RPI + HifBerry DAC+ + MPC volume control

Hello guys,

my setup is a Raspberry Pi with HifiBerry DAC+ (with analogue stereo chinch output).
I would like to control Volumio with mpc (mpd client)

Ease example: mpc command in shell command line. (e.g. mpc volume 50)

With default settings after installation, it works principally, but the control is not linear.

mpc volume 50 -> almost nothing to hear
mpc volume 75 -> a little more
mpc volume 80 -> loud
mpc volume 100 -> very loud

I would like to have a linear control with mpc. There is a setting (natural vs. linar), but this does not have any effect.

Could you maybe help me?

Thank you,

I had quite the similar problem with Volumio 1.55:


But things are totally different now with Volumio2