Pro ESS is not as apparent. If you are using studio cans with 6.3mm output only, the K5 Pro ESS gets quite close in this regard but the transients and detail retrieval power are still audibly stronger on the K9 Pro ESS.
Staging & Dynamics
Compared to the AKM releases, the ESS iterations shift the focus more to the overall balance and swiftness. Both the FiiO desktop amp/DACs sound very spacious and resolving with plenty of power in the highs and lows. The K9 Pro ESS is in particularly expanded with a strong sense of instrument separation and transients in the upper mids.
When listening to the K5 Pro ESS which has a lot of power for its size, the bass, and upper mids are well energized to offer sharper transients, this works very well with weak voices and instruments that require the power to cut through. The slightly V-shaped tuning pressing down the thickness of the mids also allows more room for other elements and instruments to be heard.
The K9 Pro ESS takes a similar tuning approach but with even stronger technicalities and a more complete, expanded stage. The mid-lows are rather neutral compared to many products in the market that sounds thicker, though there is enough weight and density to image the vocalist stereophonically and distinctively.
The tuning allows more instruments to be heard instead of focusing on the strong beats or vocals. The listener can focus easily on any part of the frequency spectrum similar to some monitoring speakers but being more musical.