Hi everyone, my name is Matt from Canberra, Australia.

I realize this might have been covered in other posts, I've done a search and have seen a lot of posts from people with similar issues, but across all sorts of different systems (PC / Mac), so I thought I'd post mine up and see if anyone had any ideas.

We use a Fire Face 400 in a studio environment with Mac Pro's here at work for sound design, mixing for film / TV etc etc, and have noticed a very audible high pitched whine / squeal / buzz while it is in use. Our setup is as follows:

Mac Pro 3,1
8 GB 800 MHz DDR2 FB-DIMM
OSX 10.5.8
FF400
Sony DMX R-100 mixer

We have tried running the FF400 off an external power source as well as the firewire bus on its own, with similar problems. Even when the Mac Pro is switched off, the firewire bus still supplies power to the FF400, and you can clearly hear the whine and interference. We have tried using different firewire cables, differenct tie lines between the studio and machines room, all with no effect.

I have swapped out the FF400 with a MOTU unit we had lying around, which comes up completely silent, so that pretty well eliminates the possibility of it being RF interference with cabling etc ...

I have also hooked up this FF 400 to a Macbook Pro laptop, then to our DMX R100, and have had no such whine / buzz issues, which leads me to the conclusion that it is something to do with the way our Mac Pro interacts with the FF400.

I have read that there is an update for OSX 10.6 which may be able to help remedy the problem, however we are stuck on OSX 10.5 and are unable to upgrade to 10.6 because of our XSAN fibre network storage system here.

Anyone have any ideas ? I have a sneaking suspicion it's to do with power supply from the Mac Pro's firewire bus, but would love to hear what anyone else thinks ... And if you've got a solution, that'd be great !

Cheers,
Matt