I'm using an audio interface (Behringer UMC404HD) which can deliver a Phantom Power +48V with 4 XLR entries, 3 static mics and I want to add 2 mics for my accordion which also require a Phantom Power supply. I have a solution: I can connect them to the same (9V) battery power supply (JTS PS-500) and connect this box to the last entry of my audio interface.
My question is: would it damage something if I had Phantom Power supply coming from the audio interface & the external battery at the same time?