Question on headphone jack

[armus2112]

I put on my Sony headphones plugged into my second-generation iPod Shuffle this evening. "I Can't Tell You Why" from the studio album started playing. But it was ONLY the rhythm guitar. There was -- no singing, no bass. Just the guitar. Like I was hearing the raw guitar track from the studio. After 20 seconds, I could barely make out the vocals "Look at us baby..". In fact I didn't even know it was "I Can't Tell You Why" until the very faint vocals started. I then jiggled the headphone plug and made sure it was inserted all the way and I could ear the song as normal then.

I was perplexed. How could I only be hearing the guitars and all the rest of the instruments were nearly completely absent (very faint).

Later in the day, I listened to the song on my computer, thinking maybe it was the left track or the right track and the headphone jack wasn't plugged in all the way. But no - the left/right tracks contain more than just the guitars.

What was going on there, anyone know? I thought there were only 2 tracks on a stereo mp3.

[Annoying Twit]

Probably what has happened is that there's a short between the two channels. If you add together two channels out of phase (one side has the signal turned upside down) then anything in the centre will be cancelled out, and you'll hear other instruments. It could happen that there's a short so that you're only hearing one channel. You should still hear the other instruments in taht case, but if the one channel has the rhythm guitar mixed into it, then it may be loud enough to mask the other instruments. (You can't hear the others because the rhythm guitar is drowning them out - easier than it sounds because of the way that the ear works.)

It could be that you didn't have the plug inserted properly. It could be that your headphone socket is broken. If your headphone socket is broken it may or may not be repairable for a reasonable price.

[armus2112]

OK this is cool. I managed to capture this effect to my computer by not fully pushing in the jack into the audio plug. I captured these samples of what I am talking about.

http://twqwctf.github.io/icanttellyouwhy.mp3

http://twqwctf.github.io/takeiteasy2.mp3

[Annoying Twit]

That sounds what you'd expect to hear with phase-inverted mixing of the left and right channels. You can hear the other instruments a bit, but some are increased in volume.

Looking at I Can't Tell You Why in an audio editor, the two channels appear identical, except that they are phase-inverted (AKA upside down). So, there will be some cancellation, and possibly it's only one channel that is present in the output. As the same thing is playing out of the left and right speakers but out of phase, then depending how you're listening you'll hear different cancellation.

[armus2112]

Wow, using Cool Edit Pro, I was able to reproduce this effect. I copied the right channel and inverted it and then 'mix-pasted' it into the left channel. Then I did the same thing, this time from left to right.

The result is what I am hearing from the iPod.