Abstract: A display apparatus is provided which is responsive to an audio signal to vary the illumination of a light source. The light source has a variable resistance having an initial value when the light source is cold and a larger value when the light source is warm. The display apparatus includes a circuit having a pulse generator which periodically passes pulses of current through the light source to warm the light source prior to illumination of the light source by the modulator sufficient to substantially increase the response time of the light source upon receipt of the audio signal.