In one embodiment, a power source for providing high-voltage radio-frequency (RF) energy to an instrument such as a mass spectrometer includes an RF power amplifier having an output, an oscillating RF signal generator configured to provide first and second RF signals respectively oscillating at first and second frequencies to the RF power amplifier, and a step-up circuit for magnifying the RF power amplifier output. The step-up circuit includes an LC resonator network tuned to the first and second frequencies, and an output for providing the magnified voltage to a rod assembly of the mass spectrometer.