Integrated 3.5mm jack master volume

Hi!

I have been struggeling with this all day long with no success.

I would like to play Google TTS via integrated 3.5mm jack connected to small speaker. It works through installed MPD but the voice is too silent. I have read that it is possible to control master volume via alsamixer but I have no luck doing so on my hass.io.

Am I doing something wrong?

Thank you,

Lukas