This high-impedance headphone circuit was found in a 1990s William Sheets. The power is low, but the high input impedance makes it useful for radio applications.
This circuit for model making was found in an English documentation. The SCR can be the TIC106, and...
This circuit was found in the October 1993 Electronics Now magazine. The output transistors form...
We found this touch control on a Popular Electronics from 1970. The circuit makes use of an...