Mike Pre Amp
This page shows the layout and lists the components required to build a

Mike Pre Amp (Internal)



Component List


TR1 - BC549.........TR2 - BC559............VR1 - 5K

F.B. - ferrite bead

R1 - 100K.........R2 - 22K......R3 - 10K........R4 - 470 Ohm

R5 - 100K.........R6 - 470 Ohm........R7 - 1K

C1 - 1 UF 50 V.......C2 - 0.1UF polyester.......C3 - 4.7 nF ceramic

C4 - 1 UF 50 V.......C5 - 1 UF 50 V...............C6 - 0.1UF ceramic


This board must be installed inside the set !

Connect it up to the 12 Volt switched supply on the back of the on/off switch.

Do Not Use A Power Mike With This Unit it is already very powerfull !

It will only end up distorting, because it boosts up the mod to a set level and wont go any higher.

The VR is used to set the input level to the set not the mike level into the pre amp.

I designed the pre amp to give the optimum mod level to start with, it acts just like a speech clipper, only it sounds a lot better because it also improves the tone, giving it a really clean sound, and you dont even have to buy a new mike !

If you experience problems with RF feedback (or squeeling), then you will need to add a filter circuit to the audio wires, you can find the RF filter on my technical page


If you build this unit and like it please email me !


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