[sdiy] very cheap oscilloscope & signal generator?

[db]

I'm looking for a *very* cheap oscilloscope that would be used only for 
audio signal tracing.
I envision a probe with a USB jack at the other end, and software to do it all.
Does anyone make a very cheap PC based scope that's usable?

Also, I was using my mp3 player as a signal source, and it got some dc on 
the output, and fried it.
Now I'm looking for a very cheap signal injector too. Is there something 
like a 555 circuit with some output protection in it, that is very cheap to 
make or buy?

I need these for just a few hours every few years, so cheap is the key.





dennis.barton:skylab2000[socal]