In rec.audio.pro, (Charlie Hubbard) wrote:

On 1 Oct 2003 08:52:46 -0400, (Mike Rivers) wrote:
Try recording a CD on your computer through the same path (less the
phono preamp) as you're using for your turntable and see if the noise
disappears. If it doesn't, you need to do some optimizing on your
computer. This mostly involves turning off things that might
momentarily interrupt the recording process and playing with buffer
sizes in the sound card driver. The standard guilty parties are
auto-detect of a CD, virus checkers, and screen savers. Those
constantly check to see if they need to do something, interrupting
whatever the computer is trying to do (write audio data on disk) at
the moment.

Hi Mike. That's a good suggestion. I haven't done exactly this but I
have run a series of 30 minute recordings in which all my equipment
was turned on and the turntable was spinning but the tone arm remained
locked in its cradle. My thought was periodic computer noise would
show up easily against an otherwise quiet background.

Not neccesarily so. If the problem is the recording process losing
samples, as Mike was thinking, you'll never notice with silence
because all samples are (approximately) zero, and you'll never hear a
missed one. A better way to detect this is to record a low-frequency
sine wave for the 30 minutes, and listen to the recorded file for
clicks/ticks, or look to see if every wave is complete and not chopped
up anywhere.
If it's a problem (even if it's not - you can probably speed up
your computer noticably doing this), run msconfig to control what
startups load on boot, and do a websearch for windows startups so
you'll know what each one does. Here's a relevant webpage:
http://www.pacs-portal.co.uk/startup_index.htm

If I knew I was going to learn this much about MS Windows, I would
have learned Linux/Unix and ended up with some useful skills...

So far, I
haven't seen any problems. The recordings are always uniformly quiet.
There is some 60Hz ripple at about -75dBfs and there are even quieter

Expand it and look through the whole file as above...

120Hz spikes (switching power supply is my guess) but I haven't seen
anything resembling the noise I've been calling "buzz". I'm not
particularly worried about the 60Hz ripple. It's 30 or 40dB below the
surface noise off my typical LP. It goes away along with the surface
noise when I apply the Sonic Foundry noise reduction plug-in.

Be careful with those FFT-based noise reduction/elimination
programs, they can eat into and change the desired sound, especially
quiet passages and especially if set to 'full on' to eliminate all
noise.

Charlie Hubbard

-----
http://mindspring.com/~benbradley