When do I need to use "Preview"?

SWB Audio App has this "preview" option prominently at the top of its UI.

So, when do you need this, and when do you not?  I'm going to use the letters "SWBAA" to refer to SWB Audio App - less typing :)

Some scenarios

• [don't]: You're using OBS, which has the capability to "monitor" any audio track.  In this case; you probably dont need to preview in SWBAA.
• [do]: Your in a zoom call, recording your computer audio and maybe mic (via the route microphone option in SWBAA).  You probably do want preview. Otherwise you won't hear what's happening on your computer.
• [do]: Simple recording of video with QuickTime.  You do want preview enabled. Otherwise you cannot hear what's happening on your computer.

The Theme: 

"you cannot hear what's happening on your computer."

Start with:

1. Preview OFF.
2. Route microphone: OFF.

Setup your scenario, be it in OBS, Garageband, whatever.

Only enable the above options if you cannot get the necessary audio preview working.  By enabling it up front; without understanding if you actually need to, you may create a double "copy" of the computer audio, because some app you're using may already be offering preview functionality.

What is it?

Preview is simple.  All it does, is copy audio from the SWB Audio Capture device, to whatever device is selected in SWBAA. The device is specified right under the preview on/off checkbox. In the pic above, it's called "Default Device".

So. Imagine this.  You start up Garageband, and set it up so that it outputs audio to SWB Audio Capture driver.

Without preview; when you play notes in garageband; you won't hear anything. The audio is going into the driver and out the driver, but out to where? nowhere. 

What preview does is take the same audio, and play it through your speakers, so you can also hear it. It's still available out the other end of the driver, but it's also played through your speakers so you can hear it.

Here's a link to another article explaining how it works in Instant.

While the app name is different, and it's the older driver, the idea and concept is 100% identical, so it's still a very relevant video:

https://support.shinywhitebox.com/hc/en-us/articles/115000836912-How-does-iShowU-Capture-app-audio-