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| Thread ID: 120570 | 2011-09-15 03:49:00 | Mysterious audio phenomena | george12 (7) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 1231161 | 2011-09-15 03:49:00 | Last night I experienced an interesting audio fault in which, with my headphones connected (plugged in securely), I would hear what sounded like one channel, but through both speakers. Parts of songs would be missing, for example, no drums, or no lyrics (not missing entirely but almost inaudible - kind of like a cheap karaoke machine). Both speakers would emit sound at equal volume. The balance in Windows was normal - 100% both sides. I found that if I turned either side DOWN to zero, it would sound approximately normal (presumably mono but nothing missing). Now, I find I can reproduce this on my stereo (when connected to my laptop) simply by slightly unplugging the 3.5mm plug at the stereo end. This seems odd to me. I imagine this slight unplugging is disconnecting the tip (left channel I believe), in which case I would expect the left speaker to simply be silent. But audio of equal volume still comes from both speakers. Furthermore, when the plug is plugged in correctly, the sound from both speakers is indistinguishable to me. There is no clear separation in which the previously missing components come from one speaker and the rest from the other. I don't understand why I get the full sound in this situation only when I set the speakers to DIFFERENT balance levels in Windows, either. I'm thinking perhaps that the stereo is picking up the signal BETWEEN the right and left channel and using that. Is this possible, and would it explain it? I'm really just curious what could possibly be going on. It's worth noting that even in a pair of analog, normal headphones, the sound is not noticeably different in each ear. In contrast, when the 'phenomena' is occurring, large components of the music such as both drums and lead singing, are inaudible. :S |
george12 (7) | ||
| 1231162 | 2011-09-15 10:35:00 | What's probably happening is the part of the socket responsible for contacting the mid section of the plug is actually sitting in the rut between the tip and mid sections, and basically passing its signal equally to both R&L channels. Meanwhile the channel for the L is missing its contact entirely, and the whisper of the L that you are hearing is crosstalk - either within your system, or from the original recording. It's a theory anyway. |
Paul.Cov (425) | ||
| 1231163 | 2011-09-17 05:40:00 | Thanks Paul - Steve (Erayd) suggested that (as you say) one channel was contacting both channels of the socket, but that the strange effect may be caused by the sound driver reconfiguring the port to some sort of surround sound option, expecting other channels to be connected. This seems plausible. | george12 (7) | ||
| 1231164 | 2011-09-17 12:45:00 | I read somewhere (damn, can't remember where now!) that apparently if you disconnect the ground wire on such a stereo system (as is the case with the plug half out) it will cut out the remnants of the 'center channel' which normally holds vocals (as this is where they are recorded in the studio) No idea if that's true, but testing it on my speakers yields the described result. |
Agent_24 (57) | ||
| 1231165 | 2011-10-20 11:40:00 | I read somewhere (damn, can't remember where now!) that apparently if you disconnect the ground wire on such a stereo system (as is the case with the plug half out) it will cut out the remnants of the 'center channel' which normally holds vocals (as this is where they are recorded in the studio) No idea if that's true, but testing it on my speakers yields the described result. Very belatedly I can confirm that you're right. In fact it is the headphone jack in my laptop that's faulty - it's just that the other pair of headphones I tried have a plug that does not trigger it under the same conditions. However, now it's worsened and I have to apply force to the plug for it work correctly. Very annoying. Laptop is under warranty though. I suspect HP will replace the motherboard for the fourth time (different faults). A lovely laptop the 6930p, but mine has been a bit of a lemon... I should clarify that (to my knowledge) the headphone jack has never had any adverse stress on it (ie. no nasty yanks on a plugged in cord). I would never have expected the loss of the ground to cause such interesting results, but now that I understand it, it makes perfect sense. It could even be similar to what karaoke machines / software does. |
george12 (7) | ||
| 1231166 | 2011-10-20 12:10:00 | May not be the headphone jack itself, possibly the solder joints, worst are the SMD ones - the solder just breaks so easily. Stupid idea, it saves a tiny bit of space at the expense of a heck of a lot of stability\robustness. But what I am getting at here is that if it happens again out of warranty it may be an easy fix. |
Agent_24 (57) | ||
| 1231167 | 2011-10-20 12:37:00 | Thanks. Ah yes, I did mean the solder joints. I've done DC jacks before so if it's anything like that it won't be a problem. If it's SMD it's beyond my capabilities. If it were up to me, the headphone/mic and DC jacks on all laptops would be on a separate little board, which plugs into the motherboard. They'd then be replaceable with no soldering skill. Toshiba used to do that for DC jacks, don't know if they still do. I don't know why others don't. It's extremely common for the DC jacks (or the soldering thereof) to get damaged. |
george12 (7) | ||
| 1231168 | 2011-10-20 13:16:00 | Most SMDs are not very difficuilt if you have some practice. If you can solder through hole parts already you are halfway there. Headphone jacks and such typically have fairly large leads (comparatively speaking!) It's only things like BGA, QFN, and anything else without actual leads that can be tricky\impossible for hand-soldering (requiring hot air or other tools) Pretty much any part with leads can be done by drag soldering (www.youtube.com). Resistors etc with point-to-point (www.youtube.com). (Interesting to compare that method done properly, to this method done badly (www.youtube.com)) Or so it would appear. I haven't really done any of it myself either, but I hope to soon. In any case, the videos are interesting. |
Agent_24 (57) | ||
| 1231169 | 2011-10-21 07:30:00 | I've had the small stereo female sockets get munted just from them holding onto the male part too tightly while it's being withdrawn (sheesh, that's a sentence begging for a bunch of twisted inuendo). The contacts within the female end just bend instead of releasing, so sometimes a good snug contact can be a bad thing. | Paul.Cov (425) | ||
| 1231170 | 2011-10-21 09:58:00 | It's basically cutting out the center channel and summing whats left to mono. | goodiesguy (15316) | ||
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