This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is 1000 M ohm.
This preamplifier circuit for turntable cartridges was found in the March 1994 issue of...
This circuit is from an American 1964 documentation. Transistors of the time are used, but modern...
This siren was found in a 1980s documentation. The circuit makes use of very old operational that were...