When I play a commercial audio via the mediaplayer I have to reduce its output gain with 3db to prevent clipping…
In WIndows there’s a volume mixer, which I assume only affects the total output, e.g. to a sound card directly from an app/program, though I’m not sure. In Windows 7 you can get to it by right clicking the speaker icon on the task bar then choosing Open Volume Mixer. It’s probably similar in 10 and 11. I often forget that’s there and the setting persists, at least until a reboot. If the media player level’s not on full, the direct output may be lower than the input that’s fed to Cantabile, or maybe it affects both. You could experiment with that to see if you can get a better match.
MP3 recordings often seem to be compressed in dynamic range and probably gain normalised to use as much of the top of the range as possible, so I expect they’re close to clipping already and it doesn’t take much to make them clip.