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I'm using an LM386 for voice amplification. The transmitter transmits the signal from the tank circuit on the correct frequency but without voice.
I'm a beginner and a hobbyist and I'm still trying to understand the process.
Perf board:
Test each part individually.
Feed the LM386 output to an audio detector (high impedance earphone, oscilloscope, "line in" on a PC, whatever). Can you hear it and does it get louder when you turn up POT1?
No?
Try biasing the mic capsule properly (like a 2K resistor to +3V3) and see if that helps... You might want to clean up the 3V3 supply for the purpose...
simulate this circuit – Schematic created using CircuitLab
The purpose of C3 is to keep DC bias away from the pot, which would otherwise cause crackling noise as the pot was turned.
If you check the datasheet for LM386 it suggests this input configuration:
One problem with your design is that the bias current which inherently must flow in input pins 2 and 3 have no place to go - there is no dc path to gnd or to supply. These inputs are merely the bases of transistors and thus always need a current flowing when active. Again - there is a diagram in the datasheet. In figure 12 this is solved by putting pin 2 directly to gnd and pin 3 through the potmeter. The reason your microphone is sensitive to "touching" is precisely that it is floating and has no reference to gnd.
You dont specify the type of microphone but as a starter put it between Vin and gnd on figure 12. Maybe that is all what is needed. look at pin 5 with an oscilloscope to check if it amplifies your sound properly.
