Abstract: The invention is directed to a transformer having notch gaps extending partially across the flux path of the transformer core and having a total gap volume which stores sufficient magnetic energy to substantially eliminate inductive voltage spikes in a clipped sinusoidal waveform applied to the primary of the transformer. As used in a low voltage lighting system in which the intensity of a filament lamp is regulated by a dimmer control which selectively clips the voltage applied to the transformer primary winding by an ac source, the invention substantially eliminates filament ringing.