I would like to connect a signal coming from a line receiver to several op-amp based filters in parallel. The basic topology (high-shelf) looks like this:
What I don't understand is the meaning of R1. Why does the positive input have to be shunted to ground? Doesn't it act as a voltage divider since the inputs of the op-amp have their specific input impedance?
My question is, if I want to connect several of those in parallel from one output, do I need both R1 and R4, or is one time enough? Do I need them at all?