I couldn't find any mentions of what audio codec it uses in an initial search, but I see "HD Audio" and other sources online say it's a Realtek, so this seems to be a standard Intel HD Audio codec. What's lesser-known is that most if not all of them have a built-in EQ function which can be used to accomplish this (and perhaps the original vendor's Windows drivers already do), but it's not well-documented. Linux has some code for that too (search for EQ in here):
https://raw.githubusercontent.com/torvalds/linux/master/soun...
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