I use mine to return outboard or side mixer and laptop in from headphone socket
In the case shown below the QU16 is feeding into the QU32 ST1.
Laptop feeding ST2
Subs are passively Joined by Resistors out of Group 9/10.
There is enough gain to take a microphone.
I’m not sure if the impedance is correct for taking an Acoustic /electric guitar?
I should look up the specs?
Creative audio!?