Some questions regarding input stage of audio signals to the pre-amplifier
Resistors to right of Cap are in parallel.
Resistor(s) to left of Cap are in parallel.
Effective Reff is Rleft + Rright.

Radian Freq of RC LPF is 1/Reff*C.

Hertzian Frequency is 1/(2*piReffC) 







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