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Interfacing intercom / analog line

player80

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Hi,

I have interfaced an old intercom - basically everything works fine but what bothers me is the direct connection of the system with the microcontroller board.
I'm first filtering the DC offset with a capacitor and amplify the signal with an op-amp.

Now I'm still tying the ground of the intercom together with the ground of my system, I'd like to keep them completely separate since I cannot take the power from the intercom to power the microcontroller (as soon as I touch it it will introduce some noise on the audio out line).

What would be a better solution for that?
Using an audio transformer?
Or is there a better (integrated) way nowadays?
 

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