I would say the XD-05 gives a cleaner and clearer detailed sound rather than warm one. I am not an expert by any means so describing it the best I can. When listening to the XDuoo X3 this player has a clean and detailed sound and the same can be said about the XD-05 but a fuller stage. It is like how sound would come across if Spock could tell you about music, clean to the point and nothing missed. I have fed it through a valve amp and the warmth you can notice but on its own very analytical but loosing detail from any of the ranges. The bass boost can be turned on and you notice it but it manages not to spill over at all into the mid range. Again it depends on the headphones also, I use the BeyerDynamic DT990 Pro 250ohm mainly but otherwise the Soundmagic PL21 on ear. I do use my Koss Porta Pro with the X3 while walking to work and that can sound really warm but that is just the headphones.