This is the test curve for my 8XX from Sennheiser.

How hard is it to add play / stop / forward function?

I will be putting all my though on paper soon.

700 is a lot easier to live with compare to 800 OG. People just expected too much.

OG 800 isn't a headphone easy to live with.

Tube and upgrade parts always sold separately. Victor has 8900 with the stock opt in hand and ready to ship. His diyaudio user name is Vkung

Make me wonder why I spent so much money on other phono amp. My search for phono stop here (for now, lol)

Just chatted with Victor, he has couples 8900 just not the Lundahl opt. It is cheaper to ship the 8900 with the Lundahl opt together, that's all. For my experience, Lundahl is a must have.

Have you contact Victor?

Short answer, 8XX is a better headphone, great with tube but not forgiving at all. I will treat the 8XX as my "HIFI" headphone for now since I always found the 800 OG (sold) is not easy to live with. I need to spend time with my vinyl and compare the 8XX to the Focal Elex also. My own...

660S is my daily since I listen to odd/live concert on youtube most of the time.

At the "forgiving" department, 8XX is much better than the 800 OG. But still need really good source.

Received mine. Just like the original HD800, the placement of the earpiece will change the sound by a lot.

Every company has their "policy". I understand how you feel. Maybe you should go to DIYAUDIO https://www.diyaudio.com/forums/elekit/ and talk to Victor. He is the North America dealer for Elekit.