Need help on 3.5 mm TRS audio jack specs for my headphone project

Greetings all,

I want to build a custom pair of noise cancelling headphones that will work with my mp3 player. The way they work is that you have a microphone which picks up external sounds and then sends it to an IC for processing, which then adds specially creating noise to drown out the environment. This is where I run into problems. All of the units I have seen on the market currently require battery power (usually 1 AAA) to operate. I was therefore wondering about the kind of power and signal that a standard 3.5 mm audio jack provides (specifically from an ipod or iphone), because I would like to design a system that relies on the audio port and uses minimal or even no battery power. Also, what kind of IC should I be looking at that will be powerful enough?

BTW, I have read **broken link removed** but its just too big and clunky for my needs.
Thanks in advance,
Allan

Hi,
You have to provide external power supply anyway. The output from the audio jack are left and right channels, and ground, but not DC voltage for powering anything.

You are not going to get enough power from the signal line without phantom power to run the headphone circuit. You will have to provide for batteries or a power line. Phantom power would be possible (I think) but might be more trouble than it is worth.


Torben

Does anyone know actually how much voltage and power I would be able to get from a headphone port on an ipod or iphone? The reason I ask is because I feel that I could find a small enough IC with minimal requirements to be able to use whatever power I can get.


Also, does anyone have any idea how the iphone headphones work? I mean, like when you press the mic/button it sends a stop signal to the iphone, is it just a simple switch?