Originally Posted by lontas
I have a device with on-board transformerless mic preamps. They have an input impedance of 1.6k, which is too low for my tastes. I would like to raise it to 2.5k or even higher. But it is impossible to get access to the schematics, so I will be manually tracing the circuit.
1) Am I correct in thinking that the input impedance is set by a 1.6k resistor connected somewhere between the Pin 2 and Pin 3 signals?
2) If that is correct, then is raising the impedance really just as simple as raising the value of that resistor? Or is it more involved than that?
Why is that too low for your "taste"? That statement doesn't make sense to me. What is the source imepdance? A lower load impedance will mean more signal loss while a higher load impedance will mean more noise. As long as your load impedance is about 10x your source impedance you should have nearly max signal transfer.
Load loss = 20Log(Rload/Rload + Rsource)
If you are absolutely hell bent you could build a buffer.