This circuit is from Radio Electronics. The magazine no more exists, but the circuit can be assembled easily. Instead of Rx and a low impedance speaker can be used a small radio transistorized transformer. The power supply can be symmetrical 6-15 V. You can connect the output of 741 is also an old transistor radio output transformer to directly power a low impedance speaker. The input is high impedance and the gain determined by the 100k resistor, which can be changed. Power is a few tens of milliwatts.
