sallen key butterworth interfacing with arduino Due
If you can modify your circuit, you can remove R15 and then take the output from C6 and add a simple DC bias circuit as described. C6 will already "isolate" the circuits. You have to make sure not to set R11 too high.






simulate this circuit &ndash; Schematic created using CircuitLab

If you can't modify the stethoscope circuit, then you can simply add another capacitor like C6 from the output, essentially like the circuit in this answer.