[kráftéé]

D wrote:
Hello!
A background (about 50hz) rumble appears in a sound from microphone.
Windows XP SP2.
I tried two headsets (which surely are good). The rumble decreases
if I touch the computer case. I checked the inside of the case, did
not find any improper contacts. The sound card is Creative sound
blaster live ct4830. I tried the latest Microsoft and Creative
drivers. The Creative driver does not output sound from microphone
to speakers at the same time, but only from a recording from the
microphone. How to prevent the rumble?
Best regards,
Dima

What are you recording, I know you state form a microphone, but are
you plugging in something else into the microphone socket? If so that
would be the problem try plugging it into the line in socket.

If it is a microphone then make sure that it is being fully pushed
home, if it is then try another one (they aren't exactly expesinve).

Others have mentioned ground loops etc, but try the easy bit (normally
the cheapest bits) first.

As a matter of fact I get a continual low level 50hz hum from my line
in post unless I actually plug something into it then it dissapears,
so you could also try turning off all ports you are not using before
doing your recording.