This is a list of synths with digital outputs (S/PDIF) that should work on channe1 7/8 of the Roland MX-1 mixer. S/PDIF is an acronym for Sony/Philips Digital InterFace.
It's unusual that Roland chose to add a digital input to this mixer. Lot's of people complain about this saying its a wasted channel.
Possibly, the reason Roland did this was to allow addition of older digital synths with a S/PDIF output.
There are two types of SPDIF, coaxial using RCA plugs and optical which uses optical cables.
Roland uses the former.
You can of course just use a analog to digital converter if you just want to add an analog synth..
The MX1 needs to be set to the correct sample rate : 96, 48, 44.1 etc that matches the ADC you've purchased.
Access Virus TI **
Akai MPC 1000
actually lots of samplers have digital outs (like my Akai S3200
Yamaha A3000, A4000, and A5000 samplers
Yamaha Motif XF, ES
Proteus 2000 , 2500
Roland V-Synth GT.
CD player - eg Pioneer Nexus
Many home audio devices have SPDIF outs...CD/DVD players, MiniDiscs, HDTVs, etc
Waldorf Q Rack
Novation UltraNova
Novation X station
Roland XV5080
Korg Z1
Korg M3
E-mu Samplers ( e6400, e4XT)
E-mu XL-7 Command Station
Kurzweil K2600, Kurzweil K2661
Fantom X
Jupiter 80
Arturia Origin **
Oberheim OB12
Boss DR-880
Let me know if there are any mistakes or additions.
I'll add to this list as I find more of these old synths.