My setup is as following: I use a Y-Cable for splitting an audio signal to two devices (boxes and earphones). The headphones have quite big speakers so they act also like a microphone - feeding back the signal to the boxes which then amplify the crackling signal.
Initially it sounded pretty easy to me, but it got more complicated than I thought. Additionally, I'm still not sure if there is a problem with the linearity of components up to 20kHz.
The idea was to use a Schottky diode in between the two devices, so none of them could back-feed the other. Unluckily the signal is only 250mV, so even a germanium Schottky diode with voltage drop of 0.2V is not so optimal.
Are there other solutions which are ideally passive or semi-passive by using a small part of the signal for their independent power supply? (Multiplying voltage until its common 5V and using only a few nA) Ideally kind of a low signal diode: If the same principle works for big signals, there should be a way making it work also for small signals.
Or maybe a second reverse diode which will lift the "signal voltage drop" back up? For this I thought a logic connection that has a diode attached, but the logic chips need their own power supply.
What could be a simple circuit?
Other searches: What I found using electronics between audiojack, was pretty sparse: One was the use of Schottky diodes (for bigger signals), the other was this (but not so related): http://www.instructables.com/id/How-to-Harvest-Power-from-an-Audio-Jack/all/?lang=de
