Power Supply For Jaycar?

I built a Jaycar Theremin kit about 4 years ago and haven't picked it up in years. Anyway, I want to start using it again but seem to have misplaced both the manual and the power supply...can anyone tell me what the output voltage and polarity is of the required transformer/wallwart?

9 to 12 V DC, the inner contact is (+) and the outer (-)

How does power work for the MK2? 
I built it and found a 12VAC supply I had, however, it doesnt work when both contacts is the AC input, so do I connect the 2 wires together to the center one (which seems risky) or what? 

Sorted it with some cleaning and covering all solder holes (where there was several options), but mostly with understanding that DOWN equaled ON :D