I've already configured it that way.
The lower card is the master.
But the analog inputs 1-8 are those of the slave (upper) card..I'm not really sure if mac os really "sees the lower cards first" since the port numbering is the other way around.
My main problem is that I get no output master audio from either card.

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The instructions from M-AUDIO are as follows :
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Q: How do I configure Multiple Delta Series cards to run together?
A:
- You will need a 75 Ohm S/PDIF COAX Digital Audio cable for the external synchronization.
- Define one of the Delta Series cards as the card running in Word Clock Master mode. Best would be to choose the card that doesn't share an Interrupt (IRQ) with any other device (check the Device Manager for IRQ sharing). When using a Macintosh Computer running MacOS 9, choose the card in the lowest PCI slot as the Word Clock Master. (Delta Multi-card setups are not yet supported in MacOS X).
- Set the selected Word Clock Master card to "Internal Xtal" in the Delta Control Panel's "Hardware Settings" tab. In the Patchbay/Router tab, set this card to "Monitor Mixer" for the "HW Out S/PDIF". Activate "Single and in sync".
- Connect the digital output of this card with the digital input of the second Delta Series card. Set the Master Clock of the second card to S/PDIF ("Hardware Settings" in the Delta Control Panel). Activate Multicard Mode.
- If you are using three Delta Series cards, the second card should also be set to "HW Out S/PDIF" for the "Monitor Mixer" in the Patchbay/Router tab.
Make the same settings for Delta card #3 and # 4.
If Delta Audiophile 192 card is part of your setup, make sure to use this card as the last device in the synchronization chain.
The Operating Systems Windows 2000/XP support "KernelSync" and do not necessarily need the external connection using S/PDIF. Delta 44 can only be stacked in these Operating Systems, since this card does not have a S/PDIF connector. For this type of Operation, all cards have to be set to "Multiple Card Sync".
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One other thing is that this step:
" In the Patchbay/Router tab, set this card to "Monitor Mixer" for the "HW Out S/PDIF". Activate "Single and in sync". "
I can't find any " single and sync " option on the Delta Control Panel.
I've only set to the "Monitor Mixer" for the "HW Out S/PDIF" on the master card.
I suspect that the lack of Monitor OUT audio has something to do with this..
I'm using Ableton Live btw..
My plan is to have some outboard synths patched to 16 analog inputs and be able to record them simultaneously while monitoring the master stereo mix thru a pair of Delta outputs connected to my monitors.
Should the Master Out output from the the slave card since I'm setting monitor on the master to S/PDIF ?
I'm sorry If I don't make any sense but this is all really confusing to me..
I'm used to RMEs excellent TotalMix. The Delta Control Panel is really badly implemented IMO..
EDIT :I eventually got audio output from outputs 11/12 (on the master card) so those would correspond to 1/2 outs on the first card (which is the slave).
I'd really like a way to get the numbering right while keeping the low PCI card the master as per M-AUDIOs' instuctions.
Anyway, I'll try some things and report back on how things work..