a transformer! seriously, you'll fry(smell burnt toast) each one of those devices throwing 48volts at them, voltage doesn't work that way.
you need an 18 volt tap that will have enough amps for each 18volt device, AND a 9volt tap with the needed amount of amps for it. so you'll need to research your current draw as well.
"Tone is in the instruments. Technique in the hands. Do what you will." ~quote from some guy at the TGP forum
"Without a doubt, the quality of your instrument will effect your tone, and any pickups, effects, amps, and microphones used along the way will also have an impact on the sound waves."~Cameron Mizell