A light emitting diode includes a substrate, a reflecting layer, an active layer, a transparent electrode, a first photonic crystal structure, and a second photonic crystal structure. Pedestals are deposited on the LEDs with each of the pedestals in electrical contact with one of the LEDs. An end portion of the sliding unit is slidably connected to one side of the rear load plate. The adjusting module multiplies the magnitude of each tone by the scale factor K, thus the volume of the music is kept to a suitable level without suffering from too small volume problem or signal distortion due to too large volume.