I am wondering how can an audio signal be used to switch a transistor, if the voltage is too low? I am trying to switch some LEDs with the output of an amplifier, but it seems that the audio voltage is too low for the transistor to turn on.
I have the output of the amplifier going to the base of a BC549 transistor, the collector connected to the negative of the LEDs, and the emitter connected to ground. There's a 100K Ohm resistor each from the collector and emitter to base. The positive of the LEDs is connected to 5V, which the amplifier is also running off.
When I put some music through the amplifier, I have to turn the volume up to probably 90% of the amp's power for it to switch the LEDs.
So does anyone know how I can boost the voltage of the audio to the transistor?