Add Amp 0619 5286

A two channel wireless mic receiver used at my church. One microphone has died, to be investigated one day... The audio levels out of the receivers have always been low.

I have added a one stage one transistor amplifier to the signal just before the level control of the still-working mic's receiver. The stage gain was adjusted and set using a fixed unbypassed emitter resistor. The load resistor was selected to suit the level control value fed from the new stage.

Pip 1 shows the relevant level control removed during feasibility investigation.

Pip 2 shows the circuit during development and test. The BC548 transistor is held in a vice and all the components hanging off it. Power during testing came from an AT computer power supply.

Pip 3 shows the circuit being transferred to a piece of insulated board for mounting in the receiver box.

Pip 4 shows power for the installed amplifier being obtained from the receiver's 9V regulator. Earth and negative supply was soldered to the main circuit board adjacent to the mounting location.

Pip 5 shows the amplifier board temporarily mounted with all wires connected. It works as intended and I now need to replace the mounting tape with screws and standoffs.