Adding 9V regulator after 12V reg OR just use adjustable reg?

[disorder]

I'm building a bench top power supply for testing circuits. I was gifted an old +/-12V power supply. Its a simple fused-AC in to a toroid transformer and bridge feeding LM7812A and LM7912A regulators with necessary filtering. I'd like to keep the ability to use the +/-12V for testing preamps and such, but I'd also like to use this power supply to get my main 9V supply for usual guitar pedal designs. I'm wondering what the trade-offs are between the two ways of achieving this are.

1 - Simply feed the +12V reg output into a +9V regulator?

2 - Switch out the LM7812/LM7912 for three terminal equivalent adjustable regulators and have each rail adjustable?

[GibsonGM]

For ease of use, I'd just make a "box".  Call it is distribution box if you want.  Use banana jacks and the like to feed it and to send it out to your breadboard, etc.

Put in a LM317, feed it +12V and dial in your 9V.   Or 5V, if you want, for logic-type circuits!   You could put the necessary components on a switch to do 9 or 5, or just use your meter to dial it in when you use it.

That's how I'd do it, no messing with the nice +/- 12V you have.  Any errors or whatever will then show up offboard rather than in the nice supply.

[davent]

I'll second what Mike said, an external box for the second regulator. Built a 12v/9v with fixed regulator to put to use a small  transformer i had.



dave