This circuit from the 1980s uses an operational amplifier that is uncommon today. The circuit can be designed with modern operators. The gain is 40 dB.
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...