Q) I have an old Boss ACA style pedal that requires 12V DC, yet you say that your Powerstation (which is 9V DC) can power it?

A) Yep - just so long as you're powering at least one other normal 9V pedal in the chain, then it'll work just fine.

The old Boss ACA pedals use 9V batteries don't they? The DC input jacks on the back are hooked up to a current limiting resistor to drop the internal voltage from 12V to 9V. Hooking up a 12V ACA pedal with one or more other 9V pedals bypasses this resistor so that it will work just fine with a highly regulated 9V supply like the Diago Powerstation.

So why design pedals to run from 9V batteries or a 12V power supply? For those who are interested..........

At the time when Boss first started making pedals, unregulated power supplies were the norm. With an unregulated power supply; as the current load is increased (in this case as you try to power more and more pedals) the voltage drops. If the voltage drops your pedals can either sound crap or there may not even be enough voltage for it to work at all. So Boss designed their unregulated pedal power supply to be 12V DC, and put a current limiting resistor in the DC input of every pedal, so that different loading wouldn't have so much of an effect on the 9V needed to power the pedal. Now that we have access to well regulated supplies, it's not an issue any more.