This passive loudness control was obtained in an old publication. The critical component is the tapped potentiometer that can be adapted with an external resistor network.
We found this bench circuit in a Radio Electronics magazine from July 1962. The transistors are...
This circuit is from an 80's documentation. The circuit makes use of a component of the era, the...
This Linear Technology circuit can measure currents from 100 pA to 100 uA. The circuit is from the...