Church sound

[David Miller]

Tim wrote:
> 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.
>
>   
Well, I mentioned that I have the same mother board in my home machine.  
I ran some test and have the same problem.  I had in my pile of spare 
parts a pci sound card.  Sure enough this solved the problem.

David