Understand 3.5 mm jack in mobiles and laptops, and how to wire in earphone DIY

[You need to understand this before heading to any earphone DIY projects! Once earphone drivers are soldered and shell being ensemble, re-wiring is a very difficult work and may cause none-revertible damage!]

Let’s try to understand with basics

As shown in the image, there are mainly three types of ports. We see mostly TRS and TRRS types jacks.

TS type jack does not support stereo sound and microphone. It means there is no left and right only mono. Both side of headphones will give you the same sound. In headphone DIY, we use TS type jack when connecting left/right speakers separately with 2wires. 

TRS type jack supports stereo sound but it does not support microphone. You can only listen to music but can not make calls with these type of headphones. And this is the most common jack when we DIY earphones w/o MIC.

TRRS type jack supports both stereo and microphone functionality. This is used when the cable with an embedded MIC. 

Now we will try to understand it thoroughly how to wire in earphone DIY. 

By comparing the above two images, one can understand the positions of left, right and microphone.

Now comes the tricky part. When it came time to add in a microphone channel, things went a little pear-shaped because there were two schools of thought on how to wire up the connections. One called CTIA, and another known as OMTP. Some manufacturers chose to change the socket in order to make the sleeve contact as the ground line (OMTP), while others chose to leave the ground contact where it was and squeeze the new channel in on the sleeve (CTIA). It is shown in the below image

So no matter what you have, laptop or mobile phone, your manufacture could have followed either CTIA standard or OMTP standard. It is the reason behind compatibility issue with headphones. So it is possible that your mobile phone headphones don’t work with your laptop or vice-versa.

  • How to overcome this problem ?

Simple. Use stereo headphones without microphone (TRS type). Means having only two strips in jack instead of three. Let me make you understand through image.

As we can see, the position of left and right remains same, it will work with both CTIA standard and OMTP standard. Position of microphone will be covered by ground. So it won’t affect the compatibility. If you only want to listen to music, always buy headphones without microphone because of this you won’t need to worry about compatibility of the headphones.

  • What if you have already bought incompatible headphone but you still want to use it ?

Simple. Buy one of this. It will (probably) solve the problem. Why probably ? Because this item also follows either CTIA or OMTP standard. But it cost way more less compare to headphone. So buy one of them and check if it works. If don’t then buy another one.

 

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