Stereo heaphone doesn't work properly when the balance is centered

Question

I have an old headphone (Philips SHP1900) and it used to work fine, until the day which I accidentally stepped on it... Since then, when I listen to music, the instruments sound really loud and the voice sounds like it's far away.

First I thought that the problem was at the jack plug, but I replaced it and the problem persisted. Then, after a while, I figured this out: if the balance is in the middle the sound is wrong. When I set the balance all the way to the right, I get the right channel sound from both speakers; the same happens if I set it to the left (left channel on both speakers).

Well, I checked the whole cable, bending it to see if the sound gets back to normal if i bend it but found nothing. Next step then was to check the wiring inside the cups.

All the articles I read said that the if the left and the right wires are touching then all you're gonna get is mono. So imagine my surprise when I opened the left cup and founded that the green (left) and the red (right) wires are soldered together in the same spot...

Wires connection inside the left cup - sorry for the low quality...

I don't know what could be causing this odd behavior, or if the fact that the two wires are together could be the reason (I doubt it because they came like this and it used to work...).

Does anyone know I can fix this?

Any help is appreciated!

It's not entirely strange for colors to change on an internal connection like this, and it probably isn't causing the issue. I suspect a short within the cable itself. — Ignacio Vazquez-Abrams, Dec 01 '14 at 00:58
Hint: What is it that strips vocals from audio when a 1/8" audio jack is partially unplugged? (or you step on your headphones, introducing a similar fault) — Phil Frost, Dec 01 '14 at 01:38
I suppose the cable with green, red and blank comes from the plug, goes to this side of the headphone and the other one with just read and blank goes to the other ear. In this case, the solder point for green/red just serves as a connection between these and has no other purpose on this ear. — glglgl, Dec 01 '14 at 10:03
Actually there are "specific troubleshooting steps" described in the question. They show some effort and go far enough to identify the approximate problem. — , Dec 02 '14 at 14:18

score 7 · Answer 1 · answered Dec 01 '14 at 01:38

Broken earth connection between headphones and plug. Earth connections on both phones are connected to each other, but not back to the amplifier 0V.

Balance fully right, the L channel outputs 0V and you get R channel sound from both speakers (they are simply connected in series, from active R, to L acting as 0V).

Balance fully left, ditto.

Balance centre ... both ends are driven with mono (L+R) signal, so both ends see the same voltage, so mono signal (vocals!) disappear. What you hear is L-R, i.e. only the stereo component.

Great way to turn any CD into karaoke...

Now you have to find out where the break is between the two copper coloured wires in the photo, and the sleeve on the plug, and repair it...

Don't worry about the 2 colours connected together. I can't see from the photo but it looks like the left cable goes to the plug, and the right cable just takes signal to the other earpiece, and the join you see is just a convenient way to make the connection.

Stereo heaphone doesn't work properly when the balance is centered

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