Query on crackpot scheme for recording audio with extended bandwidth

[KiM3Ce]

Thanks! I'm thinking a modern data acquisition system might not be prohibitively expensive.

https://www.ni.com/en/shop/data-acquisition.html

Ideally I would like to do the digital signal processing like the Accuphase tuners do, without buying a $9,500 tuner :-).

https://www.accuphase.com/tuner.html