Audio jack/speakers will detect sound, but won't play it.

So, today I was trying to fix some FPS lag issues I was having in games.
I took my GPU (GTX 970) out and put it back in again, and then I downloaded the newest drivers from the Nvidia site and installed them. Happy days, right?
Wrong. For some reason, since restarting my PC for the GPU drivers to take effect my speakers had stopped outputting audio.

I uninstalled the Nvidia HD audio drivers and restarted. Still no sound.
Uninstalled all audio drivers and restarted. All of the peripherals I have (Webcam mic, USB headset and speakers had default drivers installed). Still no sound.
I installed the audio drivers my mobo (Gigabye h87-hd3) manufacturer recommended on their website. Restarted. Still no sound.

I have run out of ideas.
My device manager shows no conflicts. All drivers are up-to-date. The speakers show that they are receiving audio signals in the 'Playback Devices menu', but the audio signals just aren't playing.

The speakers work, if I plug the jack into my phone the audio will play fine, so there is no issue there.

If I plug earphones into the rear jack, no sound plays, but the audio signal is still present in the Playback Devices menu. If I plug the speakers or earphones into the front jack, the same issue occurs.

Edit: USB (headset) and HDMI (monitor) audio still works fine.
I doubt I've shorted any jacks, because they're still detecting hardware and audio, also neither front nor back jacks seem to be working, but they detect hardware and audio signals.
This is Windows 10 64-bit.
Currently have High Definition Audio Drivers installed for the speakers. Did have Realtek High Definition Audio drivers, but they didn't work either, so I disconnected it.