We have an etcexpress 250 and run all conventional lights on channels 1-96. I want to add some dmx through 2nd universe. Whould my first address be maybe 100? Or would it be 513?
Depends on what your output configuration is set to. I have an expression 3 and my setup is default. I would start with that page and patch accordingly. I attached what mine looks like as a reference. To get there it's Setup > 2 > Enter.
I don't know what the default is for the 250 but you will need a channel per DMXchannel to control everything.
So on my 2nd port the start channel is 513 but the dmxaddress would be 1 on whatever device you addressing.
To get the most out you channels you will have to patch whatever your starting dimmer number into CH 97.
When I ran the 250 in the last space I was in I adjusted the outputs to Port 1 @ 1 and Port 2 @ 100 so everything was a whole number. Again the starting address for your dmx would still start at 1 just controlled by Ch 100 if you are 1 to 1. To get the max it would be CH 97 DIM 100 so on and so forth.
This is a link to the rough hook up hope it helps.