Use the Line In Audio Input on a Mac.
Every Mac device comes with a microphone built into the product, but you’ll also find another port for input and output of audio – the headphone jack. That is, of course, until Apple decides to make this feature an expensive add-on!
Until then, however, you can use this port to connect line-in audio input devices such as external microphones to your Mac. macOS lets you toggle the assignment of the headphone jack to receive input devices, and set any connected device as the default input device.
Here’s how to use audio line-in devices on macOS.
What is the line in the sound?
The audio line-in connector on a device allows you to input sounds to that device. This is in contrast to the typical audio-out (or line-out) jack that you can use to play sounds from your PC on external devices such as a speaker system.
You can also have a microphone jack on your PC. This is usually a weaker version of the regular line jack, as microphone input levels are usually much lower than other types of input devices such as audio amplifiers. Standard line jacks can also be referred to as microphone jacks – there is not much difference between them.
Either way, on a Mac, you don’t need to worry about the differences. Older Mac devices had a separate line-in jack that could be used for all audio input devices (including external microphones), and an audio-out jack for headphones and speakers. In modern Macs, this has been reduced to one switchable connector that allows any one to be used.
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You will need to use the macOS system preferences menu to tell macOS to use that audio port for audio input, rather than an internal device like the built-in microphone.
Using macOS audio input devices
As we mentioned, modern Mac devices only have one audio jack, which can be used for both input and output devices. To use it for audio line-in, you need access to macOS System Preferences.
- To do this, click the Apple icon in the upper left corner of your Mac screen. From there click on System Preferences. You can also click the System Preferences icon in the Dock to launch it.
- In the System Preferences window, click the Sound icon to enter sound preferences for macOS.
- By default, the Sound window displays the Output tab by default. You will need to click on the Input tab to change the audio line input settings.
- To start using a line-in device, you need to select it as your audio input device on the Input tab. This may look different depending on your Mac model. For example, on a 2019 MacBook, an external microphone is identified using the microphone port, but on older devices, it may be listed as an audio line-in port.
macOS might also switch to this device automatically, but if it didn’t, click the device to select it from the Select a device to input sound list.
Configure audio input devices on macOS
After activating the external audio line-in device, you can start using it. However, before doing this, you can adjust the volume as well as other parameters such as the audio sample rate.
The input volume settings are displayed immediately below the Select a device for audio input list in the Audio Settings menu. You can access it by clicking the Apple icon System Preferences Sound Input.
- The input volume slider allows you to change the volume of the input sound. For example, lowering the volume of the external microphone would lower the volume of any recorded audio. Use the trackpad or mouse to move the slider to the left to decrease the volume, or to the right to increase it. Any sounds detected will appear visually in the input level bar below it.
- You can also use the Audio MIDI Setup application to make more complex changes to your external audio input devices. This is the main macOS application and can be found by clicking the Launchpad icon in the Dock, clicking the Other folder, and then clicking the Audio MIDI Setup icon to launch the application.
- To change the audio line input settings, click an external device in the list to the left of the Audio MIDI setup screen.
- On the right, you will see various sound options. You can change the audio sampling rate (displayed in hertz) from the Format drop-down menu. You can also change the input volume of your device here in the Master Stream section. Use your mouse or trackpad to move the slider left to decrease or right to increase.
You will be able to see the current volume value (indicated in decibels) as well as the input volume (decimal number, maximum 1) next to the Master Volume slider for your device.
You may also have additional controls and settings available depending on the type of device you are using. Some audio input devices may also come with their own control software to further calibrate the input parameters.
Use external devices on recent macOS devices
There is no guarantee that the headphone jack will remain a built-in feature in future Macs, but while it’s still there, you can use it to connect external audio input devices without an expensive adapter. You can use it, for example, to record using two different microphones in GarageBand.
You can also use the audio line-in jack to record the instrument on macOS. If you are interested in music production, there is no limit. Let us know how you use external line level audio devices in the comments section below.
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