How to Set Up a 4-Input Audio Interface | Hook Up Four Mics Fast

A 4-input audio interface lets you record four analog sources at once, and the first-time setup comes down to one thing: plugging each source into the right jack. The Focusrite Scarlett 4i4 4th Generation, a current US-market example, shows exactly how the layout works. It pairs 2 front-panel combo inputs with 2 rear-panel line inputs, so the front jacks handle microphones and the rear jacks handle line-level gear like synths and drum machines.

What Each Input On The Interface Is For

The Scarlett 4i4 4th Gen uses two different connector types, and mixing them up is the most common first-time mistake. The two front-panel Neutrik XLR combo jacks accept mic, line, and instrument signals, with automatic mic/line switching on the combo inputs. The two rear-panel 6.35 mm jacks are line inputs only — plugging a microphone into the rear is the setup error that produces silence.

The four-input map breaks down like this:

• Combo input 1 (front): mic, line, or instrument — best for a vocal mic or guitar.
• Combo input 2 (front): mic, line, or instrument — best for a second mic or bass.
• Line input 3 (rear): line-level source, such as a keyboard, synth, or drum machine.
• Line input 4 (rear): a second line-level source.

That topology is common across 4-input interfaces in this class, so the habit of checking front versus rear jacks carries over to other brands.

The Step-By-Step Hookup

Connect everything in a sensible order, and the interface will appear in your software without a struggle. Focusrite’s own user guide documents this workflow, and the sequence below matches it.

1. Connect the USB-C cable from the interface to your computer.
2. Install the manufacturer’s driver or control software if your system requires it. The Scarlett 4i4 4th Gen is a USB-C desktop interface for Mac and PC, and the computer must have compatible software support for the interface’s driver and control app.
3. Plug your sources into the correct inputs — microphones into the front combo jacks, line-level gear into the rear.
4. Select the interface as the system and DAW input/output device in your recording software’s audio settings.
5. Set gain on each channel so the loudest signal hits the meter without clipping.
6. Turn on phantom power only if needed — the front combo inputs support +48 V for condenser mics. Leave it off for dynamic mics, ribbon mics, and any gear not designed to accept phantom power.
7. Route your monitoring in the control app, or use the hardware controls for direct monitoring and headphone levels.

When it works, the interface shows up as an active audio device and the input meters move when you play or speak. The Scarlett 4i4 4th Gen supports 6 × 6 simultaneous I/O including loopback inputs, one headphone output, and MIDI, which covers multi-mic podcasting, small band recording, and synth-heavy setups.

What The Specs Actually Mean For Recording

The Scarlett 4i4 4th Gen records at 24-bit depth with supported sample rates of 44.1, 48, 88.2, 96, 176.4, and 192 kHz. Most sessions should run at 48 kHz — it sounds identical to higher rates for the vast majority of music and podcast work, and it keeps file sizes and CPU load low. Step up to 96 kHz only when a project genuinely needs it, like sound design or certain film work.

The interface has 4 line outputs plus a headphone output. Connect your studio monitors to the four line output jacks, or the first pair for a simple stereo setup, then use the headphone output for tracking. Focusrite lists the current product as the Scarlett 4i4 4th Generation, and the official specifications page documents the sample rates, phantom power, and input topology above.

Which Interface Should You Actually Buy?

Four inputs only helps if the holes match your gear, so check the connector types before you buy. The Scarlett 4i4 4th Gen fits musicians with a couple of mics plus line-level synths or drum machines; it’s less useful if you need four mic preamps, since it only has two.

Before you commit, there’s a roundup of the best 4-input audio interfaces that compares models side by side — worth a read if you’re still weighing options. Either way, check that your computer has a compatible USB port and that the interface offers drivers for your OS, since that determines whether the hardware will work at all.