The most basic function of an audio interface is a piece of equipment that allows you to get audio into your computer from a microphone or instrument and back out of your computer to speakers or headphones.

Why do you need to buy an audio interface?

You might be thinking:

“Why do I need to buy an audio interface?
My computer already has a microphone and I can connect my headphones to it.”

This is correct, computers already have built-in audio interfaces, often known as sound cards, but they're not designed for the highest quality recording/playback. Also, most computers are too small to be able to host the connections you need to connect good quality microphones or instruments. 

So, the main reasons you need an audio interface are to do with quality and connectivity. Without an audio interface, you are limited in the quality of audio you can record and playback, the types of microphones and instruments, and headphones and speakers you can use. 

Key functions of an audio interface

Conversion - ADC and DAC

The reason, audio interfaces are sometimes referred to as “converters”.

Analogue to Digital conversion (ADC)

When you play an instrument or sing into a microphone, the sound is captured as an analogue signal. The audio interface converts this signal into digital data that your computer can process, ensuring that every detail of your performance is preserved with clarity.

Digital to Analogue Conversion (DAC)

After your computer processes and manipulates your audio (e.g., applying effects or mixing), the audio interface converts the digital data back into an analogue signal. This is what you hear through your speakers or headphones.

Low-latency monitoring

A quality audio interface provides low-latency monitoring, meaning you can hear yourself in real time without noticeable delay. This is essential for recording vocals or instruments where timing is critical.

Gain and phantom power for microphones

Many professional microphones need “gain”*, provided by a preamp, to boost the level so it's loud enough to record. interfaces have preamps to provide this gain.

Some mics need an external power source known as phantom power. Most audio interfaces provide this, allowing you to use high-quality microphones in your recordings.

*if you're a guitar player, gain often has different connotations. In this case, microphone preamps boost signals cleanly, most of the time aiming for as little distortion as possible.

Multiple inputs and outputs

Depending on your setup, you might need several inputs and outputs. An audio interface can offer multiple channels, allowing you to connect various instruments and microphones simultaneously and route audio to different destinations, such as monitors, headphones, or other equipment.

Choosing the right audio interface

When you're looking for an audio interface, you need to consider a few things:

• How many inputs and outputs do you need? If you're recording a full band simultaneously, you'll need enough inputs to mic up, or connect each instrument.
• Do you need MIDI connections? If you're using MIDI controllers or instruments, make sure your interface supports MIDI.
• Portability: If you plan to record on the go, consider a more compact, bus-powered interface.
• Connectivity: Ensure the interface is compatible with your computer, many interfaces use USB, but you can also find Thunderbolt and Ethernet interfaces for bigger recording setups.
• Other features: Some interfaces have features that can improve your workflow (like Auto Gain, or Clip Safe) and some have extra features to give you more creative options when recording, like preamp settings.