[baskerville]

So I play electric guitar, but sadly dorms probably won't allow me to crank it up. So I'm planning to use headphones, and I wonder about using headphone amps to amp an electric guitar? 
 
 

 

[ProtegeManiac]

If you mean a headphone amp here and hook it up to an electric guitar, I wouldn't try that. I'll let an EE get into the more technical bits of this, but basically there's a reason why you shouldn't just hook up an electronic instrument into just about any amp; something about the way the waves and peaks are vs mastered/recorded sound.
 
There are however some guitar amps that have headphone outputs, even the 5w practice amps. Even better, I think I've seen some on eBay that are purely headphone amps for guitars - the 1/4" plug sticks out of its side, you insert it into the guitar jack, then hook up the headphone. Make sure they fit your guitar's jack though, the ones I've seen probably won't work with guitars that have the jacks flush and angled into the body (so you can use straight plugs without them sticking out).

 

[mikeaj]

You still need a guitar amp to pick up the signal, increase the level to a suitable amount, do effects processing, etc.  Just send the (line) output of that device to a headphone amp rather than speakers; or, as mentioned above, some guitar amps will have an integrated headphone output as well.  

 

[DudeMyCans]

You may get away with it if your guitar has active tone controls. I've done it in the past with an MTD bass into a Creek OBH-11 with limited success, but you're probably better off buying a real cheap practice amp with a headphone output or something meant for the job like the Pandora guitar headphone amp.
 
The Pandora has the advantages of being small and battery powered, so you can clip it to your belt or shove it in a pocket and has all sorts of effects. You can also blend it with your iPod etc for play-a-longs. 
 

 

[spoonstar]

I haven't tried hooking my electric up to a headphone amp directly, but I'm going to further reinforce the suggestion that getting a proper guitar amp with a line out/headphone out connection is your best option.
 
Some amps keep volume of those outputs relative to the output level of the speakers, so watch out for that. My amp won't let me listen via headphones at any reasonable level unless I have the speakers cranked as well.
 
 

 

[dadeus1]

You guys are way over thinking this.  The idea behind this is to be portable, not tied to a computer or an amp.  As for effects, I am practicing and don't need any, just a simple way to plug a guitar to headphones.  Anyone do this with a cell phone?

 

[ProtegeManiac]

  The idea behind this is to be portable, not tied to a computer or an amp.  As for effects, I am practicing and don't need any, just a simple way to plug a guitar to headphones.

 
If that's the case then Fiio has a practice amp designed specifically for headphone use.

 

[Makiah S]

... back in the day I used to plug my Schecter Daimen 4 right into my Hybrid Tube Amp then into my DT 880... it sounded pretty stellar to my ears :/