Most effects run off 9 volts, but a lot of them can run off 18. The Fulltone OCD, Earthquaker Devices Monarch, and the MI Audio Crunch Box are just a few examples. If you don’t have an 18 volt power supply and want to get some different sounds and more headroom out of an effect, try this charge pump daughter board. It won’t get you all the way to exactly 18v, but should get you pretty close. You could build it into a 1590a to have an (almost) 18 volt power supply, or build it into a pedal with a switch to toggle between 9v and 18v supply.
Note: Always check with the manufacturer if your pedal will run off 18 volts before you use this circuit. I am not responsible for any blue smoke, fire, cursing, and/or broken effects that may result from improper use of this layout. 😀