External microphone not working

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Greetings from cold but sunny southern England.

Any help with this would be very gratefully received: I'm pulling my
hair out here!

Yesterday I set up Skype on my laptop - worked beautifully.  I was
using it with some earphones and a small clip-on microphone - no
problems with either of them.

This morning I tried using Skype again and the external mic. isn't
working at all.  I haven't changed any of the audio settings since
yesterday, I can't imagine that the socket has been damaged or that
there's a harware fault (I left the mic plugged in in between the two
sessions).  I've tried XPs troubleshooters to no avail.  The internal
mic. on my laptop is fine - and can be used - but I'd rather use the
more directional external mic. if I can get the damn thing working.

I'm using XP professional on a Dell latitude laptop.

Any ideas?


Re: External microphone not working

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These are only generic suggestions, but anyway:

1) Some sound chips have "jack sense" technology. With the
   computer booted, does removing the microphone plug and
   reinserting it, trigger jack sense ? Does a wizard dialog
   pop up, asking you what was inserted ?

2) Have you tried plugging some other kind of audio source
   to the microphone jack ? Like take a line level output
   from a Walkman and plug it in. A line level signal should
   give way more signal than a mic input needs, so you should
   get a response from that.

3) Does the Dell have a mixer control panel for audio ? Is the
   Mic jack selected and not the internal mic ? Is there a
   clickable "Mute" button anywhere in the interface ? Maybe the
   mic is muted.

An electret microphone has three terminals, but might only
really need two of those. The computer provides a bias/power
source signal, like maybe 5V through a 2K ohm resistor. If
the bias went missing, an electret microphone would stop working.
A dynamic microphone doesn't need the bias source, but gives
a much lower output, and you'd need to turn the gain all the
way up, to use one of those. A line level signal plugged into
the microphone port, would likely require you to unclick the
"microphone boost" button in the mixer panel - some AC97
devices have a 20dB boost button, to give more gain for
weak sources. You would not need the boost button, if using
a line level source.

If you know something more about your AC97 subsystem, such as
what chip is used and so on, you might repost your question with
the additional detail. Download a copy of the free Everest
Home Edition, from Lavalys.com , to learn more about your
computer and what is inside it. You can also look at Device
Manager, to see what kind of driver is being used for the

Finally, I think Dell has some forums. I see one here:


Happy testing,

Re: External microphone not working

Many thanks for all that  - I've checked that the mic isn't muted and
have unplugged and replugged the mic a number of times.  I'll try your
other suggestions and see what happens.

Re: External microphone not working

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Another thing to consider, is with laptops, they are always
concentrating on saving power. I wonder if the bias source
got turned off because there is a power saving setting
somewhere for the AC97 chip ?

Just another theory,

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