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
Roland SP 606 sampler
Roland MC-909
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.