"This document describes how to construct a dual polarity linear power supply which can be configured for any positive or negative voltage between 1.2-35V. A power supply is the fundamental building block of all but the simplest of electronic devices. It converts the alternating current (AC) from our wall outlets into direct current (DC) at some specified voltage. Because so many electronic devices need DC to function properly, a versatile power supply is the perfect addition to a hobbyist's collection of test equipment. " from Wayback Machine
"There are two versions of the power supply which are fundamentally very similar. The first is a compact fixed-voltage supply measuring 2.9" x 2.2", which is well suited for applications requiring small size and modest current capacity like TTL logic circuits or op-amp based projects such as active crossover networks. The second is a larger (4.6" x 2.25") variable supply sporting more robust heatsinking, and the regulators are positioned such that they may be mounted to a large chassis heatsink for even greater heat dissipation. And since this version of the supply is variable, it is ideal for experimenting. See the photographs near the bottom where I built one into an ATX power supply chassis."