Hi Keith,

In message , Keith G
writes
I've started messing about with open mic recording and am having a gas with
all the usual humming, swearing, neighbour's lawnmower, birdsong etc.
accidental recordings but I'm also getting a little thump once in a while
which looks like this on the recording:

http://www.apah69.dsl.pipex.com/keith_g/show/glitch.jpg

Try plugging the microphone directly into the soundcard mic input, and
remove the little battery box that it normally plugs in to. It would at
least eliminate that as a possible source of the problem. It should work
from the plug-in power from the microphone input, but probably it will
give a lower output. I haven't opened it up, but it's probably just got
a pair of panasonic electret elements, in which case the battery box is
optional when it's feeding a PC sound card.

You never know, I might have sent you a dud!

It's very likely the thermostat or boiler which are both brand new and
therefore quite silent, so I haven't been able to catch it 'at it' yet but
what's mystifying me is why does it drag the waveform down which then takes
about a 1/4 of a second to recover? It's nothing like a scratch (or the
tower of crap the old boiler used to add in to the proceedings) and
therefore damn near impossible to remove!

The only other thing that comes to mind is if you have a temperature
dependent fan in the PC, it could be putting a drain on the PSU when it
starts up, and messing with the power to the sound card. Sounds
unlikely, but I've had similar problems with moody PC power supplies in
the past when fans have got stiff.

--
Regards,
Glenn Booth