Why my Ibanez AD80 can be powered by 12V?

As we know,the ad80 is a 18v powered unit.
While I power it with a 12v output from my Voodoo pedal power 2,it works and achieve longer delay time than with 18v.
No effect when I plug the 9v power.

The 18v probably just gives it more headroom (cleaner repeats). Not really sure from a technical standpoint though!