Found in a 1949 Radio Electronics, this 4-tube circuit was fed directly from the mains with a half-wave rectifier.
This circuit makes use of a sensitive 5 mA reed-relay to be driven directly by a phototransistor. The...
This circuit was found in a 1967 RCA manual. The transistors are of the time. The adjustment is made to...
This powerful amplifier was part of commercial sound circuits from the 90s. The integrated circuit...