No subject

[Garry Peirce]

James,
By your description, I'd guess that your problem might be related to your audio 
gain structure.

Whenever gain is used to compensate for low input levels, you are also 
amplifying the noise underneath the signal.
Your amplifier may have the gain to the speakers set too high to compensate for 
incorrect gain staging. This way it doesn't matter what (if anything) is 
entering it, if the amplifier gain is set exceptionally high, you are amplifying 
internal noise to an audible level.

Try to amplify most at the input, and then maintain that level through to the 
amplifier input. 

There of course could be other reasons , but (re)-checking the basic gain 
staging is a good step in any case. 

Maybe someone could (or already does) source for example, a 0db 1kHz tone that 
can be used by AG rooms to test their audio systems (ex. a XAP800 can generate 
this). I would think it would be preferrable, to have a site adjust their 
sending level rather than altering input and room output levels.

AGC on inputs and/or the use of compression (an external device or via using a 
XAP800) can be used to further control the dynamic range so that one does not 
need to frequently "ride the faders". 

Quoting James Miller <millerjw at mailer.psc.edu>:

> I am trying to resolve a major hiss problem with our AG node.  I am
> getting
> a lot of hiss out of my monitor speakers.  I think I have narrowed it
> down
> to a problem with the AP800.  If I disconnect all of my inputs to the
> gentner, the hiss is still there.  When I disconnect the speakers, the
> hiss
> stops.  This tells me the hiss is not coming from cable interference to
> the
> speakers and it is not coming from the MatchMaker/Audio node.  If I mute
> all
> of my inputs, the hiss remains.  If I mute the speaker output from the
> gentner, the hiss lessens, but does not disappear.
> 
> Has anyone had similar experiences?
> 
> Jim Miller
> Network Engineer
> Pittsburgh Supercomputing Center
> 4400 Fifth Avenue
> Pittsburgh, PA 15213
> 
> mailto:millerjw at psc.edu
> 412.268.6073 
> 



GarryPeirce
Network Analyst
University of Maine System
Orono, ME 04469
peirce at maine.edu