This high impedance headphone amplifier was found in American documentation from the 1990s. Any general-purpose FET can be used.
An application for the previous circuit (CB109) is shown here. The central frequency is determined by C and...
This circuit was found in the November 1994 issue of Electronics Now magazine. The circuit is...
This circuit was found in a 90s Silicon Chip documentation. The current of the transformer is 1 A maximum,...