I think it's doable using a simple resistor based mixer but I'm concerned about audio level drop so I was then thinking of adding an amp either an upgraded COmy or other easily diy'd amp to fit into a mint box or altoids can. But I don't know if the two circuits would react with each other or cause other problems. In my head it seems ok.
Has any one done this or have any suggestions. My two thoughts are to use something in the 1-10k range for my mixer circuit. I'd run the two inputs in parallel with matched resistors on each side or use dp trimmers on each input so I can fine tune the mix before it gets to the amp. (This can be accomplished at the sources with their volume controls easier and cheaper I suspect)
The other option as I have a nice set of Bluetooth headphones would be to mix them then transmit via Bluetooth but I suspect this would be far more expensive.
Thanks any thoughts would be great?