The Soundcraft Notepad series of mixers is a fantastic companion for podcasters and streamers. The newest update for the Notepad mixer’s software includes a ducking feature that can duck music or audio being played from the computer while one or more microphones are active in your stream. We’re going to walk through this simple setup, so you have another tool to keep your audience hearing you clearly. In this example, I’ll be using a Windows computer along with OBS Studio, but these concepts will transfer to other broadcasting and conferencing applications. Before getting started, make sure to download the most recent version of the Soundcraft USB Control Panel from Soundcraft.com. Links will be in the description below. 
Once the newest driver and Control Panel have been installed, make sure that the mixer is set to your computer’s default audio device.  In Windows, this can be done by clicking the speaker icon in the bottom right of your Taskbar. The mixer should also show in the Soundcraft USB Control Panel appropriately as a Notepad mixer. If you can’t find your mixer in either of these locations, try disconnecting the mixer, restarting your computer, and trying to install the drivers again. Let’s set up the Ducking in the Soundcraft USB Control Panel first. Select the Audio Routing Tab. This is where we define what our Inputs are, and Notepad 12fx mixers will have additional options for inputs 3 and 4. For our example, I’ve got my microphone connected to input number 1 on the mixer. This means for my inputs, I want to have selected “Mic Input 1+2”.
Next is the Ducker tab. Turn on the Ducker using this toggle in the top left. With the ducker on, this first section is to select which of our inputs will trigger the ducking. Remember that the selected sources will only duck the digital audio from our computer, and not the other microphone or line sources connected to the mixer’s physical inputs.  My microphone is on input 1, so select “Input 1” here. Now, notice that the meter here has started to register signal from the microphone. The next section is the Ducker settings. Threshold is the level that the microphone must hit to duck the computer audio. Speak into your microphone to check the levels and take note of where the meter is registering on average. We can see as I speak into the microphone, the meter is registering constantly in the -20db range while I’m speaking. When I’m not speaking, the microphone is registering anywhere from -80 to -70db. This means I want the threshold to be above this idle level so background noise doesn’t trigger the ducking, but still high enough that my voice will trigger it when normally speaking. This default -30dB threshold is a good setting for me, because my normal talking level is above -30db. Not all microphones and voices are the same, so this might be the trickiest part of the setup. 
The Duck Range is how many dB of reduction will be applied to the computer audio. The default setting might be appropriate for most applications in which you might still want to hear some of the computer music in the background, like for Gaming. Less reduction means less of the ducking effect, so a setting of 0dB is effectively disabling the ducker, while a setting of 90dB would cut out the computer audio completely in most cases. Release is the time that it takes for the computer audio to return to normal volume after the microphone falls below the threshold. The default of 2 seconds will probably be good for most applications, but you may need to adjust if you find the computer audio is coming back too quickly or not quick enough. I’m going to leave this at the default for now. 
Let’s set my mixer up now in OBS Studio. In OBS, I’ve already crated a new Scene, and the only capture source is the VLC Player window. In the Audio Mixer section, select your audio capture source. In this example, I’m using the default Desktop Audio. Click the additional options, then select Properties. This is where we select the audio device. For this example, we set the computer’s default audio device to be the Notepad Mixer, so we can leave this as Default. Click OK, then speaking into the microphone should now show signal. All that’s left is to test the ducker. You can Start Recording here to test your ducker and listen back later, or connecting your headphones to the Notepad’s headphone output will allow you to monitor in real time. Let’s play this audio file I’ve got loaded. Now when I speak into the microphone, notice that the background music will duck until I stop speaking, at which point it will take around 2 seconds to resume back to normal volume. Remember that whether you’re gaming, DJ’ing, or just speaking, the application should be playing its audio to the Mixer. This will keep everything in your ears while connected to the Notepad’s headphone connection.