AW: "Stacked" Power Supplies - any thoughts?

[Haible Juergen]

Hi Gene,

sorry for the delay, just came back from hollidays.

	>My question is about regulation stability - can this be an issue?
Each
	>one of these supplies is a dual 723/pass transistor design. I know
that
	>a single 723 has pretty good stability as far as maintaining a
constant
	>output voltage regulation under varying current conditions, but how
	>about regulated-regulation, or even regulated-regulated-regulation?
Will
	>stacking these supplies cause any cumulative noise on the power
rails,
	>or any other effect?

I would be careful. I bet you will run into some side effects none of us has
thought
of before. Stability of coupled systems is a tricky thing. It might work,
but I would
not rely on it. Besides, you waste a lot of energy because you have three
times the
voltage drop over 6 regulators than over 2.

This is what I would do instead, If I got these 5V PSU's for cheap: I would
modify
one to get a +/- 15V output, changing a few resistors (yes, for the 723 it
involves
a change of configuration, too), and exchange the capacitors to higher
voltage
types. Then you need a new transformer, of course. Good chance to go for
a torioidal, if there wasn't one before.

Ok, I don't know if it is practical in your case. The capacitors might be
larger,
and might not fit in anymore. But I'd ckeck this option, at least.

If you choose the right xformer voltage, you can get almost the same current

from one pair of regulators as with 3 pairs of 5V regulators.


JH.