Merging AC & DC Signals

How can I merge an AC audio feed and a headset cable into one stereo male jack going into a DC device? I believe that is the issue I’m dealing with. For more info the post listed below may help. Thanks!

https://forum.audacityteam.org/t/recording-a-cell-phone-call/22593/1

Probably something like this:

http://kozco.com/tech/audacity/pix/headsetBattery.jpg

Here’s the forum topic that this image came from: https://forum.audacityteam.org/t/3-5mm-to-external-audio-card-problem/20644/4

Even with a suitable battery supply, the microphone signal may still be too small to drive your stomp box properly.