Problem report: SOLVED. I submit this for your interest:
---------------------------------------------------------

All of a sudden, I noticed I was recording everything in mono using only the input from the left channel to create a duplicate right channel. Playback was in stereo; only what was recorded new was in mono.

I checked all connections, levels, panning and settings on the various equipment and couldn't solve it. I could mention the equipment but it isn't relevant, as the solution turned out to be a setting in Windows.

While I'm a big fan of Windows 10, this one had me stumped awhile.

I finally thought to check the Control Panel, Sound, Recording, Microphone, Advanced settings. Somehow, not by me, this had changed from 2 channel to 1 channel! I restored it to 2 channel, 16 bit, 44,100 samples and the problem was fixed.

Nowhere else could I access this setting except through the Control Panel.

What changed it? Sunspots? My money is on an automatic Windows 10 update, which is why I'm posting here in case anyone else has this happen to them.

Carry on.

BIAB 2025 Win Audiophile. Software: Studio One 7 Pro, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Roland Integra-7, Presonus 192 & Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors.