What’s Causing this Odd Clipping?

Windows 10. Audacity 3.0.2. I’m using Audacity to record the audio track for a PowerPoint presentation. I’m using a Marantz MPM-1000 microphone connected to a Focusrite Scarlett Solo (3rd Gen) microphone-USB interface on an up-to-date Windows 10 computer. Here’s an image of the audio track with me speaking at normal volume on the left and close to microphone on the right:
Note the “clipping” of the signal on the right at roughly 0.5 on the vertical scale. This clipping wasn’t present earlier, so something in my setup has changed. But though I’ve thought carefully, I can’t figure out what’s happened. View > Show clipping is on, but there are no red lines because the signal never exceeds 0.5 on the vertical scale. In Windows key > Sound > Input > Device Properties the Volume is set at 100. In the Focusrite box the input level control is set at the maximum (fully clockwise). Can you suggest why the signal in Audacity never exceeds 0.5? Thank you for your help.

The issue is that when you record in mono with a “stereo” interface the microphone and guitar inputs are combined. The combined signal is cut in half so the mic and guitar can both go near clipping without clipping the combined-summed mono signal.

You can use Audacity’s Amplify effect to boost the volume after recording. (You’ll probably be adjusting the volume anyway). Or, you can record in stereo and then delete the silent channel to make a mono file.

The clipping indicator on the Scarlett should be showing clipping because you are clipping the analog-to-digital converter in the interface.

Hello DVDdoug,

Thank you. That solves the problem perfectly.

Will there be a difference in quality depending on whether I record in mono (and then use the Amplify effect) or record in stereo and delete the “guitar” track?

The stereo pathway doesn’t go through the half and double business, so technically, that’s the best way. Still, that’s only 6dB out of some 96dB of loudness range, so nobody is going to stop breathing either way.

In all cases, you should pay attention to the Volume and Overload indicators on your device. Do you have knobs that change color? Keep them green for most of the work and if you start getting red, back off the volume and re-record that last bit.