Q:

Get an electric guitar sound without an amp?

I was wondering if it is possible to get an electric guitar (used with, say an overdrive pedal) sound with an acoustic-type guitar without the use of an amp.
Similar to how resonator guitars sound very different to standard acoustic guitars, is it possible to make an electric-sounding guitar (or, more to the point, does one already exist)?

A:

Distortion and overdrive is done by clipping the signal. So there really isn't a way to recreate this exact sound without some kind of electronic device altering the sound. This article shows some simple wave forms and what distortion looks like.
http://www.howtogeek.com/64096/htg-explains-how-do-guitar-distortion-and-overdrive-work/
Resonator guitars still sound very similar to regular acoustic guitars. The way they resonate is a little different which changes the sound slightly, but not nearly enough to be confused with an over driven guitar.
Banjos essentially have a snare drum as the body and having snare wires would add a bit of a 'raspy' and 'buzzy' sound, but still not the same as clipping the actual guitar signal.
About the closest thing I could think of to actually distort the guitar's signal naturally would be to set the action so low on the guitar that the strings 'buzz' against the frets...but again, this sounds nothing like a overdriven electric guitar and just sounds horrible! lol
What goal are you trying to achieve? Is there a reason why you either don't want to or can't use an amp? If this is for a campfire/outdoor setting where you don't have access to electricity, there are small battery powered amps. However, I've never used one or heard one so I can't speak to their quality (I would imagine they're not great).

A:

You can approximate electric guitar sustain by playing a fiddle bow on the unwound strings.  You need to apply resin to the fiddle bow to get it to sound and you need to clean the resin off of your guitar after you play or it may affect the finish.
You can also approximate some electric guitar like sounds by playing with a slide or bottleneck on the unwound strings.
You can approximate an electric guitar crunchy overdrive tone by playing power chords while strumming the lower-pitched strings so hard that they bounce off the frets and produce fret buzz.  The other strings have to be muted for this to work.
For example this A5 power chord:
%5/1.7/3.7/4.X/0.X/0.X/0

or this D5 power chord:
%X/0.5/1.7/3.7/4.X/0.X/0

If you're playing into a PA, you can get electric guitar-like feedback and sustain by getting close to the monitors or facing into the main speakers until your guitar signal starts to feed back.  The trick with this is muting all of your open strings and partially muting the strings you play so that the feedback doesn't get out of control.

