Dual AKM DAC Chips with THX AAA 788+ Amplification
The FiiO K7 is a compact desktop DAC and headphone amplifier built around a pair of AKM AK4493S digital-to-analogue converters, one dedicated to each channel for a fully discrete stereo signal path. Digital decoding is handled by an XMOS XUF208 controller with dual independent clocks, one for 44.1kHz multiples and one for 48kHz multiples, which reduces jitter and provides precise timing for all supported formats including PCM up to 32-bit/384kHz and DSD up to DSD256.
Amplification is provided by a dual THX AAA 788+ stage running through a six-stage fully balanced analogue circuit. Each stage (DAC module, low-pass filter, volume control, buffer amplifier, gain stage, and relay) operates in balanced differential form to minimise crosstalk and noise before the signal reaches the headphone output. Output power reaches 2000mW into 32 ohms from the balanced 4.4mm output and 1220mW from the 6.35mm single-ended output, making the K7 capable of driving demanding full-size headphones with authority.
Versatile Connectivity
The rear panel provides USB Type-B, optical, coaxial, and RCA analogue line inputs, covering every common digital and analogue source. A pre-amplifier/line-out RCA output allows the K7 to feed a power amplifier or active speakers, enabling use as the analogue stage in a wider hi-fi system. Input selection and gain level are set via front-panel toggle switches, and 112 precisely tuned volume steps ensure fine control at any listening level.
Clean Power Supply Design
The K7 runs from a 12V external switching supply, with independent low-dropout regulators distributing isolated power rails to the XMOS controller, DAC modules, buffer stages, and THX amplifier modules. This separation prevents switching noise from the digital section reaching the sensitive analogue stages. Multiple protection circuits guard against overheating, overload, and DC offset on the outputs.
Front Panel and Indicators
The front panel features an RGB-illuminated volume knob that changes colour to indicate the active input source, a 4.4mm balanced headphone output, and a 6.35mm single-ended headphone output. An output mode switch selects between headphone amplifier mode and pre-amplifier mode for use with powered speakers or a separate power amplifier. The brushed-aluminium chassis measures 120 x 168 x 55mm and weighs approximately 610g.
