This audio amplifier circuit was found in Radio Electronics magazine from June 1966. The circuit is a commercial RCA type and is powered by mains power.
This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time....
This old oscillator using germanium transistors has a high impedance headphone as inductor to...
This preamp with several inputs using germanium transistors from the time was found in Japanese...