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OT: Digital “noise” from G5??
Hi all. A bit off topic here but I figured that someone will have had this issue before and might have some insight into the problem.
I run my home FCp setup audio through an AJA-LA, into a Behringer mixer anf then into a set of powered studio monitor speakers. Pretty standard.
Recently I decided to run the line output from the G5 to a set of mixer inputs on my board. I usually listen to iTunes while doing graphic work and I thought it would be nice to run the music through the mixer so I could listen to it on the “big” speakers/subwoofer setup. When I connect the G5 to the mixer, either through the line output or the headphone jack, there is an annoying “digital” noise that is getting superimposed over the music. It’s being generated by the G5 and will change as I move the cursor across the screen. I have the same problem with a Macbook Pro that we use for presentation support in the field.
The headphone output sounds clean when monitored by itself-not connected to any external device. The “normal” small computer-type speakers seem to sound OK when connected. It’s only when the Mac is connected directly to the mixer that the problem becomes apparent. Could ther be some weird ground-loop thing going on? The noise is definatly being generated by the computer itself since it will change with the actions being preformed on the screen. While the noise is not too loud, it sounds like a square wave and is very annoying to say the least.
I never use the sound right from the CPU for production, only for listening to itunes, but it is difficult to listen to at higher levels.
I’ve also tried passing the line out signal into a matchbox-type level converter to raise the levels to +4db broadcast levels into the board. Same problems just louder now.
Any ideas out there on how to “fix” this?
Thanks in advance.
Tom -
4 Replies
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Running any audio cable right out of the computer gives you an unbalanced signal vs. the balanced signal out of your AJA box. Unbalanced signals are much more prone to RF (radio frequency)noise and AC humm. It sounds like that’s what you’re getting. Try picking up a really well sheilded cable and it might cure the problem.
DRW
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[David Roth Weiss] “Unbalanced signals are much more prone to RF (radio frequency)noise and AC humm.”
We get a similar experience when connecting our HD Cable box to our Plasma screens in the suites. We get an electric hum in the video and audio so we keep that disconnected unless we’re going to watch TV.
Walter Biscardi, Jr.
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This is noise definitely being generated by the Mac itself. The noise will change as windows are opened or the cursor is moved across the screen or whatever. Cables are all shielded although the output is still unbalanced. I’ll continue to muck around with it this weekend.
tom -
I have this same problem on my Dual 1.42 G4. If you use the mouse or click buttons you hear interference from the Mac. Never could solve this.
Warren
Warren Eig
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