What is aux

Overview

Aux is an abbreviation for 'auxiliary,' meaning secondary, backup, or supplementary. In modern technology, aux most commonly refers to auxiliary input or output connections on audio equipment, though the term appears across many industries to describe secondary systems or components. The widespread adoption of digital devices and headphones has made aux connectors ubiquitous in consumer electronics.

Aux in Audio Systems

In audio contexts, auxiliary inputs and outputs serve as secondary connection points on receivers, amplifiers, mixing boards, and other audio equipment. An aux input allows users to connect external audio sources—such as a smartphone, tablet, MP3 player, or synthesizer—to the primary audio system. The auxiliary input signal is then routed through the system's amplification and speaker setup. An aux output allows routing audio signals from a primary source to secondary destinations like external amplifiers, recording devices, or monitoring systems. This flexibility is essential in both professional studios and home audio setups.

Common Aux Connectors and Standards

Multiple physical connector types serve auxiliary functions. The 3.5mm headphone jack (mini jack) is perhaps the most recognizable, found on countless consumer audio devices including smartphones, laptops, and portable speakers. Professional audio systems commonly use XLR connectors or 1/4-inch phone jacks, which offer more robust connections suitable for studio and live performance environments. RCA connectors, featuring red and white plugs, are traditional aux connectors found on receivers and consumer audio components. USB connections increasingly serve auxiliary functions for digital audio transmission and device charging.

Aux in Vehicles

In automotive contexts, an auxiliary input allows drivers to connect external audio devices directly to a vehicle's audio system. Before wireless Bluetooth became standard, aux inputs were the primary method of playing personal music through car speakers. Many vehicles still include aux inputs despite Bluetooth availability, providing a reliable wired connection option that doesn't depend on wireless connectivity or battery life of the connected device.

Broader Applications

Beyond audio, 'aux' terminology appears throughout technology and transportation. Aircraft have auxiliary systems for backup hydraulics, power, and navigation. Vehicles have auxiliary power outlets for charging devices. Computer systems have auxiliary storage and processors. In all these contexts, aux refers to secondary, supporting systems that enhance primary function while maintaining independence.