Hey great choice on the Dehavilland, I almost purchased one myself a few years back, went with a Manley Labs instead. If you plug your output into a headphone amplifier, you will have to play with 2 volume controls and its not an optimal situation for headphones, My Manley pre amp offers no monitor loop (rec/out) type output only a main output which runs through the volume knob as well. I tried it once with my Antique audio labs headphone amp and it worked, once i had the dual volumes dialed in right. Good Luck
Matt