New user - cannot record from "stereo Mix"

Audacity works beautifully on mp3 files and CDs. But when I attempt to record from an internal feed (ie Stereo Mix) on my computer (internet radio), I get only about one second of sound, then endless repetitions, often decreasing over time in volume. Like an echo or a loop. I know these functions exist in Audacity, but don’t see how they could be active during recording, or toggled on or off. Couldn’t find anything relevant in the forum search or FAQs. So it most be some rookie mistake I’ve made in setting up. All suggestions welcome - thanks! Perryb

Audacity 2.2.2, Windows 7

Turn off [u]Software Playthrough[/u].

…With Playthrough you’re listening to what was just recorded, and with Stereo Mix you are recording what you’re listening to so it creates a feedback-loop.

Thank you! All I needed to know was where to look.