UPDATE: I tried the TB (tone board) with my Windows 10 PC and I got perfect playback from flacs to native DSD256 through foobar 2000. So the board is ok.
Then I tried a new Volumio setup on my Odroid C1+ and TB through USB. Perfect playback of flacs and DSD256 both with “none” mixer" and “hardware” mixer. DSDs playback wonderfully and volume is perfectly controlled from Volumio interface when in hardware mode! I had to resample setting only the sample rate to 384kHz otherwise I get “clicks”. “pops” and stuttering on DSD above 64.
Then I plugged it back to my main x86 Volumio player: same problems, ie no volume and white noise on DSD. So I tried a new Volumio installation though a USB key and voila, everything worked well!