Roland TR-808 Bass Drum Breadboard Project

In modular synths the power supply will be fixed to the case and shared between all the modules via a distribution bus. There's no point making a seperate power supply for each module.
The 808 is MAINS powered and has an internal (center-tapped) transformer which converts this down to some useful voltages.
I strongly advise against using a VCT transformer as this is potentially LETHAL! (You could die if you make an error!!!)
Stick with the Adafruit split supply as this takes care of all the deadly bits for you..
When you build enough modules to exceed the 500mA per rail provided by the Adafruit PSU you can either buy another Adafruit supply and keep doing that or buy a nice modular synth case/psu like the Doepfer LC9 or a microZeus by tiptop audio http://www.tiptopaudio.com/zeusmicro.php.
There are a lot of cases to choose from that are factory made but obviously they cost a lot more than building your own.
I built mine for under £20 and it can provide 750mA on each rail (+12V rail and -12V rail)