Recommended Output Levels?

I really like the sound of my KPA at home using monitor out to CLR, but when I tried it at Church using Left Main Out, it sounded harsh and "digital," so I had to go back to a mic'd amp. I told the Sound Engineer it was an "instrument" assuming it would be set to line, and EQ'd flat but I'm not sure what they did, or if something I did? I typically run M Britt /13, Matchless, clean to edge of break-up profiles. Could it be the "Master Volume" or one of the "Output Volume" settings I see after pressing the "Master Button" on the upper right? Thanks in Advance!