Who wants an oscilloscope?

[Grumble]

Everybody in the DIY world sometimes need an oscilloscope, and since we are mostly working in the audio range there is an easy, cheap solution.
An oscilloscope is nothing more than a analog to digital converter and a way to show the signals. Well, the good news is that every body (almost everybody ) has this stuff at hand.
What you need is a sound card and a pc (laptop) and an attenuator.
There is one downside to using the sound card and pc as a scope: You can't measure a DC voltage, low frequency (~20Hz) at best, so there you still need your multimeter.
The attenuator is necessary to prevent the signal from getting distorted or even the input of the sound card destroyed by the higher voltages used in a (module) synth.
There are a lot of free programs/diy sites that offer a scope program and building instructions for building an attenuator.
Some programs not just show the signals, but also make it possible to show a power spectrum (great for checking out filters! and noise sources)

Ok, here are some sites:

http://makezine.com/projects/sound-card-oscilloscope/
http://www.instructables.com/id/Use-Your-Laptop-as-Oscilloscope/step2/Electronic-scheme/
http://homediyelectronics.com/projects/howtomakeafreesoundcardpcoscilloscope/

[umschmitt]

… and a GNU/Linux version!
http://xoscope.sourceforge.net/
(gotta love the component placement in the hardware section)

[Grumble]

Nice, but...:
They write that the scope goes from 10 nS to 2Sec per division.
And I think that the 10 nS is a typo