Using high (treble) and low (bass) frequency beat detection to control stage lamps can produce automatic light jockey for disco or any music performance. Instead of using general level of music signal to control a disco lamp, the circuit presented here uses two separate channel to give more complex variation of light flashing pattern. The dynamics of music signal is characterized by prominent beats in the high and low frequency range, mostly composed of cymbal and bass drum attack that lead the music beats.
The circuit of each channel is composed by a common emitter transistor drive, which is controlled by filtered music signal at its base. The signal at treble channel is filtered by R1C1, while at the bass channel is filtered by C2R2. If high voltage lamps are needed, the L2 and aL2 lamps can be replace by 12V relays, but the music level should be adjusted to give frequent switching of the relays. It is a good idea to provide a special amplifier with its own tone control or equalizer to adjust the signaling level of this lamp controller.
The circuit in action can be watched at our Youtube video channel below: