I was asked, privately, about synergy between the CYAN and the HD650, so figured I’d share those thoughts here as well …
The CYAN is a very enjoyable pairing with the HD650. The smooth top-end of the CYAN yields a very satisfying and consistently grain-free delivery. There’s still a little mid-bass bloom. Otherwise the tonal presentation is quite pure, excepting some early roll-off in NOS mode and the general sense of sweetness that this also imbues to music. They deliver pretty much as hard a punch as you’re going to get out of them (outside serious tube stuff). Detail retrieval is excellent and the overall presentation is a lot more open than one might expect with the HD650.
If you have original HD650 (2003 to about 2015, I think), and hear any “veil” with them, that’ll get exacerbated slightly - and that will be noticeable more in NOS mode. Not a concern with newer units, nor for those that have performed the more common modifications and/or are running with the latest pads. And putting it in OS mode will help there too.
I also found it works really nicely with the HD660S … where my preference was very definitely to run it in NOS mode. Though that’s something of a redundant statement as that was my generally preferred way to run the unit anyway.