14.Can the headphones out and line out work at the same time? Is the line out output amplitude adjustable? Can it be used as a pre-AMP?

The headphones out and line out can work at the same time, and the amplitude can be adjusted. However, the line out output is up to 2Vrms. It is possible to connect an integrated amplifier or an active speaker, but it is not enough to use with the pure power stage amplifier as the preamp.