The hardware configuration of FiiO K9 Pro ESS is high enough, and the user experience is also excellent enough. All in all I have a hard time believing this is a desktop headset amp for only $850. After all, similar products on the market, even not as good as K9 Pro ESS, are priced at more than $1000. In my opinion, FiiO is really like Xiaomi in the HiFi circle, making it easier for consumers to contact HiFi devices at a more affordable price, so that they can enjoy different fun.

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Familiar Appearance Design

In fact, I have also experienced some FiiO decoding amp products recently, such as the previous FiiO K5 Pro ESS ($200). Although this product is relatively limited in space, it is easier to use than traditional desktop decoding amps. The FiiO K9 Pro ESS to be experienced today is FiiO’s further exploration in the field of desktop audio and is aimed at more professional users. And judging from the $850 positioning, it is obvious that the FiiO K9 Pro ESS is a heavyweight player.

As for why I say that the FiiO K9 Pro ESS gives me a very familiar feeling, not unfamiliar at all? The main reason is that the FiiO K9 Pro ESS is too similar to the FiiO K5 Pro that I have experienced before, but the K9 Pro seems to be an enlarged version of the K5 Pro. The FiiO K9 Pro ESS is definitely a big guy, with measurements of 200×224.5×72mm and a weight of 2.7kg. But fortunately, the placement of this product is very free and will not cause too much “threat” to the desktop space. FiiO K9 Pro ESS can be used with the official stand that comes with it to stand on the desktop. This placement makes the K9 Pro ESS look like a Desk Mini. And the wider thickness also allows this decoding amp to stand on the desktop very stably and will not shake easily.

FiiO K9 Pro ESS continues to use the square design of the previous generation product in appearance design, without extra lines and edges, it looks very low-key and restrained. The K9 Pro ESS uses a pure black all-aluminum matte body, and a heat dissipation hole is also designed separately on the side of the body. This fuselage design has good dirt resistance and is not easy to be contaminated with fingerprints. And the design of metal material and heat dissipation holes can further enhance the heat dissipation effect of the machine.

The design of the front of the fuselage is developed around a large volume knob, which is also a very recognizable design. And the knob has also changed from the previous silver to gold, in order to distinguish the ESS version from the previous AKM version. There is a circle of RGB indicator lights under the knob, which indicates the format of the current audio source through color changes. It is worth mentioning that this knob is reconstructed through the ADC curve, which effectively solves the problem of volume left and right bias and noise. The volume knob is finely adjusted without jumping, ensuring the precise adjustment of the volume.

Buttons & Interfaces

All operation buttons of FiiO K9 Pro ESS are designed on the right side of the volume knob. These include working mode switching, gain selection switch, audio source switching button and power switch button. Since this decoding amp is not equipped with a display, there is an indicator light for the input source above the button. Overall, the function buttons and indicators of FiiO K9 Pro ESS are simple and clear, and there is no cost of learning. If you are a senior enthusiast, you can also download the FIIO CONTROL APP on your mobile phone. After the machine is successfully connected to the mobile phone, you can set Bluetooth encoding, filter selection, channel balance and other functions on the APP, allowing enthusiasts to easily unlock more ways to play.

As a desktop decoding headphone amp, there is no ambiguity in the configuration of the interface. The interface of the FiiO K9 Pro ESS is quite rich. On the left side of the knob on the front of the fuselage, there are 4-pin XLR, 6.35mm single-ended and 4.4mm balanced connectors. For users who like to use the 3.5mm headphone jack, an adapter is also included in the package. This interface setting is enough to meet the basic needs of users.

In addition to these commonly used interfaces on the front, most of the interfaces of the FiiO K9 Pro ESS are designed on the back of the fuselage. Including conventional power interface, optical fiber, coaxial, Bluetooth antenna, RCA, XLR balanced output interface is readily available. In addition, there is a Type-C interface on the right side of the fuselage, which is more convenient when connecting to a mobile phone. The rich interface configuration and the working mode switch button on the front of the fuselage allow the FiiO K9 Pro ESS to be used as an audio decoder, as well as headphone amplifier and preamp work, which is enough to meet the needs of different users.

Acoustic Configuration & Sound Quality Review

Before talking about the sound performance, it is still necessary to introduce the hardware configuration of FiiO K9 Pro ESS. As with the previous FiiO K5 Pro, due to a well-known reason, the previously used AKM4499 was out of stock, so the DAC part had to be replaced with a dual ES9038PRO architecture. Apart from that, there are almost no additional differences in hardware configuration between the two versions. Whether it is AKM4499 or ES9038PRO are top DAC chips, coupled with THX AAA 788+ amp technology, dual femtosecond clocks, high-performance linear power supply system, etc., FiiO K9 Pro ESS basically has no shortcomings in hardware configuration.

I connect the FiiO K9Pro ESS to my laptop and use it as a desktop USB sound card. The matching headphone is Beyerdynamic DT700 PRO X monitor headphones equipped with STELLAR.45 units. The sound performance of this evaluation is based on the above combination, and other gameplay friends can unlock the experience by themselves.

In recent years, the sound style of FiiO products has changed. The sound of FiiO K9 Pro ESS will make me feel a little warmer, and the sound has a light and bright style, which I like very much.

In terms of high frequencies, this is probably my favorite part. There is no sense of restraint, the sound is full and not hollow, the high frequency energy is very sufficient, and it is round and translucent without feeling stimulating, which sounds very attractive.

The mid-frequency aspect will be slightly backward. In the loud field, the sound separation is very good, and it has very accurate positioning information.

In terms of low frequency, the low frequency quality of FiiO K9Pro ESS is also satisfactory. The quantity sense is relatively moderate, and it can also have a certain depth.

The sound performance of FiiO K9 Pro ESS is relatively well balanced. There is a certain sense of density in the smoothness, and a certain sense of agility and vitality can be felt. In short, the sound performance of this decoding amp is an all-round existence without obvious shortcomings. In my experience in the past few days, whether it is classical music, pop music or ACG, FiiO K9 Pro ESS can handle it very well.

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