[sdiy] Let's talk AC, DC, electrocution, death, misery, and grounding.

[Dave Manley]

Horton wrote:
> 2. How could you get electrocuted by plugging in something that's only
> spitting out an output, anyway? I mean, if I make a piezo mic, it's
> only going to be outputting a signal, not taking any voltage into it.
> Shouldn't I be able to plug that thing into anything from a tiny
> battery-powered amp to a marshall stack without worrying?
The answer is you shouldn't, but that doesn't mean that you can't.

When you plug into an AC outlet, only one side (for a 120VAC), is "hot", 
the other side is neutral.  If the plug is wired incorrectly, or you use 
a mis-wired repaired extension cord, or someone has defeated the plug's 
polarization (one prong is normally bigger than the other), or you live 
in an old house with unpolarized plugs, or you cut the third prong from 
a three prong plug, etc...and if the neutral is connected inside your 
amp (or other electronic product) to the metal chassis, and that chassis 
is improperly connected to the sleeve of an input jack, and you touch 
the sleeve, then you will be touching not the neutral, but the hot, and 
you could get shocked.

So there's a scenario.  With modern wiring and equipment you shouldn't 
get shocked.  That doesn't mean it is impossible.

In old equipment neutral was sometimes connected to the chassis - for 
reference:

http://en.wikipedia.org/wiki/AC/DC_(electricity)
http://www.eham.net/forums/Misc/8758
http://www.epanorama.net/documents/groundloop/problem_solving.html

Some misc electrocution stories:

http://www.cbsnews.com/stories/2005/10/31/national/main995829.shtml?source=search_story
http://www.gearwire.com/forum-guitar-electrocution.html

Good luck! X-)

-Dave