I can find the for your specific model's driver package.
Do not download random driver files from untrusted third-party websites. Instead, download the official Apple Boot Camp support software directly. apple macbook pro a1278 audio driver windows 10 high quality
Pros and cons
Install Windows 10 on your Mac with Boot Camp Assistant - Apple Support I can find the for your specific model's driver package
Websites claiming to have "HD Windows 10 drivers" for the A1278 are usually hosting malware or generic packages that will not fix the optical jack issue. Stick strictly to archived Apple Boot Camp files. apple macbook pro a1278 audio driver windows 10 high quality
: This is the recommended package for older 64-bit Mac hardware and is compatible with Windows 10.