I need to step down 12vac to 9vac. The details. I am making colloidal silver. I have a 12vac 2amp timer that switches polarity between the two silver rods every 2 mins. 12v to the silver rods is a bit much. 9v would make a better product. So what is the simple way to do this, and still allow for the polarity to switch? I know how to solder, and can tell a hot wire from a ground. That's about as far as my electrical knowledge goes, so please keep it simple for me. Sorry for my ignorance on this subject. Thanks in advance for any advice.