I agree Jeremy. The point is that Lee wants a bench supply with a specific capability. If I was making a fixed supply then the LM338 is an ideal candidate. IF you want full output current to a given spec over a wide voltage range then linear regulators arent going to cut it. All depends on whats required. If Lee wants to reduce his expectations to 0 - 20v at .5A max guaranteed then the LM338 will do the job without overheating across the range. If he wants >1A output guaranteed then the LM338 isnt the way to go.... as the heatsink will be more expensive than the rest of it all together....

There is a secondary issue - is the goal just to produce something that'll 'just about do' or also to learn more about how to design a proper supply?

Irving...