The device is equipped with 4.4mm and stereo RCA analog line inputs, optical and coaxial digital inputs, USB Type-B and Type-C ports, and XLR & RCA analog line outputs. The headphone output connectors include a 1/4" singled-ended jack, as well as balanced 4.4mm and 4-pin XLR headphone jacks. The K9 Pro ESS acts as a bridge between your computer, phone, speakers, and headphones, allowing them to work together seamlessly. Switchable low-, medium-, and high-gain levels are available, enabling you to use the amplifier with almost any headphones at comfortable volume levels.
Aimed at audiophiles and music enthusiasts, the high-fidelity FiiO K9 Pro ESS is a compact desktop USB DAC and headphone amplifier that faithfully reproduces your music when listening to audio from your computer, smartphone/tablet, or other digital music player. The K9 Pro ESS utilizes dual high-resolution ES9038PRO DACs to deliver richer audio details and a superior performance at up to 384/32-bit kHz PCM sampling rate and native DSD256.