What do the two "33k-100k" resistors do in this PPIMV ?
Its hard to say because post master volume is an il-conceived design anyway. Anyone whom endorses such a design should be held in immediate suspicion of incompetence.
However, for a scratch build, my approach was to have the output of the PI drive a low impedance buffer, then a post PI Master Volume. This reduces the value of the master volume pots from 1 Meg, to 100K, and no issues with parasitics.