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.
Using power transistors of the time, this source was published in Radio Electronics magazine in...
Found in an American publication on transistors from the 60's, this circuit uses a transistor...
This circuit is from a very old publication, from the 60s. It uses germanium transistors from the...