An audio interface is a piece of hardware that allows the input and output of audio signals to and from a host computer or recording device. It is a physical device that converts microphone and instrument signals into a format that your computer and software can recognize. Audio interfaces are primarily intended to provide low-latency analog-to-digital and digital format conversion for professional audio applications. They are closely related to computer sound cards, but sound cards are optimized for audio playback, while audio interfaces are designed to provide high-quality audio recording and playback.

Audio interfaces may include microphone preamps, as well as analog line inputs, DI inputs, and ADAT or S/PDIF digital inputs. Outputs are analog line, headphones, and digital. They are typically available as external units, either as desktop devices or in a 19-inch rackmount format. Audio interfaces range from two channels in and out to over 30.

An audio interface is more than just a necessary peripheral. It is the centerpiece of all your studio gear, and everything communicates through your interface to your source, whether it be a computer or a recording device. Audio interfaces have inputs for microphones and line-level signals, and they may provide one stereo pair of line outputs for monitor speakers or many outputs for multiple headphones, pairs of monitors, or for surround-sound mixing, external summing, re-amping, and outboard effects processing.

In summary, an audio interface is a crucial piece of hardware for anyone who wants to record high-quality audio on their computer or recording device. It allows you to convert analog audio signals into digital format and vice versa, and it provides low-latency conversion for professional audio applications. Audio interfaces come in many different configurations and specifications, and they range widely in price points.