This RIAA equalizer preamp was found in a 1990s schematic. The transistors are an old version of the BC549 that can be used as a replacement. Signal input and output cable must be shielded.
When the voltage exceeds the value given by the zener, this circuit from a 1990 documentation...
This circuit for the 11-meter band, operating at 29.255 MHz was found in a Radio Electronics dated...
Found in a Popular Electronics from the 9s, this circuit has output for RS-232 interfaces and current...