Microphone level sometimes is too low

[cmhodge]

Hi,
Audacity is great and thanks to all who helped make it! I've been getting pretty good results using my computer's built-in condensor mic (its on the monitor so no noise from fans etc). However, sometimes I will find the input is too low, no matter how high I slide the input level. It seems to do this at random. Any ideas why this could be? Is it likely my low-budget sound card? The funny thing is that when it is low, it is not completely off. I can make recordings when it is in low mode, only they are not nearly as good.
The other night I recorded a track, added an effect (classic reverb), and exported an mp3, and everthing was fine. Then I tried to start a second recording, and the mic was in "low mode" even though I did not knowingly change anything in Audacity or in the control panel. I could not get levels up no matter what I tried. The next day I started Audacity again and all was well.
Running Windows XP with some old Creative card.
thanks,
Chris

[waxcylinder]

Could be a bad connection / dry joint somewhere in the chain.

WC

[steve]

Is the microphone "boost" selection in the Windows Mixer enabled?

[cmhodge]

Steve, the boost checkbox is checked. Waxcylinder, it's possible you are right about a bad connection somewhere, but I would expect in that case the signal would cut out completely, rather than just going to a lower level?
BTW, I probably should have been more specific about the low level- it's probably about 20% of the strength of the signal when I don't have the problem.

[steve]

it's possible you are right about a bad connection somewhere, but I would expect in that case the signal would cut out completely, rather than just going to a lower level?

Not necessarily - condenser microphones us a bias voltage to power an internal FET, if that voltage is lost you will loose most of your signal but you still may have a little creeping through. The same would go for any other "gain" stage.

I would check that all connections are seating nicely (take the sound card out and put it back in again, and the same for any other sound card connectors). If that made no difference I'd try an external microphone to see if that was the problem. If still the same I'd try a different sound card.