At the moment says only "high definition audio device", no realtek device... I think windows just do not let install the realtek device, even if on control panel/software and tools there is a realtek driver installed, at least the logo of realtek is visible...
Try disabling High Def audio in Device manger, see if it uses Realtek May have to left click on speaker icon in system and select driver
I disable realtek digital output, now with asus drivers, i see realtek high definition audio, the same cracking sound, in every quality (cd-dvd or studio)
Would you like to hear the "funny" news? With Windows 7, exactly the same crackling sound, no matter which drivers i use....
This is given to me for repair. Spend a lot of time to service it, (overheating, no boot, screen hinges etc,) and now this...
BTW if I were you I'd put Windows 7 on it unless you want to deal with wifi problems and other problems related to sleep/hibernate/resume and fast startup (hybrid shutdown) Windows 10 doesn't always work well on old laptops.
If it worked fine with W7 return to it, it is became an old laptop, you wont gain very much with W10 There's no official drivers past vista ??? i had one area51 and had the same troubles, disable this and that, tried many things, it was with an ac97, but sometimes the device management thinked it was Realtek high definition audio .... maybe conflicting drivers with hdmi port or digital in the list can be long. You have surely searched with the hardware pid's and vid's ?
With windows 7 has the same problems. Of course searched with hardware id's, difficult to find though for legacy hardware. I am almost sure that it is driver issue, but a conflict with other hardware is of course not excluded. I will try with first chance the driver which ELDiabl0 shared and will report here. For the further rest, latest W10 works smooth, fast and stable, with no issues on this laptop. Would say faster then W7. Just had big maintenance, al hardware works ok and quite, with a properly installed W10, laptop can be used for a lot of years more...