[sdiy] most efficient way to get 5V from 12V?

[Danjel van Tijn]

det3 (from STG?) on Muffwiggler had these comments about the decision
for them to use an external 5V source:

"Assuming we use a regulator in a TO-220 package, there would have to
be sufficient surface area to dissipate the heat bled through this
regulator. I just didn't have room on the main PCB to put the right
amount of copper on the board to keep it from warming up. One thing I
also set in stone when starting to work with STG is that an AnyFrame
PCB (which is what the triple VCA, Time Modules, Post-Lawsuit Filter,
Gate Delay and Wavefolder PCBs are in) do not violate the maximum
board size of 3.25" x 4". Doing so would preclude us from having the
option of deploying the same board in multiple formats, either for
distribution or PCBs for folks who want to DIY.

I also have a problem with putting a linear regulator in a circuit
where the voltage drop from one rail to the next is more than 2-3V.
Without getting into the math, the simple fact of the matter is that
the power not consumed in the circuit is dissipated as heat with
respect to linears. The bigger the voltage drop is between rails, the
bigger the power loss in the system. For example, dropping 15V to 5V
would have 10V of drop. Assuming 100mA being pushed through the
regulator, that's a watt of power completely wasted by heating the
surrounding atmosphere. I would much rather put a switching regulator
in place of the linear one, but that has a few drawbacks. The two
biggest that come to mind are noise, and noise. Switchers radiate
noise which can couple into nearby modules, and that's bad. The way
switchers draw power off of the power bus too is noisy - not keeping a
constant pull but slamming on the rails when it needs power. Even with
a local bulk capacitor, it causes the input rail to sag and droop more
than I would want in a modular. Add those issues with the complexity
of design for a switching power supply on the mini-store, and I
arrived at a swift and resounding "no" for a drop-down regulator from
12V or 15V."