You can disable the audio from your BIOS configuration; however, this means that that there will be no audio from the audio jack, HDMI or the mini-DP.
I have tested the behavior you mentioned, but the issue did no happen. I played a YouTube video, then plugged an iPhone earphones and they sounded just fine.
Try the following;
- Enter your BIOS setting, and press F9 to load defaults.
- Install the latest Audio driver, see here for it; Download Realtek ALC* Audio Driver for Intel® NUC Kits.
- Make sure that in your Playback Devices you select your headphones.
Problem Solved: Adding a dummy audio device HELPS!
My monitor is not equipped with speakers. So adding a dummy audio device forces the Windows audio subsystems to work.
After installing a dummy audio device(Device Manager -> Adding outdated devices -> Pick some audio driver, e.g. Intel WiDi Audio ), there's always an audio device and audio output can be automatically redirected to earphone output.
Conclusion: The audio driver is not well-designed.
Verifying the discussion, if you want to disable NUC's front-panel audio jack the best option for you is to access to the BIOS settings and disable Audio.This BIOS has the option to disable the Audio(Front panel) or the HDMI/ Displayport per separate. If you uncheck the option Audio, This will disable the front panel audio only.
Try the following:
1. Enter the BIOS settings
2. Click in Advanced >Devices >Onboard Devices
3. Uncheck Audio
4. Make sure the HDMI / DisplayPort Audio is option is check
5. Save changes (F10).
The best option is to have the NUC updated with the latest drivers and BIOS
> BIOS Update [SYSKLi35.86A] / Version: 0063 (Latest):
> Realtek* High Definition Audio Driver for Intel® NUC Kits
Please let me know how it goes.