Thanks a lot! I know almost nothing about electronics, but I know how to use a soldering iron, so maybe it’s time learning something :)[/quote]
Indeed you should!
Ok, is supposed that this component will do the trick.
Is an OpAmp and it cost just 5 USD so it worth the trying. 
As it says in the comments: “You’ll need to short out caps c5/c6 as those make this circuit a differentiator. In other works, it blocks very low freq signals including DC.”
I don’t have accesso to that piece so I can’t test for you. I live in Uruguay so it will take a wile till it gets home.
Try first with some cheap sound card or mp3 player just in case, and put a couple of diodes in between to avoid any problem, like burning your audio source.
And remember to be safe, always wear protective googles in case something explodes.