Found in a 1949 Radio Electronics, this 4-tube circuit was fed directly from the mains with a half-wave rectifier.
The 1: 1 transformer on this circuit found in a 1967 Electronics World can be wrapped around a...
This simple stage can operate with low frequency signals (audio), driving a small lodspeaker....
This circuit has a gain of 6 and a Q factor of 8.63. Operational amplifiers are common, like the...