hmm, do we have access to the kernel sources used?
it appears to me, we're using an older version of the codec code....
so for lineout, the PCM volume you are talking about, is the DAC volume (digital) which then feeds into two separate analog gain stages, one for headphone (which is the headphone level you see in alsa) and the other for line out.
in later versions of the kernel (>jul 12 2016) a separate alsa control was added for line out volume which allows control of the analog gain stage.
(the default of this prior to this change was initially defaulted quite low, but then a change was made to improve it... but without knowing which version of the code was used for the kernel - i dont know which is in use)
interestingly, a bit of googlefu, says that yes if you push the DAC volume too hard, you'll get distortion, what you want to do is get the right amount of analog gain after it.
does beg the question ... has anyone tried to update the organelle to a later OS? using pacman -Syu .
from the digging ive done so far, doesn't seem like it would cause an issue... i could try with a spare system image i have or is this a bad idea?
EDIT: and to be complete, capture volume (cvolume) is the analog gain on the input to the ADC... so id assume that can be pushed.
(later kernel versions also have controls for the codecs avc, bass enhancer and eq)