This circuit is from an Electronics World of 1968. The transistors are of the time and the power is supplied with a voltage of 40 V. The circuit is high fidelity.
The integrated circuit used in this project is not common today, but it can be implemented with more...
Found in an American publication from 1969, this circuit can be adapted to be used as a shield....
This current meter with many scales was found in a 80s American documentation. The operational amplifier...