It shouldn't. Using the headphones out from the Dell utilizes their analogue out, which is pretty poor (I have one). Only thing I can think of is your DVD is pretty poor (like an Apex or something? I have an Apex hooked to Dac that I tried just for giggles-into Monarchy DIP/MF Dac3/PSU). The DVD/Dac should be much better than the mini out.
