Homemade magnetic amplifiers made from common materials.

More info is available at Homemade magnetic amplifiers can be made from common transformers and toroids. This video shows the control of a car headlight using a potentiometer and a magnetic amplifier made from normal 12 volt transformers. This video also shows an audio magnetic amplifier, made from junk box toroids, being used to amplify the audio signal from a crystal set. Gain is also demonstrated with acoustic feedback between two speakers.