the upgrade to Armbian worked for me from Bananian 15.04 Wheezy with Openmediavault 2 on Banana Pro without problems. The sources from Bananian were deleted automatically.
I've just followed Igor instructions.
Now I've Linux bananapi 3.4.110 sun7i.
I needed Sunxi sndi2s driver for my Beaunanas (a Banana Nas server boxed in a French Burgondy Beaune wine bottle box in wood ) to make working my DAC with MPD, missed driver on Bananian 15.04.