I was sure all the sound from my new computer had a reverb effect applied,
(despite all the audio enhancements being turned off).
So I generated a mono bleep in Audacity, and recorded it in stereo, (via stereo-mix).
Low & behold, reverb ...
(apart from latency, the red waveforms should be identical to the green original).
Now the bad news: this reverb effect is baked-in, ̶a̶ ̶d̶i̶f̶f̶e̶r̶e̶n̶t̶ ̶a̶u̶d̶i̶o̶-̶d̶r̶i̶v̶e̶r̶ ̶w̶i̶l̶l̶ ̶b̶e̶ ̶r̶e̶q̶u̶i̶r̶e̶d̶ ̶t̶o̶ ̶g̶e̶t̶ ̶r̶i̶d̶ ̶o̶f̶ ̶i̶t̶.̶