Power Supply – I would like to try running my pedals at 18 volts with 2 batteries. How do I get 18 volts out of 2 batteries?
Take 2 battery clips, connect the black (negative) of one to the red (positive) of the other clip. Now use the two remaining clips as usual, when you measure the voltage with a multimeter with fresh batteries, you will measure around 18 volts. You should verify that your capacitors are rated to handle the higher voltage.