Headphone amplified made for teams requiring monitoring on up to three headphones in parallel.

Very sturdy case, similar to Sound Devices. Locking connectors. Thing thing is made to take serious beating.
Works either from AA batteries or 5-17VDC external power (so, almost any external solution will do).

See small review at: http://www.headfonia.com/superlux-ha3d-amplifier/
User guide: http://www.superlux.com.tw/upload/function.product.info/65ccd6f5-cbc1-4b85-a0aa-3aef01daf3ab/resource/um_HA3D_web_en.pdf

Price: $159

http://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l2736&_nkw=Superlux+HA3D