Realtek PC support has confirmed that the crackling issue is caused by the
SiS 671DX+968. chipset present in my laptop. According to them, their drivers are generic, but they cannot guarantee that they work on all systems. Still, they have suggested that I should download a newer beta release (5898), which unfortunately will take a lot of time at 4 KB/s

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I'll report my results as soon as I have them installed in my system.