Stock, the person who gave it to me didnt mention it was modded or anything so im assuming it is stock.
I owned the D3 before and I loved the hell out of it. I've never used the D4 but all I can say is the D1 doesn't have a good enough amp to do what I want unless its plugged into the USB on my computer. I had hoped its portable strength and wall adapter strength would be to my liking but I cant complain since it was a gift to me. I just tried to list it here for sale today but I just cant sell a gift someone gave me, doesn't seem right to me.
But ya, the D1 doesn't amp my Philips HP 1000 well. Its a real pain because the D1 sounds just the way I like things to sound. Its more clear than the D3 and smooths the bass out nicely lol. I dont really have the funding to buy a true amp to go along with it. I was hoping one of the other ibassos for the same price range would do a nicer job while still letting me use the usb feature.