The integrated circuit used in this' 90s amplifier is not very common today. The supply is 24 V, the gain is 50dB and the input resistance is 100 k. The circuit is from an old circuit manual.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...