Hi, 

My laptop is Dell XPS 15 9560. I recently have installed the Windows 10 update. After the installation, the sound level is significantly lower than before. 

There is also another with my headphone. My headphone is August EP650 Bluetooth Wireless. Before the update, I could increase and decrease the sound level of my Bluetooth headphone without affecting the sound level of the Windows. After the update, however, the Windows sound level increases/decreases when I increase/decrease the sound level of my headphone.

I appreciate any help.