# Is it possible to run a small circut off the power that is output from a unpowered headphone/speaker?

So I'm currently dreaming up my first PCB project! I would like to make a 1/4 audio switcher for my current audio setup (two outputs 1 input)

I'm fairly new to electrical engineering I'm about 3 years in but have a grasp on the basics from a variety of projects. However, I'm am unsure of the viability of this one and I don't know where to look for the correct resources on this.

My Idea is to power some kind of capacitor/battery that can then be stepped up to a voltage that can run a small chip like an ESP32 to handle the interactions. I then want to use Mosfets to switch the signal from one side of the output to the other. I was wondering if it was possible to siphon the initial power from the output of the headphone jack to charge some persistence circuit that will maintain this power; and or trickle charge an onboard battery without interrupting the audio stream after a while.

My main concern is that there wouldn't be enough throughput to start to process but I have no idea.

I'm looking to see if anyone can point me in the right direction for this project! The ESP32 has a deep sleep mode the minimizes power consumption and Im under the impression that this might be possible just due to the fact that driving headphones must take some power. Worst case ill just add a USB connection but I'd rather not go that route.

If anyone can help it would be super appreciated I feel like this would be a great way to expand my knowledge of electrical engineering!

• siphon the initial power ... what is initial power? – jsotola Apr 7 at 0:54
• by that, I mean the power that would normally control and power the speakers in the headphones – Echo Apr 7 at 0:55
• that would be the audio signal ... it is continuous, not "initial" – jsotola Apr 7 at 1:00
• yes! that is correct but im trying to have it use as little as possible to avoid interference with the audio quality and or stop after an adequate charge is made. Also, I'm capable of writing a web app that could blast the audio for like a minute on startup if something like that is necessary – Echo Apr 7 at 1:08
• USB seems like the better choice. – Tony Stewart EE75 Apr 7 at 1:41