The Fiio Q Series refers to Fiio's line of portable digital-to-analog converters (DACs) and amplifiers, including models like the Fiio Q1, Q3, and Q5. These devices are often used to improve audio quality by providing high-fidelity sound through USB or other connections when paired with a computer, smartphone, or other devices. To use a Fiio Q Series DAC/AMP with a Windows computer, you typically need to install the driver to ensure it works correctly.