White cloud, is there a second switch for line out/DI out on the amp, if there is then it should be set to DI out then the pre setting should work.
The gains on the amp are not connected to the DI circuit so overload is not an issue, all you are sending is a low voltage signal which is balanced to the input, even then you can adjust the gain at the desk so how can anyone overload the active units?
I still think he talking out his a****.