This active tone control circuit was found in American documentation from the 90's. The transistor can be general purpose or low noise with high gain.
The circuit in the figure indicates when the input voltage exceeds a certain value adjusted by the...
This polarization step for electret microphones was found in an Electronics Now from the 90s. The...
This 13.6 V power supply with 8 A output was suggested by Texas Instruments in the documentation of...