G5 noise when recording Midi to audio

[fuzzles]

I've just started having a problem with built-in noise when recording my midi tracks to audio - never a problem until now. I have a 2G Dual processor G5 and previously only had noise when I had the audio out on the G5 going out to 2 other channels on the mixing board. Pulling that cable out used to get rid of any low-level noise. Now it's happening with nothing plugged into the G5's audio out and I see it on input in Pro Tools and showing up on the 192's meters. Anyone have any ideas of likely culprits to check? It's now appearing on every track I convert from midi to audio.

Thanks in advance for any ideas!

PT 6.9
OS 10.3.8
HD Accel 2
192 I/O
Digi MIDI

[crizdee]

Hi,

This sounds like you have some signal coming in on the inputs of your interface, try to disable the inputs from your hardware setup and try to isolate which inputs are causing this!? recording midi to audio!! is this internal or external midi instruments?

Where do your interface inputs come from? are they routd from a mixing desk or a patchbay etc, if yes then try unplugging them from that end etc.

Also check your digital inputs in your hardware setup, make sure they are disabled if you are not using them.

Chris

[DigiTechSupt]

Also, make sure you don't have some kind of grounding issue. By plugging and unplugging cables, you may be able to determine the source of the noise. There are several options for reducing ground loops like plugging all hardware into the same circuit, using balanced cables where possible, etc.

[fuzzles]

Thanks, Chris & Digi for your replies. I found the culprit - by disabling "allow nap" in the Processor department of System Preferences, the substantial noise disappeared. I had tried all sorts of troubleshooting with the mixer, ground alternatives, Energy Saver settings that change the amount of fan noise, etc. but disabling "nap" did the trick right away. Apparently, Apple doesn't recommend doing that, but 'til there's another workaround or fix, I'd rather live without the G5-induced noise. Thanks again, guys!