First, thanks again for the help, and for any more you provide me with : )
"THe "smoothing" in a switched DC converter is a part of the converter in the form of output filters like capacitors and inductors."
So is the smoothing external to the switching regulator or is it a part of it?
It is a part of the regulator, but not the IC because capacitors and inductors are almost always too big to fit onto an IC. Plus they are the most crucial parts to customize in a switching converter. You can get modules where everything is integrated into one package, but they are rare and expensive.
"Try a switch mode IC, they require a few external components and stages. It may not seem related to your original question but if you can variably control the approximate voltage the linear regulator gets you don't waste the heat in the first place"
But how difficult is it to variably control the output of a switching reg?
Dead easy! Switching regulator ICs almost never have a fixed output voltage. THey use a resistive divider that steps down the output voltage to a level tolerable to the IC. This scaled down voltage is then fed back to the regulator so it knows what the output voltage currently is in order to regulate it. The ratio of the resistive divider sets the output voltage of the regulator (relative to the internal voltage reference of the switching converter IC). Just use a potentiomter instead of a fixed resistor divider and you instantly get variable voltage. Really, it's no different than what you do with the LM317 to set it's output voltage, whether it be fixed or variable. By no different, I mean exactly the same thing.
So basically it would go something like this (in my situation):
smoothed variable DC -> switching reg -> smoothing capacitor -> linear reg
Smoothing capacitor is lumped in with the components that are needed to get a switching regulator to work. But that is just semantics. Some linear regulators don't need one to operate, but they aren't switching square waves so they don't need to filter them out. THey work better with them, however.
I am not sure what you mean by smoothed variable DC. But the source voltage should be DC and it's better if it is smooth than not- makes the regulator have to work less to produce a good output. They can only react so quickly and supress input noise by so much after all.
So ideally for me, the switching reg would be variable. It would also be just super if somehow they adjusted to each other so that there was one voltage control, that automatically adjusted the switched regs output to be slightly higher than the linear regs.
Depending on the noise requirements of your output voltage, chances are you can get away with just a switching regulator set to be variable. But if not, it's going to be tricky to get the two potentiometers controlled by a single knob and to use it to get the output voltages not to scale proportionally to each other, but to maintain a fixed voltage difference between the two outputs. Sure it's possible, but the extra circuitry required to do that are probably outweighs the benefits. See if you can't just use a switching regulator alone.