This Public Address amplifier was found in a 1947 amplifier manual. The power supply uses two transformers with two rectifier tubes.
This ultra-low frequency receiver circuit was published in the August 1973 issue of Radio...
In this circuit of the 1980s, the T1 transformer has 30 turns of 28 primary wire and the secondary...
Published in 1988 in Hands On Electronics, this circuit converts the 12 V of a battery into 120 V AC...