FiiO K15 Firmware Update Fixes USB Audio Issues

FiiO K15 desktop DAC/amp (Image: LOMO胖纸/weibo)

The FiiO K15 received its third firmware update today (14). This latest update consists exclusively of bug fixes, addressing issues such as the absence of audio output in USB mode and synchronization failures when enabling PEQ through the web interface. The changes introduced to the K15 and the firmware update procedures are detailed below.

K15 Receives EQ-Related Fixes and More

The third update for the FiiO K15 was released today (14), introducing firmware versions V159 and V97 for the main controller and MCU, respectively. In this update, the manufacturer addressed equalization-related issues and corrected the shuffle mode icon.

Top of the FiiO K15 desktop DAC/amp (Image: LOMO胖纸/weibo)

The changelog for FiiO K15 firmware versions V159 and V97 is provided below.

• Fixed an issue that caused a loss of audio output when playing 44.1 kHz tracks in USB mode after enabling or disabling EQ and then resuming playback.
• Resolved an issue that prevented the K15 from synchronizing with the web version of FiiO Control when enabling or disabling PEQ.
• Fixed a bug affecting the playlist icon on the K15, which incorrectly displayed the shuffle mode icon after streaming audio via QPlay and connecting to the device through the FIIO Control app.

As shown above, this update introduces only bug fixes. However, nearly a month ago, the K15 received several new features that are worth mentioning here:

• Support for NAS servers in local playback mode.
• QPlay support in streaming mode.
• A new menu option in the system settings for customizing the FN1/FN2/FN3 buttons on the remote control.
• The ability to sort tracks by “Album” within the “Artist” and “Genre” categories during local playback. (Note: Update the music library after updating the firmware.)
• A “Disable LO (Line Out)” option in the system settings.

How to Update the FiiO K15 Main Controller Firmware

There are two ways to update the FiiO K15 main controller firmware: over Wi-Fi or locally using a USB flash drive. Step-by-step instructions for each method are provided below.

Updating over Wi-Fi

Step 01: Connect the K15 to a Wi-Fi network.

Step 02: Select Main controller Local Upgrade under Settings → Others → FW Update → Main controller (SOC) → online upgrade.

Updating Locally Using a USB Flash Drive

Step 01: Download the SoC firmware update package to your computer. The update package is compressed in “.zip” format; do not extract it. Copy the file to a USB flash drive.

Step 02: Insert the USB flash drive into the USB-A port on the rear of the K15.

Rear connections of the FiiO K15 desktop DAC/amp (Image: LOMO胖纸/weibo)

Step 03: Select Main controller Local Upgrade under Settings → Other → FW Update → Main controller (SOC) → Local upgrade, and wait for the update to finish. Once the update is complete, the system will restart automatically.

Step 04: After all updates have been completed, turn the AC power switch on the rear panel off and then back on to restart the entire K15 system.

How to Update the FiiO K15 MCU Firmware

The FiiO K15 MCU firmware can only be updated locally using a USB-C cable. Follow the steps below.

Step 01: Download the MCU update package to your computer. The update package is a file with a “.bin” extension.

Step 02: Connect the cable to the USB-C port labeled “RS232” on the rear of the K15, and connect the other end to your computer.

Step 03: Select MCU Upgrade under Settings → Others → FW Update → MCU upgrade. A USB drive will appear on your computer. Copy the update package to this USB drive. Then eject the USB drive, and the update will begin automatically. Once the update is complete, the system will restart automatically.

About the FiiO K15

Released internationally on August 4, 2025, the FiiO K15 is FiiO’s midrange desktop DAC/amp. It sits above the K11 and K13 but below the K17, the brand’s flagship model.

Buttons and connections on the front of the FiiO K15 desktop DAC/amp (Image: LOMO胖纸/weibo)

The FiiO K15 is the only model that does not have an R2R DAC version. It is available exclusively with the AKM AK4497S delta-sigma DAC.

Interestingly, FiiO selected AKM DACs for both the K15 and K17. For the recently released delta-sigma version of the K13, the manufacturer opted for ESS Labs chips, whereas the K11 uses a Cirrus Logic DAC.

In terms of output power, the K15 can deliver up to 3,000 mW into 32 Ω through its balanced 4.4 mm and XLR outputs. The K17 can deliver up to 4,000 mW into 32 Ω through its balanced 4.4 mm and XLR outputs. The K13, in turn, provides up to 2,400 mW into 32 Ω through its balanced 4.4 mm output.