Here is the part of deemphasis circuit of a famous radio. Built around NE5534 output buffer. 33.2K and a choice of a capacitor supposed to form either 50uS (EU) or 75 us(US) time constant deemphasis correction. Currently in the circuit resides 2.2nF combined value of the capacitors and indeed with 33.2kOhm the calculated time constant is around 75uf . The thing is I have no idea how this supposed to work in a feedback loop of an Op-amp . Can somebody sim that circuit? Radio is rolling off the upper frequency like a mofo. By the time we reach 15Khz the amplitude of the signal is at 30% of what the level at 1Khz is. This using FM generator and audio analyzer.