Short answer: No you won't break anything.Question regarding the 887 amp. Is it ok to uses the 6.5 and 3.5 mm SE output at same time ??? Can it broke anything ?
im connected to the 1/4 inche with my dt1990 but i my gf wanna listen to her x2hr using the 3.5mm output at same time ...
I know gain should be a problem but we will figure a middle volume for both of us.
im just scared to plug both at same time and something would go boom
Realistic answer: as both of your headphones are open back you are likely to hear a bit of sound bleed from the other pair not being listened. It's probably not realistic. But it won't break anything.