A differential pin to RF adaptor includes a center conductor contact with an RF connector on one end and a signal contact on the other end. An insulating sleeve surrounds the central contact. A reference contact surrounds the insulating sleeve. The signal pin of the differential pair interfaces with the center conductor contact of the RF connector. The adaptor is structured to slide down over a pair of pins/leads so that the reference contact abuts a circuit board attached to the pins. The pins/leads are shielded all the way to the circuit board, which shields/isolates the pins from common mode and other types of interference. The adaptor maintains the shape of the signal pin and the reference pin during testing. The adaptor maintains a fixed impedance of the pins, which reduces or eliminates uncontrolled impedance and hence preserves system frequency response and reduces/eliminates erroneous ripple currents.