[stevegalante]

Originally Posted by Table Syrup Records

Maybe try reinstalling the HD Drivers?

Also, from Digitest, did you check for firmware updates?

Maybe reset SMC and PRAM?

Only things I can really think of.

Thanks, in the end I've been able to make it kind-of work...
Basically there's a series on incompatibilities between the Avid HD drivers
and Yosemite (not tried on Mavericks yet), so to make it work what I have to do is :
close everything (PT, AMS, CoreAudio Manager) and open Avid CoreAudio Manager.
At that point my HD Native card is always listed as "unsupported device" but all the I/O channels are selectable and usable from within other softwares (tried on Arc2 and Studio One).
Gonna try what happens in Mavericks.