This circuit allows the "recovery" of weak signals recorded on tape that correspond to programs. The gain is given by the 270k resistor that can be exchanged for a 1 M potentiometer if you want a wider control range. The circuit is connected to the recorder's phone output, which must be at 1/4 or 1/3 of the maximum volume. The source must be symmetrical from 3 to 6 V. The current consumption is very low, which allows the use of batteries in the power supply. It is not necessary to use shielded cable for the input connection as we have a low impedance.
