Noise from PTHD system

[stuarta]

I don't know if anyone has come across this or has a cure so here goes.

I get a high Pitched noise through all my speakers when my Dual MP 1.25 Ghz Mac with a PTHD III system installed is turned on.

Sometimes the noise has an almost rhythmic quality to it ad sometimes it is simply not there. Somehow the noise is even getting to the speakers even when I have the outputs turned off at a Multimax.

The only way I can guarantee to eliminate this noise is to turn off the computer.

I have tried all the usual Isolations and Ground fault test to try and locate the source, but it always ends up at the computer itself.

The entire studio runns from one (Big) Power outlet through severla line conditioners etc. The only way the computer system is different from the rest of the system is that it is run through a big APC UPS.

I have tried bypassing the UPS to see if that was the problem but no joy.

If anyone has any ideas as to the cause of this I would appreciate hearing what you did to cure it.

I did have something similar to this a year or so ago and found that by isolating the MIDI Interface Chassis from the Racks and moving the Speaker Controller to a different rack cured the problem.

[clarpark]

http://duc.digidesign.com/showflat.p...=5&o=7&fpart=1

there are more threads too. Do a search...welcome to the party.

[JGuth]

Is the computer's audio output (mini jack) at all connected to your mixer or patch bay? Try removing that if it is. Same if there are any other computers connected.
Is the noise still there if the HD audio cables are disconnected? etc etc. Eliminate things one at a time untill you find the source.

[JGuth]

Also check for audio cables too close to the computer or video monitor cables etc.

[clarpark]

jguth, why you are sending him on a wild goose hunt? This is a real issue from apple and there are mountains of information about the real source of the problem, ie the g5's powersupply.

[stuarta]

Thanks Clarpark, that does sound like a possibility, any idea if it is heat related?

I have tried ALL THE BASIC Stuff Loose cables, Audio from Computer ed back in PT system. Clock Sync, Bad Grounds Etc, I know you all mean well, but I am really looking for something here that is none of those things, very wierd and Intermittent although it lasted all day today.

About the only possibility I can think of that brought it on, was installing Rewire as I definitely did not have it before that but removing Rewire now does not affect it.

Sometimes you got to hate this game

[clarpark]

have you put a ground lift on the g5? if that doesn't help, apple is replacing power supplies as a fix...

[RobMacki]

This is interesting.
I'm getting ready to put in an isolated ground for my studio circuits.
I had no noise until I installed my HD2 w/192 I/O.
I'm on a PB G4Ti / Magma CB4 whenever the computer and Magma are on I get high pitch buzzzz.
Before that all was quiet.
No G5 issue here, but I hope isolaed ground will help.