I'm trying to inject additional sound into a phone call. Therefore i modified a basic cable headset to use audio from my iPod.
This is my current prototype circuit:
That circuit is already working, but has some disadvantages due to the very basic passive mixing. When i turn up the iPod's volume it get louder and louder, but it also starts to decrease the mic volume.
Basically I'd like to be able to increase the iPod's volume without affecting the microphone level.
I think it has something to do with the iPod being a low impedance device (around 32Ω i think) and the electret mic being a high-Z device (around 1.5 k – 10 kΩ). Maybe there's also a problem with the power? The mic will only produce several millivolts, where as the iPod can supply more than 1 volts?
How could i improve my circuit, but still keet the headset recognized as a high impedance device. (if it's low-Z, the phone won't detect it properly).
Thanks in advance & bye! Hans