Question

Rml32ai---CHannels 31 and 32  no longer have the pre agin control---it has switched to d.gain   not sure what that means

Answer 1

I am unfamiliar with all the features of the rml series mixers.  However, I run a studio live series 3 mixer.  The D stands for digital.  What this means is that those channels do not have their own dedicated physical preamps.  So, they utilize digital gain rather than preamp gain.   More than likely they also have a much more limited range.   Hope that answered your question.