The PXC 450 have a bypass switch that completely disables the noise cancellation circuitry and lets you use them as regular headphones without batteries. They actually sound pretty good like that with the A5!

Ahh yeah, I didn't consider that it might not work with my phone at all. I just got a response from Schiit about the power draw, indeed the DAC module gets its power from the USB device. Thanks for the advice about headphones, I'll stick with the Alpen/A5 and put that money toward better...

Hi there, I'm currently using an Alpen 2/A5 combo with a pair of Sennheisers PXC 450 for two things: HiFi Tidal on my Nexus 6P, and SoundWire also on the 6P to watch TV with. I'm considering getting a Jotunheim with the DAC module for the latter as a permanent fixture in my living room so I...