[wots]

i am looking for a full-sized battery powered headphone amplifier. any suggestions?

 

[Uncle Erik]

Why?

Batteries are inferior in lots of ways. Primarily, having to replace the battery. They're expensive and you don't want to get suckered into replacing some proprietary battery for hundreds of dollars every few years.

If you really want to do this, you can DIY a battery pack for any amp. A few car batteries and some other parts will power one.

Though I'm not sure why you'd want to. A well-filtered transformer isn't any different from a battery, except it costs less and you don't have to replace it. There's no advantage in cost or performance to having a battery.

 

[DaBomb77766]

...O2 comes to mind?  Pretty sure it uses rechargeable 9V batteries.  It's pretty much DIY-only right now though.

 

[Parall3l]

 
 
 
This picture comes to mind 

 
Theres some Headroom amps that might meet your requirements 

http://www.headphone.com/headphone-amps/headroom-portable-desktop-amp.php

 

[fusionramjet]

I think Red Wine Audio's Amps are battery powered.