"Stacked" Power Supplies - any thoughts?

[Stopp,Gene]

Hi DIY,

I'm building another modular synthesizer. It is a slow process, a bit at
a time. I'm incorporating a bunch of experiments that I've done over the
past couple years behind panels and in a case, including some
not-so-common modules like a Shepard Function generator, a quad VC
bandpass filter bank, a VC commutating filter (the Electronotes
"Quasi-Digital Bi-N-Tic" filter), a stereo 18-bit audio delay made from
Crystal chips,  and a custom octal MIDI-CV converter made from a 486
motherboard. There will be other more "normal" modules as well, plus an
ASM-1. The cabinet is finished - it is about 38" wide by 26" tall by 12"
deep. The panels are four large aluminum plates, with laser-printed
graphics on laminated paper glued to the panels. Patching is done with
banana jacks.

Anyway, I'm looking into my power supply options. The PC motherboard
will have its own supply. As for the analog side, I can always build one
from scratch. However, I have a box full of Power-One +5/-5 supplies
(1.5 amp each), plus a box full of Power-One +5 @ 3 amp supplies. Here's
my idea: take three of the +5/-5 supplies and stack them, like this:

          -5   Gnd   +5 --------- -5   Gnd   +5 ----------- -5   Gnd
+5

>From the left, we get -15, -10, -5, Ground, +5, +10, and +15 volts.
Notice that the center terminals (the "grounds") of the outer two
supplies are used for the -10 and +10 rails. The two outer supplies will
have floating chassis, the center one an earthed chassis. The primaries
of all three mains transformers would be connected in parallel and
driven by 110 VAC.

Since each supply output is rated at 1.5 amps, then I am assuming that I
can provide 1.5 amps at -15v and 1.5 amps at +15v as long as no current
is drawn from the intermediate power rails. I will be using +/-5v for
some things (pot voltages, analog switch power, etc.) so I will keep the
+/- 15v currents probably below an amp each.

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?

If I wanted to do the same thing with the +5 volt-only supplies, the
same concept would apply, except the total current would be 3 amps and
the number of cascaded supplies would be 6.

I realize that the final, definitive answer to this question would be
easy to achieve via strictly empirical methods (i.e. try it and see!)
but I figured that it would make for some interesting DIY discussion.

 - Gene