Re: [LAU] lost sound (it had been working)

OK ... well that was very interesting....

I loaded Knopix 5 .1 and the sound worked perfectly right away...and
that's not a very old version ( < 2 years I think). So then I loaded
the Ubuntu 8.10 liveCD and it also worked fine.

So this is not a speaker problem or a hardware (MB "soundcard" problem)
and it's not an old software vs. new software problem. It can only be a
configuration problem.

Thinking of trouble-shooting scenario, I wonder if it makes sense to
reload the liveCD, capture the config and then boot off the HD and
compare what's in place to what worked on the liveCD? If you think
that's worthwhile can you let me know which configuration settings to
capture. Or any suggestions, really.

thanks

Reid

Reid Vail wrote:
> The Mic was a really generic stand-alone 6-year-old component. A mic at
> one end, a 5-foot cord and a jack at the other. Worked fine on a Dell
> laptop (with an integrated socket) but never got it to work with my
> ubuntu machine. Nothing suspicious about it whatsoever (that I know of).
>
> But that is a good idea about the a live-linux CD or knoppix, which I
> also have and might be good for a test.
>
> Thanks
>
> Reid
>
> James Cameron wrote:
>
>> On Tue, Jan 20, 2009 at 04:29:01PM -0500, Reid Vail wrote:
>>
>>
>>> I get nothing at all from the head-phone jack either.
>>>
>>> The funny thing is, this all started when after I tried plugging in a
>>> mic. And that's it.
>>>
>>>
>> That might relate. Was the plugging in successful? What sort of
>> microphone? Was the cable attached to any other device? Have you tried
>> plugging it in and out again? Was the plug tip undamaged? Was it
>> difficult to plug in?
>>
>> A story: this might not be your problem, but it was fun to fix, and it
>> might give you some ideas to explore.
>>
>> Friend of mine bought a laptop, and used it for showing audio and visual
>> content at church. It is an Intel HDA sound device, with three 3.5mm
>> TRS sockets at the front. One is marked as an input, the other two as
>> output. He connected the output to the church sound system, which might
>> have had phantom power.
>>
>> After this, the integrated speakers would not work, and the left-hand
>> headphone channel would not work.
>>
>> Booting and old Linux on CD, Knoppix 3 something, could make the
>> speakers work, but not Windows, and not a modern Linux. Therefore this
>> was a software related problem.
>>
>> The Intel HDA sound system has a Conexant 20549 codec attached, and the
>> codec has electrical sensing of the presence of the headphone plug. Not
>> physical sensing like a switch, but electrical.
>>
>> Since we know the headphone jack is electrically damaged, it goes to
>> show why the speakers are not working ... unless an older driver is
>> installed that doesn't enable the "mute speakers when headphones are
>> inserted" feature. This mute is not an ALSA control.
>>
>> Here is my write-up:
>>
>> "Success. I have the speakers playing and I understand the problem
>> better. I made a change to the Linux kernel source code to ignore the
>> headphones. Here is what seems to have happened;
>>
>> 0. there are two headphone sockets on the front, one is also an SPDIF
>> optical output, and there is a set of speakers on the body of the
>> laptop,
>>
>> 1. electrical damage to the headphone circuit, caused by either
>> manufacturing fault or something peculiar about the church sound system,
>> or static discharge, or power surge between power supply of laptop and
>> earth conductor of church wiring (would be almost impossible to prove
>> either way),
>>
>> 2. the left headphone amplifier section no longer functions, the right
>> headphone amplifier section works fine, (both headphone sockets exhibit
>> this symptom),
>>
>> 3. the left headphone amplifier is used as the method to detect whether
>> headphones are present, since it is connected to the sharp end of the
>> headphone plug, and so a half-inserted plug won't normally trigger it,
>>
>> 4. because the left headphone amplifier section has failed, the
>> headphone detection operates as if the headphones are present,
>>
>> 5. the driver for the sound device notes the headphones are present and
>> turns off the amplifier for the speakers."
>>
>> References:
>>
>> http://www.alsa-project.org/main/index.php/Help_To_Debug_Intel_HDA
>> (developer section),
>>
>> cxt5045_hp_master_sw_put() function in patch_conexant.c source file,
>> comment reads:
>>
>> /* toggle internal speakers mute depending of presence of
>> * the headphone jack
>> */
>>
>> http://quozl.linux.org.au/2008-12-19-hp-present/
>>
>>
>>
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Received on Wed Jan 21 04:15:03 2009