1
\$\begingroup\$

I have a pair of headphones which came with my phone. They're the standard type that comes with a mobile phone - TRSS 3.5mm jack with an inline microphone.

I was listening to Spotify on my phone. I must have yanked the cable too hard one time and now I only get intermittent sound through the headphones, so I have to move the cable with my finger until I get sound again, so I guess there's a weak contact on one of the wires (as it affects both L and R, I'm guessing the ground)

One thing I'm curious about though - when the wire is in a 'bad' position, the sound doesn't cut out entirely. Instead, the MP3 sounds suddenly as if it is playing at a very low bitrate (horrible MP3 artifacting, barely discernible vocals in songs etc). How is it doing this? I was under the impression that if it's an analog signal, the sound will either play, or it won't, or it will crackle. Instead, it sounds as if something has been digitally adjusted to play at a lower bitrate. Is this something to do with MP3 encoding? And if so, how come I can't hear the low bitrate sounds when the headphones are working correctly?

\$\endgroup\$

closed as off-topic by Leon Heller, PeterJ, laptop2d, Chupacabras, DoxyLover Oct 18 '17 at 7:25

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." – Leon Heller, PeterJ, laptop2d, Chupacabras, DoxyLover
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 3
    \$\begingroup\$ If you've broken the common / ground wire then the headphones will reproduce the difference between the L and R channels. Depending on the music being played this can sound terrible, or moderately OK. \$\endgroup\$ – Steve G Oct 3 '17 at 9:53
  • \$\begingroup\$ @SteveG and the vocals will be affected the most because they are "centred" and only the instruments will be easily discernible \$\endgroup\$ – Makoto Oct 3 '17 at 10:19
  • \$\begingroup\$ @SteveG That sounds like the most likely explanation - I know about phase cancellation , M/S decode etc. I was just wondering why it would sound so heavily compressed and artifacting, as if it's revealing details that I can't hear during normal playback! \$\endgroup\$ – TCassa Oct 3 '17 at 11:48
2
\$\begingroup\$

Perhaps it sounds like a low bitrate because that is the perceptual degradation that you are most familiar with and therefore associate with the new form of degradation.

TRRS jack

One of the major floors of the TRS(/TRRS) design is that the connections are placed on one pin (as opposed to e.g. XLR where the connections are on separate pins). This means that the TRS contacts can connect with the wrong contacts inside the female connector, creating odd sounding results.

Potentially what could have happened is that you have bridged two connectors which is causing left and right to be summed into one side of your headphones, which can cause phase and impedance issues. Other combinations of connections could cause a variety of weird issues when you throw a microphone connection into the mix.

\$\endgroup\$

Not the answer you're looking for? Browse other questions tagged or ask your own question.