Variacs provide a voltage-adjustable source of alternating current (AC) electricity. Usually plugged into a wall outlet (120 volts AC at 60 Hertz in the USA), they have a knob-controlled output that can range from 0 volts AC (VAC) to about 140VAC, depending on how the winding is connected (see below).

What is the main function of a variac?

A variac is a vary simple device to use. It's purpose is to raise or lower the voltage that enters it. Example: If your input voltage is too low – say 105 volts AC, you can just dial it up to the desired voltage, like 120 volts.

Why do I need a variac?

A variac is an excellent tool for safely powering up an old radio or amplifier that has not been used for an extended period of time. Using this low-priced piece of equipment could save you time and money as well as enable you to bring that old piece of equipment back to life with very little effort.