I'm simulating the circuit below in LTspice and there's something I don't get regarding C3 and C4. Suppose the input signal is a 32 uArms 60Hz current as shown. This value multiplied by the burden resistor gives (32uA * 1.91k) = 61.12 mVrms. However, in the simulation if I measure the voltage at the burden resistor, I get about 30mVrms signal. What is the effect of C3 and C4 that is causing the input signal to be reduced?