PlanetZ forums - scopeusers.com

some say to record vocals MONO for better control or for eliminating phase.

ok but there something i do not understand.
the microphone is MONO.
but "scopes analog source" (mixers source to scopes environment) is STEREO!!!

consequently the DAW takes a stereo analog signal....... how then should i record it mono? is the solution to input only the Left Channel for instance?

Exactly. Your card may have 2 analog inputs, which we intuitively call L/R. But what would prevent you to use it as 2 mono inputs? There's no sense in putting the same signal over multiple connections!