[sdiy] LM431 vs LM7815/LM7915

[anthony]

I don't have very many 15V regs, but I do have a lot of LM431's and 
2SD880Y's and 2SD313's. I was wondering how much better a LM7815/LM7915 
supply would be than a bipolar shunt regulated LM431 supply with a floating 
ground buffered by an opamp with a pass transistor? OR since I DO have a lot 
of LM317L's & LM337L's would it be better to use those with a pass 
transistor than the shunt regulated supply. I seem to  recall that using a 
buffered ground with a single shunt regulated supply produces a supply with 
unequal absolute values of power rails.

Two power supplies that I am currently actually using with good results:

1N5247, K40D1 (replaced with a 2SD880Y), 10KOhm voltage divider and half of 
a 4136. OK balance, but innaccurate voltage.

LM7815, 7.5KOhm voltage divider and 1/4 of an LM339. This is a better 
supply, but it's only a +/-7.5V supply - which is perfect for what it is 
being used for.

Personally I think I like the idea of using the 317/337's with big 
transistors.

Of course then there are the 723's that I have. I have some in cans - I 
really like these and I can't explain why. When I got them out of the 
circuits they were it, the leads were still long enough to bend to fit a 
14-pin DIP footprint (OK -4 pins...) The ceramic Teledyne 723BL's are cool 
too though. I had these reserved for my Arp and Oberheim clones for the 
future...

I guess my final question is: wht do people like best? Or maybe what are the 
big mistakes to avoid that everybody seems to make anyway?

I do like the idea of using big power transformers in a linear supply rather 
than a light switcher because they make good ballast.