
Main and Moni are output for monitor and for another function but they are always signals. Never power. The power or the enhanced part of the console is for the connection of speakers. On the other hand there could not be a boosted channel without load because yes. Always connect with very low levels or volume.
That is why I provide the user manual to read the instructions for use and you have no doubts, if you read point 10 of the manual you will realize that this is the connection indicated for audio output "line" to an amplifier and other devices external
If the power output is set correctly, it is indicated in point 11 of the user manual as speakers, if you still have doubts about the terminal that you indicated it is easy to clear them by connecting one of the speakers in the terminal that indicates, but listen with power The sound is because the signal is minimal and it is to connect other devices as indicated.
Another audio connection is the one indicated as rec out on the front of the console.