ahh, yeh sorry..a bit vague. here's where im at....

I've got 3 ff 800's, want to use PT9. PT will only accept 32 ins and outs.
When Im in audio/midi setup (OSX10.6.6) i can select either of the 3 ffaces to use as the protools aggregrate i/o. giving 28 in and out of one unit only. PT is happy with this.
At present if i add all 3 units into the protools aggregrate i/o it sees 84 ins and out, and crashes every time. I think its because, and after talking with a tech from Avid who agrees,  PT9 only accepts 32 i/o.

However, what i would like to be able to do is use the 8 analogue outs of each unit, eg 1-8 ff1, 1-8 ff2, 1-8 ff3 - giving me 24ch into the desk at 192k. Rather than having to route out of the first unit into the second by adat, and also to the third unit by adat...giving a max of 12ch at 192k.

Is there a way that i can 'switch off' or hide the adats/spdif in audio/midi setup or some other software so that the PT aggregrate i/o will only see 24 in and out.
Does this make any sense..??

this might be a tricky situation...but thanks for your help.
s.

Unfortunately the number of audio channels in Core Audio stays the same, even after a reboot. This feature takes load from the FW bus, but can not be used to select channels with Aggregate devices.

Your current way to do it is the best, as more than one FW unit is calling for trouble anyway. But when working at 192 kHz I see no solution, sorry.