"Stacked" Power Supplies - any thoughts?

Stopp,Gene gene.stopp at telematics.com
Tue May 19 23:09:00 CEST 1998

Regarding the commutating filter, I intend to find out what it sounds
like! I did test it out when I built it in the lab back at my old job
(lots of spare time right before we closed the doors on the place) but
it was listening to a sawtooth wave from an HP function generator into
the gizmo over headphones. I remember the impression that I got was very
flanger-like. But I reeeeally want to see what it sounds like with a few
VCO's into it, and maybe some nice crisp white noise. You may remember
that it basically consists of a pair of switched-cap integrators in a
state-variable configuration, with a dual pot where the two integrator
R's  would normally go and labelled "Bandwidth", plus a Q control....

I hope it's weird.

Regarding the power supply thing, I'll probably try decoupling at the
loads, or at the far end of the rails, or some combination of that. It
would be interesting to see if the compensated feedback loops work with
each other and be stable, or against each other and ring and wobble.

 - Gene


Don Tillman wrote:

Hey man!

   a VC commutating filter

I've always wondered... what the hell do these sound like?

   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
   from scratch. However, I have a box full of Power-One +5/-5 supplies

   My question is about regulation stability - can this be an issue?

Yeah.  The "contract" of a power supply is to maintain a constant
voltage between points A and B, and degrade gracefully from that under
stress.  (Since they use feedback loops, and feedback loops need to be
compensated for, one form of degradation is how the unit handles
sudden current transients.)

In your proposed setup, the power supply is no longer providing the
+15V line, it's supplying the difference between that and the +10v
line (which is likely a value you care less about).  So any induced
noise on the +5v or +10v lines will show up on the +15v line.  Given
that you're likely using the +5v line for digital logic, I think this
would be a bad thing.

  -- Don

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