The integrated circuit used in this application is uncommon today. The circuit converts capacitances into voltages from 1 to 10 V for a capacitance range from 10 uF to 100 uF.
I found this simple circuit in an English magazine from 1984. The circuit can be assembled easily...
This circuit is from the 1972 RCA Linear Integrated Circuits Manual but can still be easily...
This passive loudness control was obtained in an old publication. The critical component is the...