Keith G wrote:

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

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!

Anyone got a clue what's happening?

Clearly you have some interference. What you really need to do is find out
how it is getting in. Replace the microphone with a fixed resistor equal
to its outpout impedance. If the thumps go away its the mic and there's
probably little you can do about it. If it still thumps then its further
down the chain. Try connecting the same resistor straight across the input
to the mic amp. This will eliminate the mic cable. After that you are
into thumps getting in thru the power supply.

HTH

Ian

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

"Glenn Booth" wrote in message
news
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.


OK, thanks for that and to all the others who responded. The problem is not
a serious one by any means - I don't have to play the piece over if it gets
a thump! :-) The simplest way out is to switch the bloody boiler off during
a recording sesh - not hard in this weather!!

"Stephen Goodman" wrote in message
...

"Keith G" wrote in message
...
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

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!

Anyone got a clue what's happening?

How about an old refrigerator kicking in, and causing either a surge or
drain on the power supplied to whatever you've got your mic hooked up to?

When in college in the late 70s all the recordings I made - both in-line
of
LPs and from a microphone - had an occasional warbled chirping noise that
wouldn't overdub the sounds being recorded, but rather sounded very
lightly
in the background. Whether during a quiet spot in the recording or a
Billy
Cobham drum solo, one could still hear this occasional weird sound that
lasted less than 1/4 of a second. It wasn't audible during the recording,
which was really weird. But it happened often enough that I sat and timed
the gaps between, and every time it was just between 12-13 minutes.

When I thought back on this - still thankfully having the fridge though no
longer at college several years later - I figured out timing the kicking
in
of the compressor on the fridge. It was between 12-13 minutes, same as
the
noise. I wasn't however experiencing the noise happening during recording
anymore - and put it down to the wiring in the dorm I was in at the time,
combined with the fridge kick-in and the Kenwood receiver I was taping
through during the entire span of time.

We didn't have surge protectors back then of course. One might wonder if
this would have been caught by one of the kind you can buy today for less
than 20 quid.


Got a surge protector - never prevented a surge yet AFAIK!!! Thanks anyway.

Love your link btw:

http://www.earthlight.net/HiddenTrack

Loads of cartoons taking the **** out of the RIAA and others worried about
piracy etc. and at the bottom of the page is:

"All contents ©2001-2003 Stephen P. Goodman/EarthLight Productions, all
rights reserved."

:-)

"Keith G" wrote in message
...

"Stephen Goodman" wrote in message
...

"Keith G" wrote in message
...
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

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!

Anyone got a clue what's happening?

How about an old refrigerator kicking in, and causing either a surge or
drain on the power supplied to whatever you've got your mic hooked up
to?

When in college in the late 70s all the recordings I made - both in-line
of
LPs and from a microphone - had an occasional warbled chirping noise
that
wouldn't overdub the sounds being recorded, but rather sounded very
lightly
in the background. Whether during a quiet spot in the recording or a
Billy
Cobham drum solo, one could still hear this occasional weird sound that
lasted less than 1/4 of a second. It wasn't audible during the
recording,
which was really weird. But it happened often enough that I sat and
timed
the gaps between, and every time it was just between 12-13 minutes.

When I thought back on this - still thankfully having the fridge though
no
longer at college several years later - I figured out timing the kicking
in
of the compressor on the fridge. It was between 12-13 minutes, same as
the
noise. I wasn't however experiencing the noise happening during
recording
anymore - and put it down to the wiring in the dorm I was in at the
time,
combined with the fridge kick-in and the Kenwood receiver I was taping
through during the entire span of time.

We didn't have surge protectors back then of course. One might wonder
if
this would have been caught by one of the kind you can buy today for
less
than 20 quid.


Got a surge protector - never prevented a surge yet AFAIK!!! Thanks
anyway.

I actually think that it's the line filtering that most surge protectors
perform prevents a lot of that happening - but of course if your home wiring
is less-than-perfect this will not help.

Love your link btw:

http://www.earthlight.net/HiddenTrack

Loads of cartoons taking the **** out of the RIAA and others worried about
piracy etc. and at the bottom of the page is:

"All contents ©2001-2003 Stephen P. Goodman/EarthLight Productions, all
rights reserved."

:-)

Yep. Don't we all have a right to copyright our own original work? The
RIAA and its cohorts have been attempting to take this right away from
people who aren't a corporation for some time. Check out my analysis of the
so-called Music Online Competition Act of 2001 for an example of what
happens when the RIAA - which later withdrew their support for the Act after
public criticism - finds out they can't just force the Copyright office to
change their rules to exclude folks like you and me. These are the guys who
tried to change local zoning codes to prevent people from operating home
studios, for pete's sake.

I'll be adding the 2004 series soon, btw.


--
Steve Goodman
* Cartoons about DVDs and stuff
* http://www.earthlight.net/HiddenTrack
* (with links to Medialine)