This 300 Hz to 3.4 kHz filter was found in the May 1989 Radio Electronics magazine. The circuit requires a symmetrical power supply.
This circuit is from European 90s documentation. The integrated circuit used is not very common...
This circuit was found in an Electronics World magazine from 1990. The circuit can be mounted...
This circuit can source 3 to 12 V with currents up to 500 mA depending only on the transformer....