Up for sale is a Grado RA-1 battery powered headphone amp. I have tested this with a pair of AKG K20 headphones and it works perfect and sounds great! Uses 2ea 9v batteries, not included. Some light scratches/dings as you can see from the pictures.
This was left over stock from Audio Den, a dealer in Van Nuys, California, and has never been sold. I can provide a receipt on request, but I do not know if Grado will provide a warranty.