This balance indicator for stereo amplifiers was found in an 80's Elektor. The components used are common. Zeners are 1.8 V or close to that value.
This old configuration of an audio amplifier has a push-pull two-transistor output stage. Output...
This is the traditional configuration of na Astable Multivibrator using two NPN ttransistor....
This circuit is from 1987 documentation. The operating system used is not common today, but two...