It's kind of a blog if you don't think about it too hard
May 16, 2015
tl;dr: Install the hotkey drivers.
I noticed soon after installing Windows 7 on my new laptop (Eurocom Shark 4) that I was sometimes getting no sound from my headphones. The Realtek control panel faithfully reported that the jack was connected, and muted the speakers as expected, yet no sound could be heard through the headphones. I experienced this problem on both Windows and Linux (Ubuntu 14.04), so I assumed it was a hardware or firmware problem.
However, after a bunch of futile Googling and tinkering, I noticed a pattern - it always worked on a clean boot, but not after resuming from sleep mode. This led me to refine my search terms, bringing me to this discussion. It turns out that the headphone jack needs to be reinitialized after system resume, and (for some reason I cannot fathom) the hotkey drivers are responsible for doing this! I had not installed the hotkey drivers because Windows responded to most hotkeys out of the box. But sure enough, after installing the manufacturer's hotkey driver, the headphone problem was resolved.
This might work for other Clevo laptops too. So if Google has sent you to this page, I hope it helps.