Just looked at SMSL M400.
Looks like a beast to me
Unfortunately, WAY OUT of my price league :-(
I have the E30 that I use as a pre so it outputs to my headphones directly via RCA to mini-jack 3.5mm adapter.
I have just listened to it with my AudioQuest Nighthawk...
All I can say is that I really like the sound that is coming out of this tiny little thing !!!
It is a delight to listen to the NightHawk with this one... And makes me hesitate to sell that headphone...
Will now listen to the Fidelio X2, the B&O H9i and B&W P7 "Wireless" (but in wired mode obviously...).
Regards.