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I've seen many circuits of microphone amplifiers, and some of them have phantom power in them. But usually there is only one input, and if I were to design a mic preamp for two mics, and get the phantom power from the same power supply, how would I separate the signals? Mics and amps and phantom

In the picture above, signal from one mic can easily go to both amplifier circuits through the phantom power line. What kind of circuit would isolate the two mics, but still have the phantom power from the same supply? Or is there a need to design the phantom power somehow to give separate lines for each mic, and if so, how would this be achieved?

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Your red signal wire is actually two wires, carrying a balanced audio signal (when one wire goes positive, the other goes negative). The +48 V phantom power is fed via resistors to both signal lines so there should be no net audio signal at the phantom power supply. The negative side of the phantom power is connected to the cable shield.

The circuit is something like this:

schematic

simulate this circuit – Schematic created using CircuitLab

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