As the name implies, a device that regulates or controls the voltage in a system. The idea is it can take input from a source of voltage that may vary (such as the output of a typical electrical outlet) and output a constant and steady voltage. High quality voltage regulators can significantly improve the performance and reliability of an audio or video system. In order to regulate voltage a regulator must be able to monitor both input and output voltage and have a method of changing the output. There are many ways to accomplish this. The most common ones involve some sort of transformer where the regulator can switch between different “taps” off of the windings for the different voltages. Even among those there can be vast differences in how this is accomplished. The number of taps used and the timing of the switching can both have a dramatic impact on its overall effectiveness for a given application. For audio it is best to use units that switch taps only at zero crossings to prevent noise and spikes.