hopefully final video update. The filter is for half mclk frequency of 12.288 ( 6.144mhz ) 

some interesting notes on buffer filtering for ADC here..

https://www.ti.com/lit/an/sboa114/sboa114.pdf?ts=1625582064839

I was looking at frequency ranges just above audio but the filters job is to cutoff anything from 6mhz and higher ! 

update simulation using opa1637 as the preamp buffer to ADC.

better results in simulation at least.

Why I can't use the OPA1632 to attenuate the PG2500 with +/-5v power rails

OPA1602 attenuation and low 6mhz low pass filter