A simple and easy USB soundcard hack for an Oscilloscope.
But please be careful, no protection is build in. Input signals up to 5V should be save.

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Download xoscope-2.2.tar.gz from:
https://sourceforge.net/projects/xoscope/

 $ tar -xvf xoscope-2.2.tar.gz
 $ cd xoscope-2.2cd

one has to fix the package (at least for Arch Linux), remove the line 37 from display.c. Open:

 $ nano display.c

and remove:

 void    *font;

Install the package:

 $ ./configure
 $ make
 $ sudo make install

Download micoscope-linux-1.0.tar.gz from:
https://sourceforge.net/projects/micoscope/
Unpack it and run it:

 $ tar -xvf micoscope-linux-1.0.tar.gz
 $ cd micoscope-linux-1.0/MicOscope/
 $ ./MicOscope

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Use a cheap USB soundcard. Open the housing and solder a wire to the ground and the signal pin.

Close the housing, that's it.
A decoupling capacitor and a potentiometer to attenuate the signal would be useful, too.

             Poti
 Signal ____| | |______GND
              |
              |____100nF_____Mic Input

If you want build a protection circuit here is a simple one:
[[http://xoscope.sourceforge.net/hardware/hardware.html
One can use a 1N4148 diode instead of 1N914 diode.

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