Audio Amplifier with Very High Gain

This audio amplifier project utilizes a small input signal of 700uV RMS to driver an 8 Ohm speaker or phones to an extremely loud level.

The aluminum case has a total dimension of 3×2.12×5.25in as the unit is being driven by two 9V batteries. The elimination of frequencies below 100Hz and/or above 1,600Hz is made possible by the 2 switches. This amplifier is also very well suited for use with any Crystal Set or other low signal output device although it was designed to be used with the parabolic microphone. The signal should be taken from the RCA jack and fed into the microphone input of a tape recorder if tape recordings are desired.

During construction, the aluminum case is drilled with holes. All components are mounted and soldered on a PCB. Before mounting to the case, the components such as pots, jacks, switches, etc. are soldered to the respective connecting wires. The ground strap and RCA jack are pre-mounted to the case. The switches and other components are then installed into the case. To mount the PCB into the aluminum case, tapped nylon stand-off insulator posts were used.

Rest of the project