Can Anyone help with a schematic of a PC Osciloscope which does not directly use the sound card?? It can use the soundcard through a Op-amp or buffer so that the card won't blow up if something goes wrong... I hope it to have a DC and AC testing capability of around 50v.. A serial or parallel port option other than sound card input would also do fine..

 

There are other ways, but they cost $$$. The sound card is a built in ADC, though limited. I did a search out there a while back, there is everything from USB to printer port, but they are not free (cheaper than an oscilloscope, but everything is relative).

If you feel real adventerous I've got a design I've been meaning to finish forever...

http://forum.allaboutcircuits.com/showthread.php?t=12149

 

Here's another one:
http://xoscope.sourceforge.net/hardware/hardware.html
I haven't analyzed the circuit, but I'd use a TL072 instead of the TL082; less noise.

 

I've tried thinking abt the above ckt sgtwookie, but its says its for Linux and formats are in the same..