Quoted from a post by KEITHM from the MUSICRADAR.com website
in response to a queery about which Boss pedals take 9 and which take 12 volt power supplies:

"Older pedals, back in the day, assumed (rightly at the time) that power supplies were not regulated, so to ensure 9v available at the PCB, they told you to use the Boss ACA (12v) power supply. Then in the pedal they use a resistor to drop this to closer to 9v. if you use a 9v supply (such as the modern boss PSA 9v adapter which is what you'll get if you walk in to to a shop and say "Boss pedal power supply please") on one of those old pedals (that say on the base, 'use an ACA supply.) is a crapping-out sound - as the 9v is being dropped further. On the other hand if you then daisychain the ACA-requiring pedal with a modern PSA-requiring Boss (or other normal 9v pedal) then the shared ground sorts things out and all is well."

I just wanted to add on and say that I bought a HOSA power supply extender and have great results with it, with the exception
of one gig when it failed to power my large BOSS OD20 Distortion box (any ideas why that is, oh knowledgeable ones?)

That's another way to save bread.

I have a Power-All daisy-chain power supply, made by Godlyke. It comes with cords for different kinds of pedals. I just use the 5 daisychain with standard pedals, and I'm having good luck with it.

americanmusical.com has them for $35. That's damn cheap for a power supply that runs multiple pedals.