This trimmer or reaper amplifier cuts the signal peaks at a voltage determined by the zener diodes. The gain is given by R1 and R1 and the power supply must be symmetrical from 5 to 15 V.
This circuit was obtained from a 1965 Radio Electronics. The semiconductors used admit modern...
In the bridged configuration the TDA2002 amplifier can supply 30 W of power at a load of 4 ohms...
This circuit converts a high voltage into a frequency using an optical coupler. The transistor can be 2N2646...