Well, the voltage difference is huge, I'm running the wm8716 with no output stage (direct out) which with 5V supply produces humlbe 1V RMS of output, while ODAc has 2V as in redbook standard. I couldnt do a quick switch because every time I had to adjust the volme by ear to hear anything in one casae, or not to blow my ears in the other. Still, the DACs were very close if not identical, and that's surprising cinsidering that wm8716 was never meant for any ambitious audiophile stuff.
It's probably due to the amp and cans being not resolving enough but then again what gear is needed to discern sources that should clearly vary in quality.
People tend to put much too much importance on source disregarding upstream equipment.