# Pass-Thru Devices

Without any configuration, a Loopback virtual audio device will function as both an audio input and an audio output device, enabling audio to be piped through it. We refer to this as as a “pass-thru device”. Using a device as a pass-thru, you can send audio directly from one application to another. Some users may have previously used the tool “Soundflower” in this capacity. Loopback modernizes the necessary infrastructure, providing a reliable method of passing audio directly between applications.

To send audio out of an application, select your pass-thru device as the audio output device in the sending application. To receive audio into an application, select the pass-thru device as the audio input device, in your receiving application. Read on for more details.

### Creating a Pass-Thru Device

All Loopback virtual audio device can function as a pass-thru device. To make a new one, simply click the “New Virtual Device” button in the device list on the left side of the window. You can give it a name like “Pass-Thru”, as we've done here, but that's the extent of configuration that's required inside of Loopback.

A Simple Device Ready for Pass-Thru

Like all Loopback devices, this pass-thru will appear on the system as both an audio output and an audio input. Any application with an audio output selector can feed audio into the pass-thru device, while any application with an audio input selector can pull it out.

### Adding Audio to the Pass-Thru

To add audio to a pass-thru device, select it from the audio output selector inside the desired source application. Below, we sent audio into the device by adjusting an Output block in our audio recording tool Audio Hijack.

Audio Hijack setting “Pass-Thru” as an audio output device

With this setting, audio from the Audio Hijack Session in question will be sent into the pass-thru device.

### Receiving Audio From the Pass-Thru

To receive audio from the pass-thru device, just select “Pass-Thru” as the audio input inside the desired source application. Now any audio being sent to “Pass-Thru” will be pulled in by your application.

Nicecast Selecting “Pass-Thru” Hello as Its Audio Input

Above, we've set our Internet radio broadcaster Nicecast to pull audio out of the pass-thru device.

### Adjusting the Channel Count

If you desire, you can add and remove channels from this pass-thru device. By default, with Channel Mapping in “Automatic” mode, the device will have two channels. If you toggle the Channel Mapping to “Manual” mode, you can configure the device to have between 1 and 32 channels.

A Pass-Thru Device With 8 Channels