on my Mac 10.6 (MacBook Pro Late 2009) master volume control for both Line-In built and for external USB Microphone is disabled (grayed out)

![master volume control](https://i.stack.imgur.com/dSlVW.png)
Nobody really wanted to help what is the reason and how to bring back such behaviour. Googling didnt provide answer.

What I want is to have master volume slider active at least in Blue Yeti microphone.
Any help?