I was having the same audio issues as the OP, but everything I tried did not resolve the problem. I couldn't come up with a solution, so I decided to install Windows 10 on my other SSD.
After installing windows 10 I was having a similar audio issue. I tried installing the 1150 drivers from the gigabyte website and that did not do the trick. After several attempts I wondered if the BIOS was hanging up my success.
I updated my motherboard (Z170X-UD5 TH) to the latest firmware. After the update the sound on Windows 10 worked immediately.
I clean installed OS X El Capitan, on a separate SSD, following the OPs tutorial.
- I installed the 100 series audio driver through multibeast.
- then I did the step 2 of this guide :
"Download the latest version of AppleALC from the GitHub Releases page. Mount your EFI partition, and copy it to Clover/kexts/$OS_VERSION or Clover/kexts/Other." THANKS OTTOMEZZI!
This gives you all the correct audio drivers
-Reboot
- Next, use the Clover Configurator, mount the EFI, and run audio_realtekALC-110 from Toleda
-Reboot and you should have Sound!