I've gotten myself a Steinberg UR22mk2 USB audio interface. After plugging it into my Linux system (Kubuntu 17.04 with kernel 4.10.0) it is automatically and correctly detected.
The problem I have is: whenever
an certain applications (re) opens an audio output channel and plays back audio via the UR22mk2 with the earphones connected to it, there's an unwanted and slow audio fade in. It happens in Kdenlive, but neither VLC nor Audacity.
This is very annoying when editing video+audio in Kdenlive, because whenever stopping playback and restarting it in order to find the correct cut positions, the automatic audio fade in kicks in and makes editing unusable with the Steinberg. My Behringer QX1202USB doesn't exhibit this behavior. However, both seem to use the same stock USB audio Linux kernel module.
This only happens with the Steinberg UR22mk2 USB audio interface, but not with other USB audio interfaces, such as my Behringer UX1202USB audio interface. This is not a hardware feature, but software: when I connect the UR22mk2 to an Android tablet, there's no audio fade-in, but the audio playback is immediately present as it should.
Is there a hidden (and probably not well-documented) driver setting for the UR22mk2 to disable this audio fade in? Or is there some Linux audio system setting(s)? I've looked around and searched and searched ... but to no avail so far.