How to get audio input from speaker

I was wondering how I would go about for my arduino uno to receive audio input from the female jack from my bluetooth speaker (Jambox Jawbone). I want to eventually process this audio using FFT for an LED strip project - so any guidance hardware related would be really helpful.

You need to bias the input in order to read the negative half of the AC audio waveform. There is a schematic at the bottom of [u]this post[/u].

Then of course you'll need a [u]Y-Splitter[/u] and an extra plug/cable, etc.

DVDdoug:
You need to bias the input in order to read the negative half of the AC audio waveform. There is a schematic at the bottom of [u]this post[/u].

Then of course you’ll need a [u]Y-Splitter[/u] and an extra plug/cable, etc.

Thank you for the reply, Doug. I’m not sure what the voltage peaks are for the audio signals from my iphone 6 plus - I found one source that said commercial line out specifications are 2.2v peak to peak, but I’m not sure if that is true for my iphone. Also, wouldn’t it be ideal for it to output 5v peak to peak therefore an op-amp is needed?

  • I found one source that said commercial line out specifications are 2.2v peak to peak, but I'm not sure if that is true for my iphone.

A quick Google search says the iPhone (I don't know which model) puts out 1.1V RMS which is about 3V peak-to-peak. (That would be the maximum with a loud song/program at maximum volume.)

You can try it to see what kind of readings you get. You can run the Analog Read Serial Example (take-out the delay) or if you copy the code from the link I gave you, there is a few lines of "commented out" code to print-out the peak and average levels on serial monitor. And although that code is a LOT simpler than FFT it does have automatic sensitivity adjustment and you can copy that concept for your FFT effect.

Also, wouldn't it be ideal for it to output 5v peak to peak therefore an op-amp is needed?

If you amplify too much you'll clip (distort) so it's best to leave some headroom. Distortion adds harmonics and that will foul-up your FFT. If you add an amplifier you'll probably need a volume/sensitivity control. And, use a "rail-to-rail" op-amp if the op-amp is powered from 5V.