[drambit]

I don't even understand what is happening so I'll just explain the situation. I've been fixing headphones for friend of mine for a few months now, and yesterday a friend of mine came to me with a pair of Monster DNA earbuds (they look like this: http://ecx.images-amazon.com/images/I/41vzozWd0fL._SY300_.jpg). He said that the jack was broken and that wiggling the cable near the jack would cause audio in the left channel to drop in and out. This is a common problem with headphone jacks so I cut it off (these jacks are impossible to open up) and soldered all the loose wires to a different jack I had lying around (it's a 3 ring jack btw, there is an in-line microphone.)
 
After soldering the cable to a new jack, I managed to fix the problem of audio dropping randomly in and out, but the audio was very noticeably muffled, in a way that I can't properly explain, it just really didn't sound right. I started playing around with things and discovered that on the in-line mic there was 3 buttons, one for volume +, one for volume -, and another one that I have no idea what it is supposed to be for, but pressing it instantly makes the audio sound very good and completely removes any muffling that was happening before. Here's what the little in-line remote looks like: http://ecx.images-amazon.com/images/I/41opFINqJwL.jpg 
 
I tried removing the mic wire from the headphone jack so that the in-line remote wouldn't do anything, but instead of making it never muffled it made it always muffled, and pressing the button doesn't fix it anymore, so I'm really really confused as to what is going on with this. I'm not even sure what the button was originally intended to do, but I imagine it isn't this. 
 
Can anyone here help me understand what's going on here? It's blowing my god damn mind. 

 

[Music818]

The center button is for pick up call, together with the "+" and "-" buttons. You don't need to take care too much. Just keep in mind, there should have four wires. One for the right driver "+", one for the left driver "+", one for remote (pick up call, volume +/-), the last one is common ground. Sometimes, the remote (MIC) will go with an individual ground. Then, there will be five wires. The connection may be wrong in somewhere, use a DMM to measure the resistance across the wires would help.

 

[drambit]

It's a 4 wire setup, Right signal, left signal, in-line, and ground. Even if connections are bad though I don't understand from a theoretical point of view how its possible that pick up call button toggles between heavily muffled sound and normal sound. Also the volume +/- buttons don't do anything. 

 

[sek@]

Is it possible that you mixed up the ground connection with the (fourth) button wire?
This could explain the improved sound while the button is pressed down (i.e. with depressed buttons the audio return currents would then flow through the digital circuit that normally serves the buttons).

 

[DingoSmuggler]

  Is it possible that you mixed up the ground connection with the (fourth) button wire?

Agreed. The symptoms fit this cause.

 

[drambit]

  Is it possible that you mixed up the ground connection with the (fourth) button wire?
This could explain the improved sound while the button is pressed down (i.e. with depressed buttons the audio return currents would then flow through the digital circuit that normally serves the buttons).

Oh I might have, there is 4 wires, blue, red, bare copper, and white. I assumed copper was ground but I'll swap it with white and see what happens. Why would it work at all if not grounded though?

 

[dprimary]

The third button is likely to be pause and play. Can't you meter out the connector you cut off to find the correct wiring?

 

[DingoSmuggler]

  Oh I might have, there is 4 wires, blue, red, bare copper, and white. I assumed copper was ground but I'll swap it with white and see what happens. Why would it work at all if not grounded though?

With the mic and ground swapped, the return path for the headphones channels will go through the mic's internal circuit and back to ground, which will add upwards of 2k-ohms of series resistance. The remote button will short out across the mic and ground therefore providing (close enough to) a proper ground for the headphones so that's why you experienced the improvement in sound with the button pressed. Disconnecting the mic wire took the button out of the circuit, so there ground connection was not being made with the button presses.
 
In actual fact, you may have wired the headset correctly IF you are testing this from a standard headphone mini jack and not a smartphone, tablet, etc. A lot of stereo mini jacks will connect to the Sleeve section of a TRRS jack, which is the Mic connection for headsets - in these cases you'd need to use a TRRS to TRS adaptor if you wanted to use TRRS headsets from that player/amp/device.
 
For the TRRS conection, it should be as follows.
Tip: Left
Ring: Right
Ring: Ground
Sleeve: Mic
 
Some early non-apple devices will have had the mic and ground the other way around, but anything in the last few years will have followed apple's way of wiring a TRRS. This is my current understanding anyway, nfi where I would've originally sourced this information from years ago 

 

[sek@]

This sums it up pretty nicely.
 
The main culprit likely is the difference in configurations between manufacturers and generations...

 

[drambit]

  With the mic and ground swapped, the return path for the headphones channels will go through the mic's internal circuit and back to ground, which will add upwards of 2k-ohms of series resistance. The remote button will short out across the mic and ground therefore providing (close enough to) a proper ground for the headphones so that's why you experienced the improvement in sound with the button pressed. Disconnecting the mic wire took the button out of the circuit, so there ground connection was not being made with the button presses.
 
In actual fact, you may have wired the headset correctly IF you are testing this from a standard headphone mini jack and not a smartphone, tablet, etc. A lot of stereo mini jacks will connect to the Sleeve section of a TRRS jack, which is the Mic connection for headsets - in these cases you'd need to use a TRRS to TRS adaptor if you wanted to use TRRS headsets from that player/amp/device.
 
For the TRRS conection, it should be as follows.
Tip: Left
Ring: Right
Ring: Ground
Sleeve: Mic
 
Some early non-apple devices will have had the mic and ground the other way around, but anything in the last few years will have followed apple's way of wiring a TRRS. This is my current understanding anyway, nfi where I would've originally sourced this information from years ago 

Oh that must be it then, because I metered it out and wired tip to left, ring to right, second ring to mic, sleeve to ground.