Tutorials Audio

Audio Interfaces Explained

Beginner · ~25 min

Overview

An audio interface is the hardware device that connects professional microphones and instruments to your computer. If you own an XLR microphone (the kind used for podcasting, voice over, and music recording) you need an audio interface to use it. The built-in sound card in your laptop is designed for headphones and a webcam microphone, not professional XLR mics. An interface provides the right connector, the right level of amplification (a preamp), and a much higher-quality analogue-to-digital conversion than any internal sound card. Some links in this guide are Amazon affiliate links. If you purchase through them, we earn a small commission at no extra cost to you.

What You Need

An XLR microphone (dynamic or condenser)
An XLR cable
An audio interface (see step 6 for recommendations)
A USB or USB-C cable to connect the interface to your computer

Steps

What an audio interface does

An audio interface performs two core jobs. First: it contains a microphone preamp that amplifies the tiny signal from an XLR microphone up to a level the rest of the system can work with. Microphone-level signals are extremely quiet, without a preamp, you'd hear almost nothing. Second: it contains an analogue-to-digital converter (ADC) that turns the analogue signal from the mic into digital data your computer can record. The quality of both the preamp and the converter directly affects the noise floor, the dynamic range, and the overall sound quality of your recordings.

Inputs, outputs, and I/O count

Interfaces are commonly described by their I/O count, for example, "2-in/2-out." The inputs are the number of simultaneous signals you can record at once. A 1-in or 2-in interface covers solo podcasters, VO artists, and singer-songwriters. A 4-in or 8-in interface is needed for multi-mic setups, interview podcasts with multiple guests in the same room, or recording a drum kit. Outputs are for monitoring. Most entry-level interfaces have a stereo headphone output and a stereo line output for studio monitors. Check you have enough inputs for your workflow before buying.

Preamp quality and phantom power

The preamp in your interface determines how much gain you can apply before noise becomes audible, measured as the equivalent input noise (EIN). Lower EIN means quieter, cleaner preamp. Budget interfaces have preamps that are perfectly fine for dynamic mics and loud sources. Better preamps matter more when using condenser mics or very quiet dynamic mics (like the Shure SM7B) that need more gain. Phantom power (+48V): condenser microphones require phantom power to operate. This is 48 volts of DC power sent up the XLR cable from the interface to the microphone. Every decent interface has a phantom power button (usually labelled +48V). Dynamic mics don't need it and aren't damaged by it. Always ensure phantom power is off before plugging or unplugging a ribbon microphone.

Sample rate and bit depth

Sample rate is how many times per second the interface measures the analogue signal. 44.1kHz is standard for music (CD quality). 48kHz is standard for video and podcast production. 96kHz and 192kHz are used for high-resolution archival or specialist applications. For podcasting and voice over: 48kHz is the correct choice. Bit depth determines the dynamic range of the recording. The gap between the quietest and loudest recordable sound. 16-bit gives 96dB of dynamic range. 24-bit gives 144dB. Always record at 24-bit. It gives you much more headroom when setting gain levels and more flexibility in post. The file size increase over 16-bit is minimal.

How to connect everything

1. Connect your XLR microphone to the interface's XLR input with an XLR cable. 2. If using a condenser mic, press the +48V phantom power button. 3. Connect the interface to your computer with the supplied USB/USB-C cable. 4. The interface appears as a new audio device in your operating system. Set it as the default input in your OS settings or select it in your DAW's audio preferences. 5. Open your DAW or recording software, create a new audio track, and select the interface's input channel. 6. Set your gain: speak at your loudest normal volume and adjust the interface's gain knob until peaks are hitting around −12dBFS to −6dBFS, never clipping (never hitting 0dBFS). 7. Monitor through the interface's headphone output for zero-latency direct monitoring.

Recommended interfaces by budget

Entry (£80 to £130): Focusrite Scarlett Solo (1-in, 1-out) or Focusrite Scarlett 2i2 (2-in, 2-out). The most popular beginner interfaces in the world. Solid preamps, plug-and-play on Mac and Windows. The 2i2 is the better choice if you ever record two mics simultaneously. Mid-range (£200 to £350): Universal Audio Volt 2, warmer preamps with a built-in LA-2A-style compressor. Or the Audient iD14 mkII for cleaner, more transparent preamps and better converters. Professional (£500+): Universal Audio Apollo Twin, onboard DSP processing lets you run UAD plugins with near-zero latency. Audient Evo 16 for 8+ channels at high quality. For pure voice over and podcast: a Focusrite Scarlett 2i2 is all you will ever need.

Pro Tips

Bus-powered interfaces (powered over USB) are more convenient but can occasionally introduce noise from the USB power supply. If you hear a faint buzz or whine, try a different USB port or a powered USB hub.
Direct monitoring (listening to your mic through the interface's headphone output before the computer) has zero latency. Recording through software monitoring introduces a small delay. Use direct monitoring during recording and software monitoring for playback.
Most modern interfaces are class-compliant. They need no driver installation on Mac and work immediately. Windows may need a driver for ASIO support, which reduces recording latency significantly.
The gain knob on your interface sets the preamp level, not the recording volume. Set it correctly before you record. You can't fix clipping in post.

Knowledge Base

What You'll Learn

Choose and set up an audio interface for podcast recording or music production. Learn input/output routing, gain staging, and how interfaces affect sound quality.

What Is an Audio Interface?

An audio interface converts analog signals (from your microphone) to digital signals your computer can record. It also outputs digital audio back to analog so you can hear it in headphones/speakers.

Key Specs to Understand

I/O Count: Inputs and outputs. 2x2 is minimum (1 mic input, 1 headphone output).
Bit Depth: 24-bit is professional standard. 16-bit is adequate.
Sample Rate: 48 kHz is standard. 44.1 kHz for audio-only work.
Latency: Delay between input and output. Lower is better. <5ms is good for recording.

Budget Options

USB Condenser Mic (no interface needed): Audio-Technica AT2020 USB. $100. Simplest setup.
Basic Interface ($50-150): Behringer U-Phoria, Focusrite Scarlett. 2x2 I/O, good for podcasts.
Professional Interface ($200+): Audient iD4, RME Babyface. Low latency, built-in monitoring.

Gain Staging

Set microphone gain so that loud passages peak at -6 dB (provides headroom). Too quiet, and you'll boost noise in post. Too loud, and you risk clipping. Monitor with headphones while setting gain.

Where This Fits

This guide covers one specific part of audio recording. The wider picture, how microphone distance, room acoustics, polar patterns, and gain staging decide whether a recording is usable before any processing, is in Audio Recording Fundamentals: The Complete Guide, which frames the discipline as a whole and links out to the detailed guides underneath it, including this one. If you are starting from scratch rather than solving a specific problem, read that first and come back here.

FAQ

Q: Do I need an audio interface for podcasting?
A: USB mics bypass the interface. USB interfaces are overkill for single-mic recording. Get USB mic if budget is tight.