After contacting support, it has been made clear that the audio device is under the windows “USB audio 2.0” specification so it will work only on windows 10 after release 1703. There could be some workarounds but it seems this native driver [usbaudio2.sys] cannot be installed in a previous generation OS, but I am not sure. To sum up, overbridge for windows 7 works OK, new class driver, for anything it can offer, it needs windows 10.