FiiO K17 R2R Desktop DAC and Headphone Amplifier

The FiiO K17 R2R is a desktop DAC, network streamer and headphone amplifier that pairs FiiO’s own R2R PRO resistor-ladder DAC with the K17’s 4,000mW discrete amplifier, and dresses it in metal and real wood. In FiiO’s words, the warm touch of natural wood speaks to the eyes and hands, while the rich, full-bodied R2R sound brings the warmth of analogue back to your ears. It streams with Roon Ready, AirPlay and Qplay, plays from your NAS, decodes from a computer, phone or digital source, and offers a 31-band lossless PEQ with Auto EQ in every mode.

FiiO’s 24+5-bit segmented R2R PRO DAC

Instead of a DAC chip, the K17 R2R converts with FiiO’s own segmented resistor array. In this segmented design, the upper five bits are decoded by 31 thermometer-coded resistors, which avoids the error build-up of a traditional R2R ladder and reduces distortion. FiiO’s self-developed, new-generation FPGA architecture feeds PCM and DSD to the array, with a choice of OS (oversampling) or NOS (non-oversampling) modes. The result is the sound people love R2R for: clear yet smooth, natural, warm and endlessly listenable.

Three low phase noise femtosecond oscillators, two ACCUSILICON AS318-L (45.1584MHz and 49.1520MHz) and a FiiO-customised 12MHz part, greatly reduce the effect of phase noise, so every sample rate is restored precisely for a purer, more consistent sound.

Fully balanced, with a discrete 4,000mW amplifier

The whole circuit is fully differential, from the DAC through I/V conversion and low-pass filtering to the headphone amplifier, for high dynamic range and much lower crosstalk. FiiO’s diagram shows OPA1612 op-amps for I/V conversion, OPA1642 op-amps after them, and an NJW1195A volume control. The headphone amplifier is a carefully crafted, fully discrete op-amp plus transistor current-amplification design, built around the classic ON Semiconductor MJE243/253 pair: it delivers high current with low output impedance, for up to 4,000mW + 4,000mW from the balanced outputs, nearly double the K9 Pro ESS, easily driving all kinds of headphones and IEMs with a smooth, pleasant and natural sound.

A 64-bit DSP for a 31-band lossless PEQ and Auto EQ

An M21586Q DSP (double-precision 64-bit floating point at 360MHz), an ES9821Q ADC and a custom femtosecond oscillator let you use the 31-band high-precision lossless PEQ in every mode, analogue inputs included, and provide robust output protection. FiiO’s DEL (Dual Engine Limiter) adds dynamic range compression and expansion, a limiter and a compressor; PCM from 44.1kHz to 96kHz is processed without sample-rate conversion; and each band offers gain from +12 to −24dB and a Q from 0.4 to 128. Export, import and share settings, or let Auto EQ match your headphones to a target curve in one tap, alongside Pop, Jazz and Classical presets and band-by-band tuning.

Separate boards and a 35W linear supply

The power supply, digital and analogue sections sit on physically separate circuit boards to avoid interference. A custom low-noise transformer feeds a 35W linear supply with five large 4,700µF capacitors for ample reserves; the digital and analogue circuits have separate supplies; and the analogue circuit has a multi-stage supply, with dedicated regulation for the DAC and filter stages using LT3045, TPS7A4701 and TPS7A3301 low-noise, high-PSRR regulators.

High-end parts

Rubycon solid capacitors with ultra-low ESR keep the power stable and pure, joined by four Nichicon audio capacitors, four ELNA SILMIC II, six ELNA RA3 and four WIMA audio capacitors for a high-quality sound and a grand soundstage. Four sets of silver-plated oxygen-free copper cables carry the audio between boards with minimal loss, and tulip-shaped, gold-plated NEUTRIK connectors resist oxidation and wear.

Streaming, NAS and eight working modes

With Roon Ready, AirPlay and Qplay certification, the K17 R2R works with the platforms and devices you already use, and NAS playback (NFS and SMB) brings your home library in with one tap in the FiiO Control app. It connects by gigabit Ethernet or dual-band 2.4GHz/5GHz Wi-Fi (AP6256). FiiO’s usage scenarios show the range: a computer over USB with headphones and active speakers connected at once; music from a NAS through the app; Roon Ready with the Roon Remote app; an amplifier and passive speakers playing AirPlay from an iPad; a digital audio player on the front USB port; a USB flash drive or portable hard drive played locally; or an analogue source processed by the PEQ and sent to headphones or the line output.

Two processors

An X2000 multi-core processor (an XBurst 2 main core with two logical CPUs plus a small XBurst core) gives precise audio processing and stable, smooth playback at low power, and a low-power ESP32-S3 with a dual-core Xtensa LX7 running at up to 240MHz keeps the interface fast and smooth.

Square and circle, with real wood

The side panels reimagine FiiO’s square-and-round design in natural wood from North America: imported ash on the silver model for a crisp, quietly elegant look, and imported black walnut on the black model for a deeper, more reserved feel. Every grain is different, so no two units look quite the same. A grille helps it dissipate heat.

Many ways to control it

The custom 3.93-inch touch screen gives quick access to settings and functions. Five knobs adjust the volume, gain, output and other settings (standby takes one press), the included aluminium infrared remote switches modes, EQ and volume from your chair, and the FiiO Control app covers local playback, NAS and more. Protection for the headphone amplifier and transformer temperature, output overload, output DC and power-input overcurrent steps in automatically if anything goes wrong.

Good to know

• FiiO has not yet published separate measurements for the K17 R2R; ask us if you need a specific figure.
• For AKM conversion in the same chassis, see the FiiO K17.
• In the box: K17 R2R, AC power cord, aluminium remote control, XLR4 plug cover, spare fuse, two USB cables, headphone plug adapter, quick start guide and warranty card.