I have a default config with the volume set to 127. The volume slider works, but at the max volume it is still to quiet to hear in every game. My 3DS and DS games are plenty loud, so my console isn't the issue.
Setting volume value to 255 seems to have fixed it for me. Would be great if this was better documented. There is no defined upper limit for the volume value in the documentation.
I have a default config with the volume set to 127. The volume slider works, but at the max volume it is still to quiet to hear in every game. My 3DS and DS games are plenty loud, so my console isn't the issue.