There is no way your GL2400 allows this, it doesn’t have DCA’s (or VCA’s as they would be in analog). It does have 4 subgroups.
The GLD will work the same way if you use subgroups. The difference is that the GL2400 has 4 mono groups that can be panned left and right to behave as “stereo” while the GLD does “true stereo” with the group being intrinsically stereo, so you’ll only have one fader and channel strip for it. You can also create mono groups which would work like your GL.
To use a stereo group:
Assign your mono input channels to a stereo group and unassign them from the LR mix. Pan them left and right as usual.
To use 2 mono groups:
Assign your mono input channels to one group each, a group for the left channels and a group for the right channels. Unassign the inputs from the LR mix. Go into the LR mix and pan the group receiving your left signals to the left and pan the group receiving your right signals to the right. You’d probably want to gang the settings on these groups.
Chris
