this is a bipolar power supply, meant for generating +/- DC with a [virtual] ground from a wall wart that outputs AC. 

using a wall wart that outputs AC is a MUST. do not use one that outputs DC! a transformer of suitable specs may also be used

two 9-volt batteries in series can be used to achieve the same result -- your [virtual] ground will be the positive and negative between the two batteries

i've one available, using the above board. 

two more potentially available, simply need parts.

inquire if desired!