my fears were unfounded - the machine booted up to a perfectly clean sound. i am finally confident that the machine is fixed.

all i've done since the last reboot is reinstall the operating system firewire drivers. i didn't even swap them, i just disabled them and rebooted, which forced me to also reinstall the mixer drivers. that seems to be the only thing i needed to do (besides locking the drivers).

it might seem like something i should have never overlooked; that it should have been one of the first trouble-shooting steps. but, i've got all my driver installs sequenced in an install script, so when i reinstall the machine i'm dealing with fresh, updated driver installs for every device in the machine. it's reasonable that it never crossed my mind to reinstall drivers for a system device immediately on a clean boot.

but, there's some evidence that it may actually be the registry wipe i run post-install.

before i run the script, i can uninstall the firewire drivers through device manager. after i run the script, it tells me i can't uninstall them because they're locked by a parent driver required for start-up. that sounds wrong - as though i've crossed something during the registry wipe. what i have to do, instead, is disable them first and then uninstall them.

what i've got back now is the "sound stage" - i can hear the reverb in proper stereo and all the effects have their decay back. it's the reversal of that compressed sound that i was associating with bad conversion. so, i have to conclude that the firewire port was somehow truncating the stream. when i put it into the context of the files always nulling when output to disc, it does, in hindsight, make sense to tie the issue entirely to the firewire streaming, as the issue was purely playback related.

that was a long, difficult process for what in the end was a triviality. but, i really think it's figured out now, and i should be able to get some listening in this week and back to mixing next week.