pine64-pinephone: lower headphone volume to 70%

Merged Oliver Smith requested to merge volume-70 into master

We used to have it at 40% and just bumped it to 100% (!2170 (merged)). With 100%, I can hear static noise in the headphones when using the PinePhone (pmOS CE) in a silent room, even if I turn the volume down in Pulseaudio (e.g. 18%-30% in Phosh). This was not the case when we had it at 40%.

70% seems to be the sweet spot, where no static noise can be heard when using headphones in a silent room, but where volume can still be turned up to a very high level if necessary.

FWIW, mobian and manjaro appear to have it at 100%:

Would be nice if others could test this as well. Do you also get static noise in a quiet room with 100%, and is it gone with 70%? I did not test this on PineTab (don't have one), but I assume it behaves the same.

EDIT: to clarify, I hear static noise when playing media such as podcasts. There are no static noises when nothing is playing.

Edited by Oliver Smith