Standard LM386 Audio Chip. Place A Jumper Wire Between Pins 2 and 4. The Pin Connections are indicated in the Schematic
This is a standard 8 Ohm mono earphone or headset
Any, On / Off Switch Will Do - connecting the + side of the 9 volt battery to the circuit
9 Volts D.C. Connect the + side of the battery to the circuit, the Negative side to ground
This Unit incorporates Two standard Radio Shack PART NUMBER # 090 Electret Microphone elements. Actually, two of these elements in parallel produces double the input gain. More than two produces a loss - so stick with the schematic.
Turn the On/Off Switch On. Adjust R11 for a confortable noise level. This is an extremely quite (Internal Noise Level) amplifier and open for a great deal of experimination such as - used with parabolic dishes, etc.
This High Gain listening circuit is extremely sensitive and very powerful. It is used in spy or surveillance applications for gathering a very weak audio signal and amplifying those small signals to a high level. The audio is boosted by two low noise FETS and then fed into an LM386 Amplifier circuit. Once amplified the audio is fed into a set of 8 ohm earphones. The gain of the amplifier is controlled by R11, a 10K pot. All components are listed below.