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 power source was found in an old Argentine publication from 1973. The transistor could be the...
With this circuit it is possible to monitor a signal that is being recorded on an old tape...
This circuit is from a 70s documentation. The maximum sampling rate is 800 Hz. The operational...