This is the rare, legendary Raven Labs PHA-1 all-battery preamp designed and built by Steve Rabe, founder of SWR. It has a remarkably clean, clear tone and can be used as a full-fledged preamp or practice amp with headphones, no power cord required. This unit runs off 2 9v batteries only.
I am the original owner of this preamp, which is S/N 0048 (really!) and is in overall good shape. A few years ago I cleaned some slight oxidation from the battery contacts, but it has not returned and did not impact the performance of the preamp whatsoever, then or now. I'm including a 1/8" headphone adapter with the preamp. $210 shipped CONUS