How Does an Audio Interface Work?
Updated Nov 13, 2026 · By 
Jonah Mercer · Editorial policy
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An audio interface sits between a microphone or guitar and a computer. Its preamp lifts the mic signal, its converters turn that signal into digital audio the computer can record, and it turns digital audio back into sound for speakers or headphones. A USB cable links the interface to the computer on the models here.
The input takes the mic or guitar signal
A microphone or guitar plugs into an input on the interface. The Focusrite Scarlett Solo 3rd Gen has 1 XLR mic preamp and 1 Hi-Z instrument input, and the MOTU M2 has 2 combo XLR/TRS inputs for mic, line or guitar. The M-Audio M-Track Duo has two combo XLR, line and instrument inputs. A mic preamp lifts the small signal from the microphone to a level the converters can use.
The converters turn sound into digital audio
Converters measure the incoming signal many times per second and store each measurement as a number. The sample rate sets how many measurements happen each second, and the bit depth sets how much detail each measurement holds. The Scarlett Solo 3rd Gen, the MOTU M2 and the Scarlett Solo 4th Gen record at up to 24-bit/192kHz, while the M-Audio M-Track Duo records at up to 48kHz. Higher figures give the recording more detail to work with when you edit.
Phantom power runs condenser microphones
Some microphones need power from the interface to work, and that power is 48V phantom power sent up the XLR cable. The M-Audio M-Track Duo lists 48V phantom power on its combo inputs. Dynamic microphones make their signal without outside power, so they do not need phantom power. Check the microphone specs for 48V before you switch it on.
Outputs and headphones play the sound back
The interface sends the recorded sound back out through its outputs and headphone jack. The Scarlett Solo 3rd Gen has 2 low-noise balanced outputs and a headphone connection for private listening. The MOTU M2 has 2 balanced 1/4-inch line outputs and a headphone output with its own volume. The M-Audio M-Track Duo has a 1/4-inch headphone output and stereo 1/4-inch outputs, with a USB/Direct switch for zero-latency monitoring.
Software and drivers link it to the computer
The interface needs a driver and recording software on the computer before it can record. The Scarlett Solo 3rd Gen and 4th Gen include Pro Tools Intro+, Ableton Live Lite, Cubase LE and Hitmaker Expansion. The M-Audio M-Track Duo includes Ableton Live Lite and MPC Beats. The MOTU M2 runs on MOTU drivers and works with macOS, Windows and iOS.
What you need
Focusrite Scarlett Solo 3rd Gen USB-C Audio
A USB-C interface with 1 XLR mic preamp, 1 Hi-Z instrument input and 24-bit/192kHz recording, with Air mode and a 56dB gain range.
- Inputs: 2
- Mic preamps: 1
- Max sample rate: 192 kHz
- Bit depth: 24-bit
- Software named in listing: Pro Tools Intro
- 3-year warranty stated
MOTU M2 USB-C Audio Interface
A USB-C interface with 2 mic preamps, 2-in/2-out, 24-bit/192kHz recording, hardware monitoring and LCD meters for all inputs and outputs.
- Inputs: 2
- Mic preamps: 2, the most here
- Outputs: 2
- Max sample rate: 192 kHz
- Bit depth: 24-bit
- 2-year warranty stated
M-AUDIO M-Track Duo USB Audio Interface Dual
A USB interface with two combo XLR, line and instrument inputs, 48V phantom power and 48kHz recording, with Ableton Live Lite and MPC Beats.
- Inputs: 2
- Max sample rate: 48 kHz
- 48V phantom power
- Software named in listing: Ableton Live Lite
- 0.7 lb, the lightest here
Focusrite Scarlett Solo 4th Gen USB-C Audio
A USB-C interface with 1 XLR mic preamp, 1 Hi-Z instrument input and 24-bit/192kHz recording, with a 120dB dynamic range and Air modes.
- Inputs: 2
- Mic preamps: 1
- Max sample rate: 192 kHz
- Bit depth: 24-bit
- Software named in listing: Pro Tools Intro
These come from our ranked list Best Audio Interface, which compares them spec by spec.
Frequently asked questions
Do I need an audio interface to record a microphone?
Yes, if the microphone has an XLR output. The interface gives it a mic preamp and 48V phantom power if it is a condenser, and turns its signal into digital audio the computer can record.
What is the difference between 48kHz and 192kHz?
They are sample rates, or how many measurements of the sound the interface takes each second. The M-Audio M-Track Duo records at up to 48kHz, while the Scarlett Solo 3rd Gen, the MOTU M2 and the Scarlett Solo 4th Gen record at up to 192kHz.
Can I plug a guitar straight into an audio interface?
Yes. Use the Hi-Z instrument input, which the Scarlett Solo 3rd Gen and 4th Gen have, or a combo input set to instrument on the MOTU M2 and the M-Audio M-Track Duo. Set the gain so the signal stays clear of clipping.
Ranked audio interfaces lists
More how-to guides
Product details come from each Amazon listing and can change. Check the listing before you buy.