Tape.
Transformer based pre with steel core or 50/50 steel core transformers.
The transformers have to use shitty quality steel cores though, not that brand new state of the art stuff. Think WWII steel.
Cassette deck with 3 heads so you can realign it in the DAW.
Mic your monitors and record the playback of your synths that way.
Run your synths thru a reamp box into a tube guitar amp and mic it with whatever gritty ass chain you want.
If you can't get a Gates Sta Level, try the Solid States Man. Has a shit ton of iron in it and sounds just like it, dope on drums, guitars, bass as well. The AGC is the one I have and I can use it on most anything and find a pleasing result when I want dirt!
Peace
Illumination