BabyGeezer:
i have a 12V DC adaptor, can i then use a 7809 and a 7805 to drop the voltage over two 'regulators' - ie. dropping from 12V to 9V and then subsequently to 5V.
You could put 2 7805's parallel, guess you still need a heatsink, though a fairsize piece of Alu would do the trick the 7805's will tell you if it's okay, they have automatic shut down for over-current and over-heat.