FiiO K15 Desktop DAC and Headphone Amplifier

The FiiO K15 is an all-in-one desktop DAC, streamer and headphone amplifier that combines retro elegance with modern technology. It is among the first products to use two of AKM’s new high-end AK4497S DACs, with a fully balanced audio circuit and a discrete class AB amplifier delivering up to 3,000mW per channel, and it streams over Roon Ready, AirPlay and QPlay, plays music from USB drives and NAS, and takes almost any digital or analogue source. A 3.93-inch touch screen, five knobs, a remote and the FiiO Control app put it all at your fingertips. In Japan, it won VGP 2025 Summer awards, including a Gold Award for pure audio.

Dual AKM AK4497S DACs with VELVET SOUND

The two AK4497S chips use AKM’s upgraded VELVET SOUND technology, the philosophy behind AKM’s new-generation audio products, which aims for true-to-life sound reproduction. They achieve low distortion, a wide dynamic range and extended signal bandwidth at low power consumption, keeping rich detail in both the low and high frequencies for a natural, immersive sound.

Fully balanced from DAC to headphone amp

From DAC decoding through low-pass filtering and gain control to headphone amplification, the K15’s audio circuit is fully differential. That ensures a wide dynamic range while effectively reducing crosstalk and noise, for better-quality audio.

A discrete amplifier with 3,000mW per channel

The headphone amplifier is a carefully designed discrete circuit with an op-amp plus transistor current-boosting design: a complementary pair of the classic ON Semiconductor MJE243G/253G transistors, working in class AB, delivers high current with low output impedance. It reaches up to 3,000mW + 3,000mW into 32Ω from the balanced outputs and 700mW per channel into 300Ω, so the K15 drives both full-size headphones and in-ear monitors effortlessly, with a smooth, natural and melodious sound. Five gain levels (low, medium, high, super high and ultra high) match it to each pair.

Eight working modes

• USB DAC: a 16-core XMOS XU316 plays PCM up to 768kHz/32-bit, native DSD512 and fully decoded MQA from a computer or phone, through the front or rear USB-C port (the front takes priority). It draws no power from your phone. Macs need no driver; Windows uses FiiO’s free USB DAC driver, and a driver-free mode (FiiO calls it Switch mode) is available too.
• Coaxial and optical: up to 192kHz/24-bit and DSD64 over coaxial, and 96kHz/24-bit over optical.
• Line in and balanced in: RCA and 4.4mm analogue inputs, amplified by the K15.
• Bluetooth: a Qualcomm QCC5125 Bluetooth 5.1 receiver with LDAC, aptX Adaptive, aptX HD, aptX LL, aptX, AAC and SBC, for music (not calls).
• Streaming: Roon Ready, AirPlay and QPlay from devices on the same network, up to 384kHz/32-bit and DSD256.
• Local playback: play files up to 384kHz/32-bit and DSD256 from a USB flash drive in the rear USB-A port, or from a NAS on your home network.

Five outputs for headphones and speakers

On the front are 6.35mm single-ended, 4.4mm balanced and 4-pin XLR balanced headphone outputs; on the back, an RCA line output (2.4Vrms) and an XLR balanced line output (4.8Vrms). The output knob chooses PO for headphones, PRE for a volume-controlled feed to active speakers or a power amplifier, LO for a fixed full-level feed to an amplifier with its own volume control, or PO+PRE for headphones and speakers together. The three headphone sockets work at the same time, but FiiO advises against using two pairs for long, especially if their impedances are very different.

Physically separated boards

The power supply, digital and analogue sections each sit on their own physical board, preventing crosstalk and protecting the precision and integrity of the audio signal. Silver-plated oxygen-free copper wires connect the boards for high-fidelity signal transfer with minimal loss.

AC or DC power

The K15 has a built-in next-generation 30W (12V, 2.5A) industrial and instrumentation-grade power supply: low noise, highly efficient and long-lasting, rated for 500,000 hours and for operating temperatures from −40°C to 85°C. It also accepts an external 12V DC supply (at least 2.5A), so you can upgrade to a higher-performance linear power supply for even better sound; a switch on the back selects AC or DC.

The digital and analogue sections have separate supplies, for better isolation and resistance to interference. The analogue section has a precisely segmented multi-stage supply, with stages for the DAC, the low-pass filter and the transistors, using up to 14 low-dropout linear regulators for continuous, stable and pure power.

Two femtosecond clocks

Two industry-leading ACCUSILICON AS318-L ultra-low phase noise femtosecond oscillators (45.1584MHz and 49.1520MHz, one for each family of sample rates) effectively reduce phase-noise interference, so audio at every sample rate is reproduced precisely, for purer and more stable sound.

High-end parts

Two Nichicon 3,300µF audio capacitors, four ELNA SILMIC II and eight ELNA RA3 audio capacitors give a higher quality sound with a better soundstage. Eight film capacitors and 32 wafer resistors offer low temperature drift and low noise, for stable sound in hot and cold rooms alike, and Beryl capacitors with ultra-low ESR and strong resistance to interference keep the power supply stable and pure.

Two processors for a smooth experience

A high-performance X2000 multi-core processor, with dual XBurst 2 cores and an XBurst 0 micro-core, delivers excellent computing performance at very low power consumption for precise audio processing and stable, smooth playback. An ESP32-S3 MCU, with a dual-core Xtensa LX7 processor running at up to 240MHz, handles precise system control for a fast, responsive experience.

10-band PEQ

Every digital input (USB, coaxial, optical, Bluetooth, streaming and local playback) supports a 10-band high-precision PEQ, using FiiO’s own algorithm and interface. Fine-tune the sound to your taste, or simulate and modify your headphones’ frequency response. Set it in the FiiO Control app with your phone on the same network, or in FiiO’s web PEQ tool on a computer connected to the rear RS232 port. The PEQ does not work on the line and balanced inputs.

Square and round, with four ways to control it

FiiO’s signature design blends square and round, retro elegance and cutting-edge technology, and its grille structure improves heat dissipation. Control it by touch on the custom 3.93-inch bezel-less screen (240 × 1,020), with the five knobs, with the included infrared remote or from the FiiO Control app. The knobs switch it on and off, choose the output (PO+PRE, PO, PRE or LO), set the gain (L, M, H, SH or UH), and adjust the volume and menus; the volume and menu knobs also press (once set in the menu, a press of the volume knob mutes or turns the screen off), and their light rings have customisable colour and brightness, always on or pulsing. The screen shows the working and output mode, track format and sample rate, EQ, volume, gain, network status and Bluetooth codec, plus VU meters in streaming and local playback (except with DSD). Standby from the remote wakes instantly.

Protected against the unexpected

Besides rigorous testing in FiiO’s labs, the K15 has protection systems that detect abnormal conditions and act automatically to protect you and the device: DC overvoltage protection, DC output protection, power input overcurrent protection, amplifier temperature detection, overvoltage protection (OVP) and output overload detection.

Wired or wireless

A gigabit Ethernet port gives fast, stable wired streaming, and the AP6256 Wi-Fi module supports 2.4GHz and 5GHz networks as another stable way to stream lossless audio.

K15 or K17?

The two look nearly identical. FiiO’s K17 adds a dedicated DSP chip with a 31-band PEQ that also works on the analogue inputs, AKM’s flagship AK4191 + 2 × AK4499EX DACs, a 35W linear power supply, coaxial and optical outputs, a trigger input, a ground-lift switch and 4,000mW of balanced power. The K15 has a 10-band PEQ for digital inputs, dual AK4497S DACs, a switching supply with an external DC option, and 3,000mW.

Good to know

• The power supply accepts any mains voltage from 100V to 240V, so there is no voltage switch to set.
• The M4 grounding terminal on the back helps when you pair the K15 with equipment that cannot connect to mains earth, and can reduce ground-loop interference.
• The rear USB-A port supplies 500mA, enough for a flash drive; a portable hard drive needs its own power.
• Which headphone output is best? FiiO says the 4.4mm and XLR4 balanced outputs are much the same and have more power than the 6.35mm socket, and recommends trying each with your headphones.
• There are no digital (coaxial or optical) outputs, and Bluetooth is for music only.
• In the box: K15, AC power cable, remote control, XLR4 plug cover, spare fuse, two USB cables, headphone plug adapter, quick start guide and warranty card.
• Want more? See the FiiO K17 and the studio-grade flagship FiiO K19.