This simple audio and RF signal tracker was found in a Japanese publication in 1967. The transistors are made of germanium and the headphone is made of crystal.
This circuit appeared in a noverber 1962s Practical Electronics. The magazine is no more, but the...
This circuit is from an American 80's documentation. The integrated circuit is from the time and...
Other series amplifiers such as the MC3301, MC3401 and LM2900 can be used on this circuit. We...