Scarlett 18i20 - Audio Interface Quick Guide

When using the iMac, ensure that the default audio input and output are set to the Scarlett 18i20. To check this:

  1. Open System Preferences → Sound.
  2. Confirm that both Input and Output are set to Scarlett 18i20.

This setting also needs to be verified within any audio editing or playback software (e.g., Reaper, FL Studio) to ensure proper recording and playback. If Scarlett 18i20 is not showing up in audio settings or not recognized as the input/output device, follow the trouble shooting guide.

Front Panel of Scarlett 18i20
Front Panel of Scarlett 18i20

The quick guide below covers the basics of Scarlett 18i20 front panel.

Inputs & Gain

  • Inputs 1 & 2 - For plugging in microphones or instruments. The Shure SM58 is connected to Input 1.
  • Gain 1 & 2 - Adjusts the recording level for Inputs 1 & 2.
  • INST - Turns Inputs 1 & 2 into high-impedance instrument inputs (e.g., guitar). Leave off unless plugging in an instrument directly.
  • Inputs 3-8 & Gain 3-8 - Located on the back; use gain knobs here to adjust their levels.

Microphone Power & Sound Shaping

  • 48V (Phantom Power) - Needed for condenser microphones. Two switches: one powers Inputs 1-4, the other powers Inputs 5-8.
  • PAD - Lowers input signal by 10 dB to prevent distortion from loud sources.
  • AIR Mode - Adds brightness and presence to the sound; enabled via Focusrite Control.

Level Monitoring

  • Input Meters - LED bars show input level. Avoid hitting the red light (digital clipping).
  • USB active Icon USB Active LED - Green light means connected to the computer.
  • Locked LED Icon Locked LED - Shows the unit’s clock is synced properly.
  • MIDI LED - Lights when receiving MIDI data.

Monitor & Output Controls

  • MONITOR - Main volume for the studio speakers.
  • DIM - Instantly lowers speaker volume by 18 dB.
  • MUTE - Silences speakers.
  • ALT - Switches output between main speakers and a secondary set (set in Focusrite Control).

Communication & Headphones

  • Talkback Mic & Button - Hold to talk to performers through their headphones.
  • Headphone Icon Headphone Volume 1 & 2 – Controls volume for each headphone output.

Power

  • POWER Switch - Turns the Scarlett on or off.