FiiO K5 Pro ESS Amplifier Review: A successful “forced” upgrade


In 2021, if you want to say which industry is the worst, it should be those industries that use chips as key components of products. Chip-related issues such as rising car prices, graphics card prices, and out-of-stock electronic products will all happen in 2021.

FiiO K5 Pro is a star product in the HiFi market. Because of its high cost performance, the market performance of this amp is very hot, and it is often out of stock. However, a fire in the AKM factory in October 2020 made the DAC chip AK4493 originally used by FiiO K5 Pro not available, and the supply of the product was cut off. Therefore, manufacturers have to choose ES9038Q2M, which is widely used in more professional products, as the new DAC chip of K5 Pro. So far, the FiiO K5 Pro ESS version is here.

Unboxing: Changed but not changed (Design & Configuration)

Compared to those bulky products, the FiiO K5 Pro ESS is definitely not a “big guy”. Since this desktop decoding amp uses a 15V/1.5A external power supply solution, the dimensions are only: 120×146.5×55mm, which is slightly larger than a miniature Oxford dictionary. The small FiiO K5 Pro ESS is placed on the table or next to the computer, it will not occupy too much space on the desktop at all, and you can even ignore its existence. FiiO K5 Pro ESS uses an all-aluminum alloy body with anodizing and sandblasting processes. The overall workmanship is pretty good. There are no sharp edges around the fuselage, the matte metal fuselage gives a very cold feeling, and the overall feel is very delicate.

FiiO K5 Pro ESS

In the center of the front panel of FiiO K5 Pro ESS is a huge one-piece punched volume adjustment knob and switch knob. This knob has moderate adjustment resistance, and the sound of “Da” when the machine is turned on and off is very textured, which also proves from a certain angle that FiiO’s craftsmanship is becoming more and more mature. The entire volume adjustment knob is surrounded by a circle of RGB lights, which is also FiiO’s consistent family design style. This circle of RGB lights will intuitively inform the user of the current sampling rate of the audio source through different colors. 48k and below will be bright blue, 48k and above will be bright yellow, and DSD will be green. This ingenious detail design truly achieves a high degree of unity of visual and auditory experience.

FiiO K5 Pro ESS

On the left side of the adjustment knob on the front of the fuselage are two metal adjustment levers, of which the leftmost lever is to switch the input mode, including: USB DAC, SPDIF IN and LINE IN. The other is the adjustment switch of the three-gear gain (low 0dB, medium +6dB, high +10dB). On the far right side of the front panel is a 6.3mm headphone interface. Although the FiiO K5 Pro ESS does not have an independent 3.5mm output interface, it is fortunate that there is a 3.5mm to 6.3mm adapter in the accessory, which is convenient for users to connect the 3.5mm interface headphone to this decoding amp.

FiiO K5 Pro ESS

The rear of the fuselage of the FiiO K5 Pro ESS may be regarded as the biggest change in appearance of this “forced” revision. Compared with the previous version, the logos of ESS and SABER HiFi are added on the right side of the back cover, and there are no other changes in appearance. The interfaces of this product are also concentrated on the rear of the fuselage, including: coaxial input, optical input, RCA line output/input, USB-B input interface and a power interface. In a word, the interface of FiiO K5 Pro ESS is very rich, which can well cover common audio sources including mobile phones and PCs on the market, and can also be used to drive various headphones and active speakers, with high playability. It is a pity that the FiiO K5 Pro ESS does not use the more mainstream Type-C, but uses a USB Type-B interface. Fortunately, there is a USB-A to USB-B data cable in the accessories, so there is no need to buy it separately later.

FiiO K5 Pro ESS

The hardware aspect is the biggest change in the FiiO K5 Pro ESS. The DAC chip has been replaced from the previous AK4493 to the ES9038Q2M, the flagship model of ESS in the field of portable applications. Compared with the previous generation DAC, the performance of the new chip is better, the distortion is reduced by 50%, the LO sound transmission attenuation is increased by more than 6dB, the separation is better, and the dynamic range is increased by 3dB. And equipped with XMOS XUF208 USB decoder chip and collocation clock matching management system, FiiO K5 Pro ESS supports 768k sampling rate and DSD512 hardware solution.

The amp chip on the FiiO K5 Pro ESS is still the combination of TPA6120+OPA1642 op amp, and inherits the unique technology of FiiO AM5 module. The output impedance of 10Ω is as low as 1.5Ω or less, the output power of 32Ω load reaches 1.5w, and it can output a swing of 20Vpp under the impedance of 300Ω, which truly realizes that any headphones can be easily driven.

FiiO K5 Pro ESS

Actual Listening Performance

Connect FiiO K5 Pro ESS to my laptop as a desktop USB sound card. The headphone of collocation is Beyerdynamic DT900 PRO X monitor headphones. I think most users of this product will use this scenario, so the sound performance of this review is based on the above collocation, which will be more informative. The first time you listen to it, you can feel that the FiiO K5 Pro ESS has a very typical FiiO sound style. The overall sound is loose and neutral, very similar to the sound tendencies of FiiO players. The sound of this product is more balanced, but it will be slightly biased towards the middle and bottom plates.

FiiO K5 Pro ESS

In terms of tri-frequency, the high frequency processing of FiiO K5 Pro ESS is in place, and it has a smooth and very pleasant listening feeling. The burrs of the sound are polished very smoothly, and there is not much emphasis on the treble part, so basically there is no fault. The mid-frequency is very stretched, the density of the sound is tighter, and there are some milder and sweeter colorings, which are very suitable for performing some female voices and instrumental music. The low frequency performance of FiiO K5 Pro ESS is still good, the quantity is moderate, and the downward extension can also have a certain depth, and the rebound will be slightly faster. FiiO K5 Pro ESS tri-band outlines a very harmonious sense of music. Although it is not the stunning feeling that some people like, I think this feeling will be more durable.

FiiO K5 Pro ESS

In terms of sound resolution, detail processing, sound separation, etc., the performance of FiiO K5 Pro ESS is also very good, all at the upper level of this price range. During my experience in the past few days, in the test tracks, I may prefer the sound of FiiO K5 Pro ESS playing some small-scale classical music rather than large-scale classical music. Moreover, the headphone of collocation can also have different changes, and the space is limited, so I will not discuss it here. Friends who want to experience can buy one and explore by themselves. In general, the sound performance of the FiiO K5 Pro ESS should be a very competitive player in this price range.


A fire in the AKM factory last year cut off the supply of the DAC chips used in the FiiO K5 Pro. The manufacturer had to upgrade the product and replace the ESS chip. In my opinion, this “forced” upgrade of FiiO K5 Pro is definitely a success. Not only the performance of the product has been increased, but the details of the workmanship of the FiiO K5 Pro ESS have also been improved a lot compared to the previous products. Although the price of the new product has also increased due to the change of the DAC chip, the price/performance ratio of the FiiO K5 Pro ESS is still very high. Some friends who plan to start contacting desktop HiFi may wish to buy one to play, it can give you some unexpected surprises.

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