PeteTry changing your input stage to the configuration depicted in the attachment. The input amplifier can then be something like an OP27 without affecting performance. The noise spectrum at the first opamp output will actually be reduced to the opamp (and series resistor) input noise at frequencies outside the tuned circuit bandpass rather than being significantly enhanced as in you circuit. The first opamp will ouput also be dc stable with a zero signal output of around zero volts unlike your circuit.
This will do nothing for the rather large phase shift tempco, but at least its a more rational design.
In fact your circuit performance should improve if you just delete the first tuned circuit.
You still need to think about a suitable limiter that doesn't switch the power supply noise to the output during stauration.
Bruce
ModifiedRawsonZCDInputStage.pdf
Description: Adobe PDF document
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