What I do when I mess around with this stuff is that I launch "alsamixer" and then I press TAB to switch to the capture related mixer controllers and the finally I use arrow keys to adjust "capture" volume and I use CTRL-C to exit.
What I do when I mess around with this stuff is that I launch "alsamixer" and then I press TAB to switch to the capture related mixer controllers and the finally I use arrow keys to adjust "capture" volume and I use CTRL-C to exit.