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/ > > _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
