Master volume newbie question

  • Sorry for what is probably a very simple question but I just received my kemper and have started going through some of the rigs. I have the main 1/4 output L/R going into my matrix gt1000fx and then into 2 cabs. I have been toggling the cab button off since I am going into the real cabs.

    My question is, I noticed the volume knob allows me to gain more volume but turning the master volume seems to have no impact....should it? Or is it only for controlling headphone volume etc?

    Thanks
    D