allanhurst:
1/ You don't really need opamps - it just takes the guesswork out of finding r3,4 values.
2/ A LM358 won't quite do - you need a rail-rail opamp.
3/ If you intend to use high current displays, opamps would be a good idea - but be sure they've got enough drive capability.LED display - the worst case is displaying '88', with 14 segments on. Allowing 5mA each that's 90mA - more than most opamps can handle..
But, of course, you could drive them directly from the supply with suitable drivers.....
I'll have a ponder...
Allan.
Ok, I'll give it a shot without the opamps 1st. The diodes I have are rectifier diodes, so I'm ordering some 1N4733a diodes. I figure I'll add some opamps to the order, just to have them on hand if I need them. If the LM358 doesn't work, can you suggest one that would?
As you can tell, I'm a bit over my head when it comes to power supplies ... but learning.
allanhurst:
Just saw your post , crossroads - neat little displays. But this is next next to his pedal - 4-6 feet away? so perhaps too small - and of course the reading angle is limited.
Exactly. The device will be on my pedal board, on the floor, while I am standing. Typically in a poorly lit environment as well. And to boot, I am color blind 
(my 10 year old daughter has to help me with resistor identification LOL) This is why I was looking for a 2 digit, standard size, 7-segment display. But a small LCD would work too, if I can find one that fits.
BTW: Can I just say the "one post per 5 minute" rule on this forum is extremely annoying....?