Someone else mentioned the poor quality of the headphone jack in receivers, but I want to mention it's possible to connect your headphones directly to the speaker ports with the 4 pin speaker connectors to 4 pin XLR to your headphones because you have low sensitivity planars. Granted you need to make sure your receiver has low enough power output to not blow the drivers at your headphones' impedance. I did this with my old HE-500 and the Emotiva miniX a-100 receiver, which you can see someone mentioned in detail how to do here:
https://www.head-fi.org/threads/diy-emotiva-mini-x-a-100-headphone-amp-mod-guide.705196/
AKG K1000 and its spiritual successors like the MySphere