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.
With this circuit it is possible to use a common hair dryer as a hand dryer. The circuit is timed...
This circuit was obtained from an English magazine from 1979, but can be easily assembled today...
This circuit was obtained in a 1975 magazine, but it can be easily assembled using BC548...