FiiO K3 – Review

FiiO K3

FiiO K3

| USB Amp/DAC | AKM AK4452 DAC | XMOS XUF208 | OPA1612 LPF | 2x OPA926 | DSD256 | 320mW |

FiiO K3, a freshly released headphone amplifier and USB DAC with a tiny size, impressive specs but super affordable price.

The FiiO K3 is the latest Amplifier/USB DAC from FiiO, introduced as the upgraded successor of the ultra-famous FiiO E10K and FiiO E10.

The FiiO K3 features ADC digital volume control, dual headphone outputs with a dedicated 2.5mm balanced output, 2 USB audio modes, native DSD256 support and decoding capability of up to PCM384kHz/32 bit.

Beneath the tiny housing, the FiiO K3 holds a AK4452 DAC, a XMOS XUF208 USB chip, 2x OPA926 driver OP Amps and a TI OPA1612 low-pass filter OP AMP.

The FiiO K3 is joining the newest products of the brand, among the:

The FiiO K3 is born as an advanced update of the FiiO E10K making it sit as the flagship model over every previous one on the E10 line.

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FiiO K3 Review

Tests & Scores


Advanced Features

The FiiO K3 features include advanced options such as:

  • USB Amp/DAC: USB Amp/DAC with Type-C connector, capable of decoding up to 384kHz/32-bit – As an example, the FiiO M9 in USB DAC mode reaches 192kHz/32bit.
  • Penta output connection: standard 3.5mm headphone jack, 2.5mm TRRS balanced output, USB Type-C audio output, SPDIF.
  • Native DSD support: hardware decoding of DSD256 – In comparison the FiiO K3 vs FiiO E10, the E10 was not able to decode DSD
  • TI OPA1612 LPF
  • Dual OPA926 op-amps
  • XMOS XUF208 microcontroller: This is the same on both the FiiO K3 vs FiiO Q5



FiiO K3 weight in Ounces and FiiO K3 weight in grams.

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Accessories & Packaging

The FiiO K3 unboxing results in an USB Type-C cable (used to power the unit and to connect to any PC and Mac) and 4 anti-sliding pads that can be stuck to the bottom of the unit – Amps rarely include more accessories than the FiiO K3 does.

The unit comes inside a clean looking rectangular packaging with a design and style inline with the FiiO M3K, FiiO BTR3 and FiiO M9.

gramophone-25660  3.25/5



The FiiO K3 has curved edges and a clean looking design that gives it a classy feel.

The all-metal construction and the sandblasting process results in a pearled-black finish that adds to the clean aesthetics.

The FiiO K3 is not a standard amplifier regarding size and footprint. In fact, it is quite impressive how the brand was able to fit such an advanced and powerful amp inside the tiny housing.

To be more precise, the dimensions of the FiiO K3 are 70mm×58mm×22mm and has a total weight of only 82 grams.

On the top of the unit you will see the Hi-Res Audio certification and the FiiO logo.

FiiO K3 volume knob RGB light

The volume knob has a new RGB light that informs when the unit is powered on and also indicates the digital audio input sample rate by changing color.

  • Green= DSD format
  • Yellow= Sample rate higher than 48kHz
  • Blue= Sample rate lower than 48kHz


FiiO K3
FiiO K3


Operation & Control

The FiiO K3 has 3 switches and a physical volume knob.

The knob has a digital ADC volume control and a smooth, stepless rotational movement with enough resistance as to give it a precise volume regulation.

The 3 switches of the FiiO K3 are placed separately, 2 of them are on the front panel and the third one can be found on the back panel.

The front panel switches turn on/off the Bass Boost feature of the FiiO K3 and set the Gain (Low/High), while the rear one works a switch between USB audio modes (UAC 1.0 and UAC 2.0)

The operation and control of the FiiO K3 is quite simple and has no learning curve involved. Any user will get the FiiO K3 working right out-of-the-box without issues.


How to power the FiiO K3:

The FiiO K3 gets powered directly from the USB Type-C connector that connects to your computer, there are no additional power supply nor chargers needed for the FiiO K3.

Nonetheless, FiiO recommends to keep the power input rate on DC 5V and 500mA.

Once the unit is correctly connected to your PC or Mac, the FiiO K3 can be turned on by simply rotating the volume knob clockwise until you feel/hear a click.

To confirm that the unit is On, an RGB light placed behind and around the volume knob will turn on.


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FiiO K3 volume knob
FiiO K3 volume knob
FiiO K3 switches and connectors
FiiO K3 switches and connectors


Construction & Build

The FiiO K3 is fully built in aluminum and feels as robust and well-constructed as the FiiO BTR3, FiiO M3K and FiiO M9.

The K3 is not a device that tends to get easily scratched but to avoid any marks on the bottom of the unit, it is recommended to stick the anti-sliding pads that FiiO includes for free.

The volume knob, switches and plugs operate securely and connect firmly with no flimsy nor weak mechanical feel.


FiiO K3
FiiO K3



The FiiO K3 has a powerful (for the size) XMOS USB receiver chip – exactly the same as the FiiO Q5 Amp (flagship portable amplifier from FiiO).

The inner components of the FiiO K3 make them capable of decoding up to 384kHz/32-bit and native DSD256 – these specs are difficult to find in an amp of this dimensions and price, even the massively famous FiiO E10K could not reach this decoding level.

Moreover, the dual USB Audio modes of the FiiO K3 grant full compatibility with any PC and Mac. For devices where a driver cannot be installed or where any issue might arise with the UAC 2.0 mode, a simple switch to UAC 1.0 makes it driverless and fully working as a plug and play external DAC/Amp.


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FiiO K3 ports
FiiO K3 ports



Despite the tiny size of the FiiO K3, the unit holds a penta output connector design and a USB Type-C plug.

The 5 output connectors included are:

  • 3.5mm single-ended headphone jack
  • 2.5mm TRRS balanced out
  • Coaxial Out
  • Optical Out
  • Line Out

The output connectors of the FiiO K3, have the following technical specifications:

Coaxial-out specifications

  • RCA for 192kHz, support DSD64 DOP

Optical-out specifications

  • Up to 96kHz

3.5mm Headphone out specifications

  • 220mW(16Ω); 120mW(32Ω)

Balanced Headphone out specifications(2.5mm TRRS port)

  • 320mW(16Ω); 200mW(32Ω)


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FiiO K3 front panel
FiiO K3 front panel
FiiO K3 rear panel
FiiO K3 rear panel



The FiiO K3 has 2 Gain and 2 Bass Boost modes; the Gain modes available are Low Gain and High Gain while the Bass Boost can be completely turned off or turned on – Bass Boost can be used in either Gain mode.

As the FiiO K3 offers all these modes we decided to test it and measure it’s frequency response curve in every combination available.

While using the FiiO K3 in Low Gain and with Bass Boost turned off, the amp showed a clean sound with no coloration nor degradation.

Our FiiO K3 frequency response graphs also showed a flat response with no boosting nor recessing on any audio frequency.

The new ADC digital volume control of the FiiO K3 revealed a very accurate and precise sensitivity to the knob regulation.

In addition to this, the amp did not present any channel imbalance while controlling the volume nor any of the typical “scratching” noises of devices with analogue potentiometers.


FiiO K3 Bass Boost tests

One of the 2 front switches of the FiiO K3 enables/disables the Bass Boost function.

According to FiiO, Bass Boost on the FiiO K3 should provide +6dB of boosting over most common bass audio frequencies.

Despite the brand’s statement, we decided to test and measure the Bass Boost performance and our FiiO K3 frequency response measurements verified that, indeed, it provides +6dB on the most efficient boosting range and starts to gradually cut-off above 125Hz to keep the sound clean and clear.

Of course, this pronounced bass boosting will modify the sound personality making it switch from an Amp/DAC with a flat response into a bassy, warm and vigorous one. Nonetheless, FiiO has not exaggerated here, introducing the right amount as to add energy and fun to any headphones sound signature without killing off the baseline high-performing personality of the FiiO K3.


FiiO K3 Gain tests

While testing the performance of the gain modes of the FiiO K3 we wanted to check if the unit was able to conserve the same flat and non-adulterated sound.

The test results and measurements showed that the FiiO K3 can add the additional gain by going from Low Gain mode to High Gain mode and keep the flat response with no additional sound variation.

At the same time, it is able to provide the exact same +6dB with Bass Boost turned on while being used either in Low or High gain.

The FiiO K3 technical specifications list a frequency response of 20Hz-80,000Hz, with a THD+N lower or equal to 0.004%, SNR of 113dB, line out reaching 1.9Vrms and output impedance of <1.04Ω.

FiiO informs that the FiiO K3 can safely drive headphones having an impedance 16Ω to 150Ω. Moreover, the tiny amp can deliver an output power up to 320mW(16Ω); 200mW(32Ω) (on TRRS 2.5mm balanced).

Testing the FiiO K3 with harder to drive headphones such as the AKG K701 and AKG K612 Pro, the K3 managed to driver them without major issues once set to high gain.


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FiiO K3
FiiO K3


FiiO K3 vs FiiO E10K

The FiiO K3 is released as an advanced replacement of the FiiO E10K and we understand that many of the users might be wondering what are the main differences that set the FiiO K3 apart and above the FiiO E10K.

Taking a look at both the FiiO K3 vs FiiO E10K, the FiiO K3 shows major technological upgrades and specifications, like:

FiiO K3 vs FiiO E10K Bass Boost

The FiiO K3 vs FiiO E10K Bass Boost shows an increment of +1dB on the FiiO K3 over the FiiO E10K. The FiiO K3 now offers a +6dB Bass Boost instead of the +5dB of the FiiO E10K.

FiiO K3 vs FiiO E10K Output Power

The FiiO K3 vs FiiO E10K Output Power has been doubled for the FiiO K3, reaching up to 320mW (16Ω) thanks to it’s balanced output while the FiiO E10K reached a maximum output power of 160 mW (16Ω)

FiiO K3 vs FiiO E10K DAC

The FiiO K3 vs FiiO E10K DAC capabilities now reach up to 384kHz/32bit on the FiiO K3 vs the 96kHz/24bit of the E10K. Moreover, the FiiO K3 now is capable of handling DSD256.

FiiO K3 vs FiiO E10K output connectors

The FiiO K3 vs FiiO E10K output connectors is one of the most visible changes. The FiiO K3 offers 5 connections: 3.5mm, 2.5mm balanced, optical out, coax out and line out while the FiiO 10K was limited to 3 connections lacking a 2.5mm balanced headphone output connector and an optical out. Also, the coaxial out of the FiiO K3 has a higher 192kHz capability and supports DSD64 DOP (96kHz and no DSD support on the previous E10K model)

FiiO K3 vs FiiO E10K Line Out

The line out of the FiiO K3 tops at 1.9Vrms vs the FiiO E10K limited at 1.3Vrms.

FiiO K3 vs FiiO E10K Frequency Response

The FiiO K3 vs FiiO E10K frequency response differs on the upper end, with the K3 extending up to 80kHz while the E10K reached 20kHz.

FiiO K3 vs FiiO E10K Volume Control

The FiiO K3 vs FiiO E10K volume control shows a huge improvement. The FiiO E10K makes use of an analogue knob control while the FiiO K3 has been upgraded to a better performing digital volume knob with no channel imbalance and more accurate sensitivity.

FiiO K3 vs FiiO E10K USB and LED

The FiiO K3 vs FiiO E10K have different USB connections, the K3 introduces a USB Type-C connection and RGB LED light with sample rate indicators while the E10K had a micro USB connection and a blue-only LED for power confirmation.

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FiiO K3
FiiO K3


FiiO Driver

The FiiO K3 offers 2 USB modes: UAC 1.0 and UAC 2.0. These modes have a main difference, the 1.0 mode is a driverless mode with a plug and play functionality while the 2.0 mode requires the installation of the FiiO USB Driver and Control Panel.

For on-the-go use and situations with compatibility issues, the USB Audio Class 1.0 driverless option grants easy connections and high quality audio up to 96kHz, 24-bit PCM audio.

While the Audio Class 2.0 with the installation of the FiiO USB Driver offers extreme audio quality up to 384kHz, 32-bit and DSD256 decoding.

The FiiO USB Driver for the FiiO K3 can be downloaded on this link from FiiO’s repositories.

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Scores Scores

FiiO K3 Scores

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Frequency Response (raw)

FiiO K3 Frequency Response Curve – Low Gain and Bass Boost On and Off

FiiO K3 with 1MORE headphone.
Blue= Bass Boost On; Green= Bass Boost Off; Red= Reference without FiiO K3.

FiiO K3 frequency response curve - Low Gain - Bass Boost On & Off
FiiO K3 frequency response curve – Low Gain – Bass Boost On & Off

FiiO K3 Frequency Response Curve – High Gain and Bass Boost On and Off

FiiO K3 with 1MORE headphone.
Green= Bass Boost On; Yellow= Bass Boost Off; Red= Reference without FiiO K3.

FiiO K3 frequency response curve - High Gain - Bass Boost On & Off
FiiO K3 frequency response curve – High Gain – Bass Boost On & Off

FiiO K3 Frequency Response Curves

FiiO K3 frequency response
FiiO K3 frequency response
FiiO K3 frequency response - High Gain vs Low Gain
FiiO K3 frequency response – High Gain vs Low Gain

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FiiO K3 Technical Specifications

Max output320mW
DSDYes, native DSD256
SNR>113 dB (A-weighted)
Bass BoostYes, 0/+6dB
Drive ability16-150Ω
Frequency Response20Hz-80kHz
USB typeUSB Type-C
WeightApprox. 82g
Balanced 2.5mm outputYes

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FiiO K3 Full technical specifications

reported by FiiO

Model No. K3
USB Type-C
USB Audio Class UAC1.0 + UAC2.0
Volume Knob ADC
Gain L/H
Bass Boost 0/+6dB
Line Out 3.5mm
Headphone Out 1 3.5mm single-ended output
Headphone Out 2 2.5mm TRRS balanced output
Coaxial Out RCA for 192kHz, support DSD64 DOP
Optical Out Up to 96kHz
Audio DAC AKM AK4452
Driver OP AMP OPA926×2
Output Power 1
(3.5mm headphone output) 220mW(16Ω)
Output Power 2
(2.5mm TRRS balanced headphone output) 320mW(16Ω)
Line Level 1.9Vrms
DAC 384kHz/32bit
SNR ≥113dB
THD+N ≤0.004%
Frequency Response 20Hz-80kHz
RGB indicator Sample rate ≤ 48kHz – Blue
Sample rate >48kHz – Yellow
DSD format – Green
Dimensions 70×58×22mm
Weight 82g

Coaxial Out RCA for 192kHz, support DSD64 DOP
Optical Out Up to 96kHz
Drive Ability 16-150 Ω
Power Input Recommend DC5V 500mA
Output Impedance <1.04 Ω
Crosstalk ≥70 dB (1 kHz)
MAX Output Voltage 7.39 Vp-p
MAX Output Current 81.6 mA


FiiO K3 Photos

We highly discourage anyone from trying to apply our testings to your own earphones, the risk of damaging or permanently breaking your iems is absolutely probable to happen. With our standardized equalization and amplification tests we push the limits of the earphones to the extreme. If anyway you decide to do so, we cannot be held responsible of the damage done to your equipment. Do it at your own risk.

meze 99classics, meze 99neo, 1more quad-driver, FiiO K3

FiiO K3