Aimed at audiophiles and music enthusiasts, the black FiiO K9 Pro ESS is a compact, high-fidelity 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 32-bit / 384 kHz PCM sampling rate and native DSD256.
The device is equipped with 4.4mm and stereo RCA analog line inputs, optical and coaxial digital inputs, USB-B and USB-C ports, and XLR and 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.
At a Glance
- Drive power hungry headphones (desktop USB audio + headphones)
- Connect to home audio setups (desktop USB audio + active speakers)
- Side-mounted USB-C port for easy connection to mobile devices
- RCA + XLR balanced line out (for active speakers, monitors, external amplifiers)
- Connect to mobile devices (players, computers)
- Built-in Bluetooth Low Energy (BLE) technology allows you to use the FiiO Control app to control functions like filter selection, channel balance, and more even when not in Bluetooth mode.
Next Gen DAC for High-Resolution Sound
Inside the K9 Pro ESS are two ES9038PRO DAC chips, specifically designed for maximum performance in desktop-grade equipment. One ES9038PRO chip, with all its 8 parallel outputs, is used for each channel to achieve richly detailed sound with minimal distortion.
Pure Clean Sound
The THX AAA 788+ chips used in the K9 Pro ESS provide exemplary details and dynamics no matter if you are using low or high-impedance headphones. The K9 Pro ESS can produce 1100mW under a 300-ohm load and 2100mW under a 32-ohm load undistorted, and 50% higher than the original THX AAA 788 amplifier chips.
Precision Design
- Fully differential signals go through the DAC, volume adjustment, and amp for a truly balanced design. Such a design ensures minimal interference between different components in order to fully maintain all details and large dynamic swings in music for unmatched sound quality.
- The PCB of the K9 Pro ESS uses a partitioned layout, where the power supply and signals are not only separated, but the analog signal loop is also put in an independent section guaranteeing the integrity of the audio signal being processed.
- Every audio signal goes through a mammoth 6-stage circuit to reproduce music as faithfully and as detailed as possible.
Robust Power Supply
- Electricity is the mother of sound, so special attention was paid to optimizing the K9 Pro ESS's power supply to ensure excellent sound. The K9 Pro ESS's linear power supply—with its low-frequency transformer and four massive 4700uF capacitors—makes sure that the rest of the system gets abundant clean power.
- The digital portions of the K9 Pro ESS physically receive power separately from the analog portions for effective shielding against audio interference between the two circuits. This ensures pure and faithful reproduction of your music.
- Besides the special high-performance linear power supply, the power stabilization and filtering within the audio circuit is also a big contributor to the K9 Pro ESS's excellent sound. Specifically, in each stage of the audio circuit, ultra-low-noise LDOs are employed for voltage regulation.
Precision Clock Management
A dual-mode clock management design is utilized for the K9 Pro ESS. Under USB and Bluetooth decoding, dual asynchronous femtosecond clocks are used, while under optical and coaxial decoding, automatic PLL clocks are employed. A more precise clock management system makes it easier to handle any kind of source and maintain the maximum quality possible.
MQA Renderer, Lossless Sound Reproduction
The K9 Pro ESS supports the unfolding of MQA tracks, allowing you to listen to high-resolution audio files that are not only reasonably sized, but also retain master-level sound quality that bring you directly into the recording studio.
Hi-Res Bluetooth
The K9 Pro ESS employs the Qualcomm QCC5124 chip to handle Bluetooth duties, with support for formats such as LDAC, aptX HD, and aptX Adaptive. This chip ensures that Bluetooth connections are both reliable and quick, satisfying both the low latency needs for games/videos and the high bitrate necessary for high-resolution audio.
Next-Level Volume Control
Adjusting the volume may look like a simple concept, but a good execution of it is crucial to an excellent audio experience. The ADC curve reconstruction method of volume adjustment used in the K9 Pro ESS effectively minimizes any left-right channel volume imbalance and noise. It also results in a smooth change of volume across all levels. This attention paid to the simple process of volume adjustment is just another layer to making sure you truly savor your music with the K9 Pro ESS.
Lighting Up the Mood
The RGB indicator lights surrounding the volume knob light up differently depending on the currently playing sample rate.
Three Gain Levels
Choose between high, medium, and low with a physical switch to fit your needs when listening to your particular pair of headphones. Thanks to the pure hardware gain circuit, even when listening at low gain with high-sensitivity headphones both dynamic range and musical fidelity remain uncompromised.
Custom Stand
The included custom stand not only reduces the amount of space the K9 Pro ESS takes on your desktop, it also allows for more efficient dissipation of heat through convection, making the stand a true example of both form and function.