Mbox and mbox pro - linking them together

[kvp]

Hello. This might be a stupid question, but here goes: I have the mbox with 2 inputs. Is it possible to use the mbox pro with 4 inputs and connect the two using s/pdif and that way get 6 inputs?

[serio]

if both Mbox and mbox pro drivers can live on the same computer happily, then you should be able to do this. Since the mbox doesnt have a stand alone mode you'll need to have it connected to the computer via usb as well as have it's SPDIF outs connected to the Pro's SPDIF ins. in the Mbox control panel, click the SPDIF out tab. Turn your analog channels 1 and 2 up to unity and now signal will pass freely through the digital outs(you still control gain via the front mbox knobs). if its mono signals you want to feed, then unlink the channels and pan them center. When pro tools is running, you'll want to make sure that the Mbox Pro is the selected hardware device and you'll want to be clocked via SPDIF instead of internally.
Alternatively, you could try making an aggregate device but that's a whole other story and set of instructions.