Yes, you are right. The volume switching in DOS1 was something to consider. I have only tested DOS2 with UPnP and Optical so far but it seems that UPnP volume is synchronized with the Devialet App volume. In practical terms that means, whatever volume I set in the UpNp/OpenHome app will be the same as I would see in the Devialet App. This works instantly, e.g. I have Linn Kazoo open on my Mac and when I change volume I would see that instantly in the Devialet app. I did not encounter any issues with volume changes to "too loud" when switching from one source to the other so far.
Innuos Zen Mini MK3 -> (Ethernet / Audioquest Optical) -> Dialog & 2x White Phantom
Pro-Ject Carbon Debut Esprit Turntable with Ortofon Red -> (Cinch/RCA) Musical Fidelity Merlin -> (AudioQuest Optical) to Phantom
Master & Dynamics MH40, Audeze Sine, AudioQuest Dragonfly Red; Remote Control via macOS and iOS devices (Devialet App / Innuos Sense /iPeng / Audirvāna Studio)
