Modding: Sony Ericsson Headset for Samsung Galaxy S 2 / iPhone

A couple of years ago Sony Ericsson had the genius idea to create a mobile headset where customers can plug in their own pair of headphones. No other company (that I owned a mobile of) ever picked up this idea and copied the concept, which is bad. Even worse is the fact that Sony Ericsson uses a proprietary plug to connect headset to mobile which makes it useless for other brands.

I recently returned the company iPhone and got myself a new Samsung Galaxy S 2 smart phone. Well, and since there was no need to use iTunes any more to perform a simple "somehow get some of your music to your smart phone - if you are lucky"- task, listening to music from smart phone was an option again.

To be honest: The headset shipped with the Galaxy is really good but I still do not feel very comfortable with these ear plugs since they all more or less live up to their names and PLUG my EAR. Don't get me wrong, I can imagine uncountable situations (are you married, do you have kids? :P ) where that's exactly what you want but I don't.

To make a short story not longer than it is: Once upon a time I decided to mod my old Sony Ericsson headset to plug it into any phone using a standard 3,5mm 4-pin headphone plug... (I enhanced some of the photos but was too lazy editing out all the shadows and artifacts. But I guess it's good enough to see what's happening)

So, first step was easy: Cut the Sony Ericsson plug from the headset.

Proprietary Sony Ericsson headset plug

Second step was not soooo easy: Figuring out the wiring of both the old and the new headset. After doing some research on the web I found some hints how the Sony Ericsson plug is wired, what wire colors have what function and how the schematics could look like.

I also found some info how this should look like on the Galaxy S 2 and (because I have not returned it yet) on my IPhone 3 GS. It is the same schematics on both. This makes sense because both phones have same 3,5mm, 4-pin headphone plugs/sockets and somebody could have the idea to interchange both headsets (I did, and it workes).

Sony Ericsson headset and wiring:
Copper : Earphone ground (-ve)
Blue: Earphone right side (+ve)
Green : Earphone left side (+ve)
Black : Microphone ground (-ve)
White : Microphone (+ve)

Since I prefer to have proof that my information is right (and I needed it anyway for this project) I bought a 3,5mm, 4-pin headphone plug and started to verify my theories. Finding ground and left/right earphone was easily done by playing some music and connecting the wires using banana clips.

3,5mm, 4-pin headphone plug
Tip: Earphone left side (+ve)
First Ring: Earphone right side (+ve)
Second Ring: Ground (-ve)
Sleeve: Microphone (+ve)

Then I plugged some headphones into the Sony Ericsson headset and used my multimeter to read out resistor values for earphones and microphone both for open and closed talk switch (the button used to accept an incoming call or to trigger voice dial). Same with the original Galaxy headset. This is where I found some differences:

Sony Ericsson:

Resistance of microphone: ~777 Ohm - When talk button pressed: 1,6 Ohm

Voltage over microphone (using diode test on my multimeter): 1660mV in one direction 568mV in the other direction. 85mV in both directions when talk button pressed.

Galaxy:

Resistance of microphone: ~1,45k Ohm - When talk button pressed: 96 Ohm

Voltage over microphone: 1875mV in one direction 629mV in the other direction. 81mV in both directions when talk button pressed.

There are three lessons I learned from these results (and some trial and error):

1. Use a 100 Ohm resistor to correct the resistance when talk button is pressed to avoid (too) high currents
2. Pay attention to polarity when connecting microphone ground and earphone ground (which must be done to connect 5 wires of Sony Ericsson headset to 4-pin plug)
3. Don't care about the difference in resistance of the microphones

The IPhone 3 did not mind when I first got the polarity of microphone/earphone ground wrong (I by mistake connected microphone +ve to earphone ground and microphone ground to microphone +ve but on the Galaxy receiving the call by pushing the talk button and talking though the microphone did not work. Switching the two cables did the trick on both phones.

Galaxy headset resistors with open (above) and closed (below) talk switch.

4-pin plug with soldered wires and 100 Ohm resistor

Put everything together, a knot in the cable works as a pull relief

The whole picture: Sony Ericsson headset/microphone, custom 4-pin plug and earphones of MY choice ;-)

Please leave me a comment if you like this or built something similar to this.

Have fun and let the music take control! ;-)