The FiiO K9 was kindly provided free of charge in exchange for an honest review. I haven’t received monetary or any other kind of compensation and I don’t use affiliate links. The price of the FiiO K9 is $499 and you can order it from FiiO.eu.
FiiO
As usual no lengthy introductions for FiiO since there is not a single person in the audio hobby who doesn’t know about them. The brand is extensively covered by ichos-reviews and if you search for the “FiiO” tag you can read reviews for most of their products.
FiiO K9
The FiiO K9 is the little brother of their desktop, flagship DAC/amp, the FiiO K9 Pro ESS. The main difference in the audio circuitry is that the two ES9038PRO DAC chips are replaced by two ES9068AS, still in a fully balanced and differential configuration. Still common are the dual THX AAA 788+ modules which are used to handle the amplification duties, two OPA1612 for the low-pass filtering, two OPA1602 for the buffer, the NJU72315 volume IC and the QCC5124 Bluetooth chip that supports wireless reception with the LDAC, aptX HD and aptX adaptive codecs. The FiiO K9 incorporates an embedded linear power supply with a toroidal transformer and 4*4700μF of total capacitance. High quality parts and a custom made transformer are used but the K9 PRO ESS features a beefier power supply with a larger transformer and higher quality parts. The USB receiver is the newer XMOS 308, instead of the 208 that is to be found in the K9 PRO ESS, which supports 32bit/768kHz PCM & DSD512 but no MQA which is becoming obsolete. For reminders the FiiO K9 PRO ESS supports 32bit/384kHz, DSD256 and MQA.
Full technical documentation is available here
Value for money
From the technical breakdown and the connectivity options that we are going to discuss later, it becomes clear that the FiiO K9 shares a lot of common characteristics and internal parts with the flagship K9 PRO ESS but it is a whole $350 cheaper thus it is an all-in-one desktop DAC with exceptional value for money.
Connectivity and usage
Inputs and outputs to be found in the FiiO K9 are exactly the same as in the FiiO K9 PRO ESS except the side mounted USB type-C OTG port. At the front face there are the three headphone jacks (4-pin XLR, 4.4mm and 6.35mm), the volume control knob, the output and gain switches and the input selection button that also enables the mute and standby functions. Above them there is a row of five, tiny LEDs that display the selected input. The user can select between three output modes; headphones and fixed or variable line output.
The line outputs at the back panel of the unit are both stereo XLR and RCA jacks. USB, optical and coaxial digital inputs are included. The FiiO K9 also supports 4.4mm and RCA line inputs so it can be used as a standalone headphone amplifier.
The volume knob has an integrated RGB LED ring around it that changes colors according to the working status. A continuous press of the front face power button will set the unit into standby mode and for a full power off you must use the power switch at the back.
The FiiO control application
The FiiO K9 supports low energy Bluetooth mode that is constantly active and allows connectivity with the FiiO Control application even when Bluetooth reception mode is off. With the FiiO Control application you can adjust various parameters like low pass filters, status indicators, channel balance and enable the PEQ which is only effective in Bluetooth reception mode.
Appearance build quality
The FiiO K9 is almost identical looking with the K9 PRO ESS. A compart sized rectangular device with smooth edges and corners that can easily fit at your desktop. You can also place the K9 in a vertical position with the help of the included stand so you can save space. The most notable visual difference between the two units is the volume control knob which is plain black in the FiiO K9 without the golden ring at the outside perimeter. FiiO has also fixed the difficult to read, dimly painted letterings underneath the buttons and LEDs as were found in the K9 PRO ESS. Now they have a well printed and visible white color. The rigid and robust chassis is made from CNC milled aluminum with a sand-blasted matte black finish.
Accessories
The FiiO K9 comes packed in a big cardboard box and is accompanied by an AC power cable, a spare fuse, a USB cable, the Bluetooth antenna, six adhesive rubber feet, a vertical stand, and a 6.35mm to 3.5mm headphone adapter. FiiO also includes a cover for the 4-pin XLR headphone plug to conceal it when not in use.
Power output
The FiiO K9 headphone amplifier is quite powerful and capable of 2W/32Ω or 780mW/300Ω with 42Vpp of maximum voltage from the balanced output, enough juice to run most of the headphones on the market. Comparatively the FiiO K9 PRO ESS, with the beefier power supply, is slightly more powerful at 2.1W/32Ω and 1.1W/300Ω with 52Vpp of maximum output voltage.
The FiiO K9 has three gain settings to allow for better adaptability with various loads and is also suitable for high sensitivity IEMs thanks to the noise free background and the low output impedance. Something that must be noted is the somewhat strange volume curve of the potentiometer which has to be turned more than ¼ of the available range in order to start outputting sound.
Associated gear
During the evaluation of the FiiO K9 I have used various headphones like the FiiO FT3, iBasso SR3 and the Focal Clear Mg among others. The FiiO K9 was connected to the Volumio Rivo streamer. The power cord, USB and all headphone cables are made by Lavricables . As per usual practice the FiiO K9 was burned for about 100 hours before listening evaluation.
Listening impressions
Not surprisingly, the FiiO K9 sounds very close to the K9 PRO ESS and as a matter of fact it also reminds a lot of the FiiO R7 with the FiiO PL50 linear power supply. What an achievement if we consider the price difference between the K9 and the two other members of the family.
The sound is crystal clear and transparent throughout the whole frequency range with supreme linearity and neutrality. The K9 demonstrates excellent source fidelity without adding any character of its own but at the same time it is not clinical or sterile. The same applies both to the DAC and the headphone outputs of the FiiO K9 because the THX amplifier is able to pass the DAC sound output directly to your headphones without any further coloration.
The DAC and the THX amplifier stages are a combination that produces deep and well controlled bass, which may not be that full bodied and visceral but it shines with excellent control and definition. The low-end is fast and powerful with extended dynamic swings and thundering impact. An overall performance that is not that far from the K9 PRO ESS which nonetheless manages to produce weightier and not as dry bass with better control and greater dynamics.
The K9 is very resolving and defined for the category, both in the mid-range and the treble which is not devoid of some sharpness but it doesn’t sound too bright or harsh despite the presence of extra brilliance and luminosity. The K9 is not as refined or resolving as the K9 PRO ESS, not as polished either but it gets close enough and certainly up to the level of the FiiO R7 when it comes to detail retrieval. The highs on the K9 PRO ESS are also smoother and less edgy. Back to the K9, it is alive, airy and spacious with some fine articulation both in the mids and the highs.
As already discussed, the K9 is not clinical or sterile, there is plenty of engagement on offer with all kinds of music. The overall texture is lean and just a bit dry but the timbre is natural, harmonious and realistic with only a touch of artificiality in the treble. The K9 PRO ESS on the other hand is more natural and organic sounding with a slightly fuller texture and less artificiality in the treble. The FiiO K9 is pretty revealing of source material quality and while it is not ruthlessly punishing you should remember that it will expose bad quality recordings so care should be taken during matching with various headphones, especially brighter ones.
The soundstage of the K9 is wide and expanded with plenty of air around the various performers and a sharp, accurate imaging. The FiiO K9 PRO ESS can sound deeper and more holographic but the K9 is still capable of producing a relatively deep and quite grand soundstage that will open even the most claustrophobic headphones of your collection. A nice match was with the slightly warm sounding Sennheiser HD660S2 which opened up a lot and helped to tame the slightly aggressive treble of the K9, a very enjoyable combination for listening to favorite baroque pieces.
A true all-in-one audio device
The overall audio performance of the FiiO K9 is constant and of the same quality both from the headphone and the line outputs thus making it an excellent partner for headphones and powered monitors alike or even as a standalone DAC to an external amplifier. The same applies to the headphone only section of the K9, the internal amplifier bears all the above described sound characteristics and can do justice to every external source like a phono stage. Such a stable performance from all the inputs and outputs of the FiiO K9 makes it a high quality all-around audio device that can form the center of a desktop listening system. Use it as a source for digital media or listen to your favorite vinyl recordings through the line inputs, either with headphones or active speakers.
Vs the FiiO K9 PRO ESS ($849)
Everything that you would like to know is included in the main body of the review but I guess that you already knew that.
Vs the FiiO K7 BT ($249)
The FiiO K7 is an upgraded version of the much acclaimed FiiO K5 Pro ESS, that utilizes dual AKM 4493SEQ DAC chips and dual THX AAA 788+ amp modules that produce the same power output with that of the K9 at 32Ω and slightly inferior at 300Ω loads. The FiiO K7 BT uses an external power adapter so it is considerably more compact than the FiiO K9 but it is lacking many input and output options, like the headphone 4-pin XLR plug, the balanced XLR line output and the 4.4mm line input.
The FiiO K9 is double the price of the K7 and except for the extra connectivity you also buy much improved technicalities with a sound signature that is more transparent and cleaner, has tighter and considerably more dynamic bass, better layering and definition, deeper detail retrieval and a wider, more accurate soundstage. The K9 is also more resolving and refined but at the same time more revealing and less forgiving with a more aggressive treble profile. The FiiO K7 BT can’t reach the technicalities of it’s bigger brother, it is more congested and less airy but it is also warmer sounding, has a smoother treble and a more analogue approach to it’s sound signature. So, while the K9 is undoubtedly the superior performer, I can see many people preferring the FiiO K7 BT for its politeness and warmer sound character.
In the end
If you want to stay in the FiiO camp and you need a DAC/amp with more I/O options and a slightly stronger technical performance than the FiiO K7 BT but you don’t care about the superlative technicalities or you can’t afford the FiiO K9 PRO ESS then the FiiO K9 is tailor made for you. On the other hand, if you are brand agnostic and just looking for a good sounding all-in-one DAC/amp with plenty of connectivity options and a really affordable price, without compromising in performance, then the FiiO K9 is again tailor made for you.
Truly enough, the FiiO K9 combines near flagship level of audio quality with plenty of I/O options at a price so low that is hard to believe. FiiO is well known for making some of the best value audio components in the market but this time, with the FiiO K9, they have really outdone themselves.
Copyright – Petros Laskis 2023.
+ Near flagship performance + Excellent fidelity + Crystal clear and transparent + Excellent technicalities + Expansive soundstage with precise imaging + Powerful headphone amplifier + Plenty of I/O including analog inputs + Various use scenarios + Customizable through FiiO Control application + Excellent build quality + Compact sized and vertical stand + Exceptional value for money - Treble can sound a little sharp and bright - Not that full bodied - Not forgiving - No remote control - EQ is effective only in Bluetooth mode
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