Vox Studio does not provide a mixer (sound level adjustor) for your multimedia sound card. These software applets always come with the sound card itself and they get installed in Windows when you install the drivers for your card.
When installed they typically look like this in the System Tray on the Taskbar:
Mixers and volume control applets are often card-hardware-specific. The philosophy behind Vox Studio is to be card-independent. Use the specialized mixer applets that come with your card.
