There is some DC offset on the output that can be blocked, as many amps do, with a capacitor but the capacitor introduces something else into the audio chain. Some op amps have no offset, some do, some amps are designed so they have none and some do. iBasso has stated that they aren't going to change this as it would degrade the sound, in their opinion. I just plug my phones in after the DX is turned on and unplug them when turning off, well for IEM's, for my regular headphones I don't worry about it.
Edited by jamato8 - 4/24/13 at 7:23pm