See below, which I posted in another related thread:
I don't know the Digi003 much at all, but I do use a Digi002 and an ADA8000, so here's how it works on my rig. First- sure enough, the ADA8000 isn't a mixer, and there are no inserts. It isn't a mic
preamp either, exactly. It's an 8-channel analog to digital and digital to analog converter that does have built in preamps. The only way to get anything to come out of the analog outputs is to have a digital input. As suggested in passing above, you can run an optical (Toslink) cable from the ADAT out of the Behringer to the ADAT input on the Behringer, and Hola! you will get analog output! Upside- It works. Downside- you have to run the signal through a cheap A-D/D-A converter *twice*. So- if I was using 2 ADA8000's with my rig, I'd run one via Toslink cable into the ADAT input on the Digi002, and the other one into analog inputs 1-8, except--- I would use the Digi's preamps on channels 1-4, because even they are a little better than the Behringer, and it shortens the signal chain. I only use the one into the ADAT input, and outboard preamps on 4-8. If the 003 has 2 ADAT inputs, just use those. That's what I don't know. How many ADAT inputs and how many channels does the 003 support? Hoping this helps.
So- the answer is basically no. You can get 8 channels into the ADAT input, and if you jump the second ADA8000 from ADAT out to ADAT in, you can get preamps for four more channels (5-8). Channels 1-4 already have preamps. This leaves you 2 channels by S/PDIF, for a total of 18. For any more inputs, you have to create a submix, and you can't mix them as separate channels later. This is usually done with a mixer, and more often with drums than anything else. The ADA8000 is not a mixer, and it doesn't do that.