If you need a hefty dual-rail supply, this could be the one. I was thinking of using the "Single Knob Throttle" with larger scale layouts (eg, O and G) when I designed this one, but it could obviously be used with "smaller" scales when operating multiple locos or large consists.

Need a dandy lab bench supply? On the positive regulator, simply replace the fixed 270 resistor with a 220 ohm unit and replace the fixed 2.7K unit with a 2.5K pot (DigiKey 450D252-1-ND or 450D252-2-ND). On the negative regulator, just replace the 1K ohm fixed resistor with a 1K ohm pot. The regulators both have short-circuit protection, so this makes a good bench unit. Just remember those king-sized heat sinks.