Scaling music-driven LED box?
Note, the original solution is a horrible way to get music reactive lights.

But I will still answer it.

Use a small transistor with better gain, to drive the low gain but high current TIP31. Allows a smaller current from the audio, but requires a higher voltage.







simulate this circuit &ndash; Schematic created using CircuitLab

Might not work, if the audio signal can't provide a 0.65 + 1.8v drop across the small transistor vbe and tip31 vbe. Still has a risk of blowing the speaker driver, but less than the original. I hope you don't care about your ipod or computer output too much.

Only provides a single channel. If you use one on both Right and Left audio, you can get two colors.

Better Way

Use an opamp to boost and split the audio:


Use one output to go to the speakers, and use the other two for your led driving transistor. Duplicate for both left and right audio. Leave out the 50 uf capacitor for the led outputs.