hey jessie. i have the older vertical daking modules that have an input gain AND and output trim control...not sure if the new ones have that. i use them a few different ways. i have rolls summing box that recieves 16ch from my d-a....i make up the gain (the output of the rolls) with a pair of dakings...in this case...they are usually set on the mic input...and i adjust the mic input gain depending on what kind of sound i want...sometimes hitting the input transformers really hard. when i am mixing on a console..i often just send the stereo buss output of the desk...or whatever stereo comp i am using...into the dakings at line level....it really depends on the console you are using and your stereo buss chain. in general, if you are coming out of a console, or out of set of converters from your daw...you probably want to be in LINE mode on the dakings.