I have 2 audio channels that i am trying to merge into 1. The problem i am facing is that they share a common ground, so when isolating one signal it still picks up crosstalk from the other signal. My main goal is to have 2 separate outs of each channel and a mono mixed out.
Quickest way would be to build a buffer amplifier for each channel. No gain, just provide a hi impedance between the two inputs, this should pretty well block crosstalk. If you aren't too picky, using a couple of opamps, or two channels of a single opamp, setup for a gain of 1, tying the outputs of the opamps together, and putting a small series(500-100 ohms) resistance between the opamp outputs and the summing point should work for you.