No money for that right now, and I'd rather not think about it.

I still think there may be a separate, minor difference, beyond just the muxed format of that optical out. It wouldn't affect me, if I were running on an external clock, only if I were sending clock to that AI-3 and trying to bring it's eight audio signals back to the control room (or listen to them anywhere).
My guess was that maybe the 2408's clock was right on the edge of whatever "level" of light, or clarity of the wave transitions could be tolerated by the Alesis. Like I said, the 2408 output seemed to be fine to some other stuff here, but the Alesis had no problem with the other stuff's clocks, so it would sort of point to the 2408. Even if the Alesis was overly picky about such things, the 2408's output must have been just the slightest bit more dirty or jittery than the other stuff. (dunno

Take Care,
George