On Mon, 14 Jan 2008, Gene Heskett wrote: > On Monday 14 January 2008, Bill Unruh wrote: >> On Mon, 14 Jan 2008, Tom Enderlin wrote: >>> Hello, >>> I'm having a heck of time trying to figure this out and could really use >>> some help. >>> >>> Problem is that I'm able to use an old (crappy) labtec microphone, but the >>> two different headset microphones I tried, don't pick up a thing. >>> I've tried the headsets on another computer so I know the headset mics are >>> working. >> >> Does the labtec have a battery? It sounds like a power issue. An electret >> mic needs a power source, and it may not be getting the right power. > > The electret condenser mics do need a battery, but lets clarify something > here. They need the battery to run a buffering amplifier which converts the > many megohms source impedance of the mic capsule down to something that can > be fed down a cable and into a <=50k ohm load of the typical mic input. The
Agreed. But they need power. A buffering amp with no power does not do much. > capsule itself is permanently charged to a quite high voltage, which is where > the 'electret' in the name comes from. FYI, its ultimate high pressure sound > level response, if one were to record a gun going off, is generally such that > a 44 magnum can be recorded without clipping from a point 6" below the muzzle > of that formidable arm. The buffering amplifier in it would probably clip at > a much lower spl. The original condenser mic I've some experience with, an > Altec M-21, could do that to a civil war cannon, and did so for the Mercury > recording of the Overture of 1812 50 years ago, but needed a plate voltage of > 150 volts applied to the 6AT6 tube used as that buffering cathode follower to > do that. Which was the std voltage used also for the condenser bias since > this predates the electret technology by about 35 years. More recent, and > several hundred dollar cheaper electrets, of the teeny AAA cell battery > types, will limit the clip point to about a volt of output, which I can > easily do with my voice. > > I also have 2 varieties of headsets that I use with skype and friends, that do > not have any batteries in them and work just fine. In fact I've not seen any The Mic input on soundcards have power -- try putting a volt meter across the gound-> live inputs of the mic input to the soundcard. Unlike the Line in. Ie, they do not need batteries but they do need power. Now if his mono had a battery it would not need the power from the soundcard, while if his other mic did not, it would. Note that it is his mono plug that works, and his stereo that does not. > for sale at Staples, circuit city, wallies, et all, that do have batteries, > so I'm inclined to think its more likely the OP has a jack incompatibility > such as can happen when plugging a mono circuit plug into a stereo jack and > one side of the stereo is shorted out by the mono plugs contacts not being in > the right place on the barrel. That has been the case for me a few times. Except it is the stereo plug that does not work and the mono that does. > >>> Hardware: ALC888 on a Shuttle XPC SN68SG2 using the snd-hda-intel driver >>> with a model=6stack-dig option. >>> All the other functions on the soundcard that I've tried are working. >>> >>> Software: Debian unstable. Tried both the debian packages (Alsa 1.0.15) >>> and compiling Alsa 1.0.15 from source. >>> >>> Tried moving all the mic and mic boost sliders in alsamixer to their max >>> settings and it still didn't record any audio, just background static. >>> >>> Also plugged the mic into the line-in jack on the back of the computer and >>> same thing: the old labtec mic worked but the newer headset mics didn't >>> >>> I'm totally at a loss here. The old microphone has a plain mono plug and >>> the headset has a stereo plug but I didn't think that should matter since >>> it's just a mono signal anyways. This is a new computer so it should >>> definitely be able to accept an off the shelf headset. > > But if it is the sort that parallels the stereo right at the input jack, the > mono plugs longer sleeve with cause the ring contact of the tip,ring,sleeve > type jack to short the signal out. Gently pull the plug out slowly, testing > as you do, and I'd bet a bottle of suds you'll get something at some point. > >> Depends on the soundcard, but the mic in input on some have the power on >> one of the stereo pins and the input on the other. If your mic is not wired >> up for that, it will have trouble. >> >>> Looked around and found various asoundrc files with input configurations, >>> but nothing has worked so far. Tried all the different snd-hda-intel >>> module options with no success. >> >> If the labtec produces sounds into the mic in input, then it is not a >> soundcard/alsa issue, it would seem to me. >> >>> Any ideas at all would be appreciated. >>> Thanks. >>> Tom > ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ Alsa-user mailing list Alsa-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/alsa-user
