alt Hacker NewsVinyl is far from open source CD due to limitations of phisical format and the fact that good vinyl contains specifically mastered for vinyl with those limitations taken into account.
You can still easily buy Bluray player and open source your discs with ARM (not CPU/SoCs, different one)
If you're referring to the RIAA equalization curve[1] that is completely open and well defined.
[1] https://en.wikipedia.org/wiki/RIAA_equalization