There are many ways to make a set of lamps blink, keeping pace with the music of an amplifier. You can use triacs, SCRs, transistors, etc. The solution given by the author of this project is one of the simplest and it is nonetheless interesting and efficient. In the project shown in the figure, the author uses a 6 V relay, the type used in the Volkswagen car horn. The energy from the amplifier output (which must have enough power to energize the relay) causes the relay to turn on at the peak of sound, activating the lamps. The 5k wire potentiometer is used to adjust the operating point of the circuit, according to the level of the music. The lamps suggested by the reader must be colored from 5 to 40 W, and the current limitation of the relay contacts must be respected. The author of the project informs that the relay also "accompanies" the music, emitting in its rhythm a noise similar to that of a cicada. We note that other types of relays sensitive to 6, 9 or 12 V can be. experienced, if the impedance of your coil is not too low to the point of charging the amplifier.
