Mac
This is a Samsung NP550P7C Laptop with an Intel I7 processor and it's running Windows 8.1( which itself has something to be desired). The sound system onboard is Realtec High Definition Audio.
There is a speaker icon on the status bar which allows you to set volume levels. Within that there is a "Mixer" you can click on but all that allows you to control are "Application volume controls for output". Just a volume for playback as far as I can tell.
In the Windows Control Panel there is an application called Realtek HD Audio Manager which allows you to configure your speakers and microphone. I can set the recording volume for the microphone here but nothing else. Even the " Device Advanced Settings" in that application doesn't offer anything.
There is a "Sound" utility within control panel with options for playback and recording. In the Recording tab I see three devices, my m-track, the microphone and stereo mix. I can't see anything in the mic or stereo mix tabs that allow me to set record levels for anything, just balance.
I am familiar with the type of mixer you are talking about but I am yet to find it on this machine. Someone did a good job of tucking it away somewhere.