posted 23 February 2004 15:28            

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Hi all,

I've been putting up with a little annoyance since I bought my G4 a couple of years ago; maybe someone has a simple solution.

The audio out of my Capy and Mac G4 both go into a mixer. I get a lot of noise from the Mac--I know it's originating from the Mac because it changes depending on what the Mac is doing. Same sort of thing as when I used to put a radio inside my Altair 8800 and enter different length machine language loops to create various pitches. But here's the weird part: if I turn down the volume on the Mac using the mixer, the noise doesn't decrease; but it does if I turn down the Capy! And, it also goes away if I unplug the Mac audio.

Any ideas? Ground loop? Reversed polarity somewhere maybe?

Larry

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posted 23 February 2004 15:36            

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Some thoughts and questions:

* Maybe noise from the G4 is getting into that mixer strip(?) You could test this by moving the Capybara outputs to a different set of mixer inputs
* Are the G4 and the Capy and the mixer all plugged into the same outlet? (If not then, it could be a ground loop)
* Are you using balanced lines on the Capybara?
* Is your mixer balanced or unbalanced?
* Are you using a CRT or LCD monitor. Is it possible that the noise is coming from the CRT?

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posted 23 February 2004 16:49            

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-when I unplug the Capy audio into the mixer, the noise goes away, returns as soon as I plug in anywhere else
-everything is plugged into the same wall plug pair, but not necessarily the same socket of the two
-everything is unbalanced
-sounds like CPU noise; patterned, changes if I launch an app or move the mouse; no difference if I turn the monitor off

Additional comments:
-doesn't matter whether the Capy is on or off
-doesn't matter whether the firewire is connected to the flame
-the capy is in a rack with the mac sitting right next to it, but that was never an issue with my previous mac, and if it was just picking up noise by proximity, I wouldn't think it would matter whether the mac audio was plugged into the mixer or not
-unplugging the capy audio left channel stops the noise in the left channel; unplugging the right channel stops the noise in the right channel; unplugging the mac left or right channel alone has no effect, but unplugging both stops the noise

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