Lately i have seen several posts about low volume and i have now found something quite surprising.
Audacity can influence the general sound-output!
It looks like Audacity makes a direct connection to the output-device, meaning that the changes made in audacity, will be global for that device, also after Audacity has been closed!
In general i think Audacity has all MS capable output devices, and adds a number of devices depending on the installed soundcard.
That is a problem in it self, because my findings, as well as the solutions, may only be valid for RealTech soundcards!
What i have seen in Audacity is that low volume can occur in two different ways:
1) Output is mapped to empty microphone setting.
This i really think is a bug!
The select for MIC can go empty!
If that happens only about 1/4 of the default sound will be in output
The solution is to 'populate' the empty select!

2) Low output is selected for default output-device (soundcard specific)
Audacity has 2 sliders for volume
One for input, and one for output
The output slider seams to be directly mapped to default device!
If the slider is at a low level, the global output is significantly lowered.
The solution is to set the slider at high value.

It would be interesting to know if some of the issues with low lmms- output volume, actually has this origin