Thanks, I'll give that a try, think I have a few lying around (adapters , not cats!)Looks like the input jack goes through a ferrite bead, a Panasonic FK series capacitor, then a MIC39100 linear regulator (3.3V).
Since the lowest voltage rating on the capacitor series is 6.3V and the regulator is dropping things to 3.3V, my best guess is you want something like a 5Vdc center positive input.
Again, best guess, for which I accept little to no responsibility. May set your cat on fire, etc.