Hello again. I apologize in advance for the bubble burst:
QC’s Outputs 1 & 2 are set for a maximum +9.5 dBu output, which is more than enough to drive signal to audio systems which operate at +4 dBu (mixing consoles, other audio interfaces, studio monitors, etc.).
Outputs 3 & 4 when balanced are set at a maximum of +15.5 dBu, and a maximum of +9.5 dBu when unbalanced.
There are other discussions in this forum which get into really subjective territory–“QC is not as loud as my Helix”, “I need more louder”, etc. But I think if you’re properly gain staging through your preset(s), you should get signal that is plenty loud enough to drive whatever it is you need.
From an engineering / hardware standpoint, it may not be possible to increase the level of Outputs 1 & 2 as it is. The circuit board may have been designed with certain output driver ICs which simply cannot go up an additional +6 dB. Nor would I expect it to.
Here’s an interesting thread where a user discovered that they needed to use XLR-to-XLR cables with their system rather than XLR-to-TRS. [I use XLR-to-TRS with no issues.]
EDIT: dBu values updated for clarity, thanks SoundEngine for correcting me.