I have two devices, each with two 3.5mm jacks for the usual audio out / in. I need a way to cross-over between the two, such that the stereo output of one, goes to the mic input of the other. I have looked into and considered other options and (unfortunately), this is the best option for this project. The devices aren't terribly smart (one has no accessible software component, and one is a knock-off RPi). A software solution wont work, I need a hardware implementation. I have looked around and found several related issues, but I haven't found an actual solution anywhere that works. I did rig up a cross-over cable myself which does work, but barely, and with great audio issues. This seems like it shouldn't be that difficult, but the mic works with much lower voltage than the stereo out, so feeding it directly across isn't a viable / good solution.
Any help is warmly welcomed, or something as simple as a usb audio card that can do it (one of the devices is a RPi type board).