This circuit filters low frequency noise from the turntable motor. We found it in a 1989 documentation. The font doesn't have to be symmetrical, but it should have excellent filtering.
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...