Turn off noise cancellation on the PC for the capture card. On PC that's usually Windows Audio Enhancements.
Windows Audio Enhancements can be located in one of two places depending on your version and build of Windows.
First, you can check if enhancements are on by going into modern Windows Settings and checking under System > Sound and find your capture card. Go into it, and check at the bottom for any mention of audio enhancements or spatial audio (usually towards the bottom) and turn them off.
If audio enhancements aren't there there, check the old Windows Sound Settings instead. Press Windows Key + R, type mmsys.cpl in the box that comes up and press OK. Go to the recording tab, find the capture card then go to properties. Check for any enhancement or spatial audio tabs and disable anything in there, and check the advanced tab to see if there's any enhancements or spatial audio options to turn off there as well.
Based on your audio hardware, software and Windows version and updates, enhancements could be in either of these locations, both or none. If they're not in any of them, you can assume enhancements are off - though you may also want to check if your system shipped with any other audio apps that might be applying effects without using it (most use the Windows options for it, but not all).