Church sound

[Tim]

On Sun, 2009-03-15 at 21:53 -0500, David Miller wrote:
> Well I have used Audacity for 3-10 min recordings in the past but not 
> for hour long recordings.

I have.  It worked as well as short recordings.  Of course, to edit it,
you need to have enough RAM to fit the whole thing in, or it's going to
be painful to work on.

> I put this machine together and loaded FC10 Sat. and verified that
> sound worked, didn't have time to do much testing.  Took the machine
> to the church this morning and did the recording. I was disappointed
> with the results this first week.  There was a high pitched hiss
> throughout the recording.  I don't know what to make of it yet.  I am
> taking the sound directly from our 32 channel audio mixer. Not the
> right sound for a ground loop.

You can still get them with that.  Considering the complications of
connecting different equipment together, and the additional problems a
computer might add, I err towards using audio transformer coupling
between mixers and the computer.  That eliminates the possibility of
ground loops, and makes it harder for other instabilities to introduce
noises.  Getting a simple transformer DI box with attenuator pad
switching to place between mixer and computer might be a simple
solution.

Hiss could be from any number of sources.  If it's like the typical
amateur set-up, people are often using the equipment wrong (e.g. they
turn down the input gain and turn up the output gain, amplifying a lot
of noise as well as the wanted signal).  Remember that mixer level
controls are not at the immediate input and outputs of a desk, there are
amplifiers before and after each of them.  And, like you said, depending
on your tape system, it may be masking it by lack of ability to record
it.

I'd be going in and experimenting at a time that you can do so without
interrupting services.  Take a very good pair of headphones with you,
and a tame victim to speak into microphones while you try things out.

You should take a line out signal from the desk to a line input on your
sound card.  You may well need to attenuate the signal between the desk
and the computer.  Depending on your sound card, it's probably optimal
if you get normal signal levels when the sound cards audio mixer
controls are around 50 to 75% of the way up.  If they're set elsewhere,
you probably need to change the signal level being fed to the computer.
Make sure that you turn off the other input channels on the computer
mixer (microphone, CD, etc.), unhide other channels from the mixer
control GUI so you can check they're turned down.  And do the same on
the real audio mixer (turn the unused channels down, set up input gain
controls so the input and output channel fader levels are around the 75%
mark).

If your mixer has a spare output channel, and you have auxiliary sends
on the input channels, consider running the recorder completely separate
from how you drive a PA system.  The two have different mixing needs.
Sound reinforcement (PA) is adding amplified sound to natural sound.
Recording has only the microphone signals, and doesn't have the
additional natural sound to add to the level.  It may be best to record
from signals before the tone controls, if you're radically changing the
tone controls for the PA side of mixing.

But, despite your best efforts, you could be hamstrung by having a
rotten sound card in your computer.  Many of them have awful input
stages.  These days, mobile DJs that use computers instead of discs,
will often use an off-board USB sound card to avoid some of the noise
issues they get from internal sound cards.

-- 
[tim at localhost ~]$ uname -r
2.6.27.19-78.2.30.fc9.i686

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