the amount of turns on the primary side of the transformer determines the output voltage (in this case). by turns i mean the amount of turns of wire around the transformers core. that's right, if you hook a capacitor up to the high voltage output, it will store the charge, and since you said you want a shock box, when you press the switch, the current will flow through the transformer, and come out at a higher voltage, then you can store it in the capacitor, then you don't have to press the button everytime you want it to shock, just touch the capacitors leads, the more presses of the button, the higher the voltage in the capacitor will have (to a point) and you can change the "shock power"