Guitar Effects Canada - Fulltone FPS-3 18 Volt Power Supply
Many effects are capable of running at 18 volts... the Fulltone OCD, FD2, FD3, PlimSoul, GT500, Secret Freq, and Bassdrive, to name a few. At 18 Volts pedals completely change their behavior and have a lot more headroom, and it can sometimes make a pedal you didn't care for become one you love. Don't buy ANY power supply unless it is "regulated." It will hum, will not stay at the intended voltage and you'll end up calling the pedal maker complaining to him for something that he has no control over.
There used to be a couple of good, QUIET 18 volt adapters available, but now everyone has gone to the horrendous "switching" power supplies, which put out some very strange and annoying noises at various frequencies... some even sounding somewhat like a broken Theremin. I designed, manufacture and sell the only Noise-Free Class 2 Regulated 200 milliamp adapter. These are only for use with US-style 120 volt electricity.