Music visualizer - help in reading speaker signal

Hi, I'm trying to build up a Led Audio visualizer based on Arduino and a BT audio amplifier.

The project is composed by:

  • Bluetooth audio receiver and amplifier (KKmoon TDA7492)
  • 2 speakers
  • Arduino
  • many resistors and leds

The target is to "read" with arduino the speaker signal and light on/off a rows of led depending by the signal intensity.

For test purpose, when I use the source signal coming out from the audio out (jack 3,5mm) of the laptop or mobile it works very well.

But, when I try to use the amplified signal (that is the only signal that I'll be available in the final project) coming out from the TDA7492 direct to the speakers... it doesn't work.

How can I "transform" the amplified signal to a line signal?

You can fry the Arduino with more than 5V. If the amplifier is powered by more than 5V add an [u]over-voltage protection circuit[/u]. You can increase the resistor to between 1K and 10K, and then you might need a 2nd resistor to make a [u]voltage divider[/u] to knock-down the signal, or you can use a potentiometer. That really depends on how loud you crank the speaker.

You also need to bias the Arduino input since it can't read the negative half of the audio signal. (You should be using that with the line input too.) There is a bias schematic at the bottom of [u]this post[/u]. The capacitor will also block the higher DC bias out of the amplifier, but reverse the capacitor since the amplifier output voltage is (probably) higher.

That's a bridge amplifier so neither speaker connection is grounded. Just use one of the speaker connections and connect the amplifier ground to the Arduino.