The opamp would still be a good idea no? That RC filter output will be very susceptible to noise and we wish the OCXO tune input to be as stable as possible. Wh

The opamp would still be a good idea no? That RC filter output will be very susceptible to noise and we wish the OCXO tune input to be as stable as possible. When I built one of these a friend had me route the opamp output as a guard ring around the entire DAC to VCXO tune net.