Hi Steve
No I’m afraid you cannot send an output to an input socket on the GLD.
In the I/O page the input socket window allows you to choose where the physical socket is routed to within the desk.
For example if you selected input socket 1 on the AR2412 by default it will normally be routed to input DSP channel 1, though you can also send it to mono matrix External input. this means that input socket 1 on the AR2412 will be routed to the external input of mono matrix 1 you will be able to check this by selecting mono matrix 1 and viewing the external input page.
So you are choosing where the physical socket is being routed to in the DSP.
Hope that helps
Regards
Sam A&H