Could you point me to the commands to use? I haven't used a Linux command line in some time but I want to give this a try.
You will need to install Alsamixer from the Play Store (BusyBox may also have the alsa commands but I'm not sure as I always install Alsamixer).
In a terminal type:-
su
alsa_aplay -l
This will list the audio devices available on your phone, if you connected the Dragonfly after booting the phone you will probably find that it is 'Card 1'. You will need this for next bit.
In a terminal type:-
su
alsa_amixer -c1 set PCM 100%
The '-c1' flag points to the Dragonfly and assumes it is 'Card 1' change the '-c1' flag to a different number depending on the number of your card.
You can also change the PCM setting, you could use a percentage or a number on the DFB the volume settings are from 0-64 so you could use PCM 32 for example which would be the same at 50%.
The volume buttons on the phone still work to change the volume but they don't affect the internal hardware of the Dragonfly so they act like software volume controls.
I personally prefer to set the Android volume controls to 100% and then adjust the output volume with the internal volume on the Dragonfly. I have been using '$cripter' from the Play Store as an easy way to control the Dragonfly Volume by running scripts on demand.
Hope that helps.