The FiiO K13 ESS is a compact desktop DAC and headphone amplifier for anyone who wants one box to drive serious headphones from a computer, streamer or phone, and to feed a pair of active speakers or a power amplifier at the same time. It is the delta-sigma counterpart to the K13 R2R: the two share the same chassis, controls and connectivity, but this version is built around a pair of ESS flagship ES9039Q2M DAC chips for a cleaner, darker background and a more precise, detailed presentation.
Dual ESS ES9039Q2M DACs
Each ES9039Q2M uses ESS's fourth-generation 32-bit HyperStream architecture, chosen for higher performance and lower power consumption while reducing digital noise inside the DAC itself. The entire audio chain, from the DACs through I/V conversion, low-pass filtering and the preamp buffer to the headphone stage, uses fully differential signal processing for interference rejection, minimal distortion and high dynamic range. The USB input is handled by an XMOS XU316 receiver and supports PCM up to 768kHz/32-bit and native DSD512. Eight digital filter settings and a four-step second harmonic regulation (SHR) control let you fine-tune the character of the decoding.
Fully balanced amplification
The headphone amplifier delivers 2400mW + 2400mW into 32 ohms from the 4.4mm balanced output at high gain, and 1220mW + 1220mW from the 6.35mm single-ended output, with 600mW + 600mW balanced still available into 300 ohm loads. Three gain levels with independent volume curves cover everything from sensitive in-ear monitors to demanding full-size headphones, and the amplifier includes gain control, headphone protection and pop-noise elimination. The K13 also doubles as a preamplifier or line-level DAC via balanced XLR and single-ended RCA line outputs, with the headphone and preamp volume levels memorised independently.
Power supply
Power comes from a built-in 30W (12V, 2.5A) industrial-grade module, with up to 18 low-noise LDO regulators and five DC-DC converters providing separate analogue and digital rails. A rear DC input accepts an external 12V, 2.5A or higher linear power supply with a 5.5 x 2.1mm connector, such as FiiO's DARKSIDE PRO, for those who want to upgrade later. Audiophile-grade components include four ELNA RA3 silk-film capacitors, eight WIMA film capacitors, 24 low-temperature-drift MELF resistors and two Accusilicon AS318-L femtosecond crystal oscillators.
Connectivity
Digital inputs comprise two USB-C ports (one on the rear, one on the side), a coaxial S/PDIF socket that can also act as a coaxial output, an optical input and Bluetooth 5.4 with support for LDAC, AAC and SBC. Outputs are the 4.4mm balanced and 6.35mm headphone sockets on the front, plus XLR balanced and dual RCA line outputs on the rear. An infrared remote control is included.
Control and EQ
Two front knobs handle input and menu navigation on the left and power and volume on the right, with a 1.1-inch LCD showing sampling rate, volume, gain and output mode. A 10-band parametric equaliser works across all operating modes and can be set through the FiiO Control app or a web interface, where AUTO EQ matches a target curve for popular headphones with one tap before you fine-tune it. The RGB rings around the knobs and the top ambient light indicate the current sampling rate and can be customised for brightness, colour and pulsing, and a 1 to 99 minute sleep timer is built in.
Design
The thickened unibody aluminium alloy casing continues the minimalist language of the K11 series, with a circular skylight in the top panel that gives a view of the DAC board beneath. The unit measures approximately 210 x 188 x 42mm including feet and weighs around 960g. Available in Black and Silver; this listing is for the Black finish. Supplied with an infrared remote control, AC power cord, USB data cable, headphone adapter, quick start guide and warranty card.
