A large part of the success of the SSL could be attributed to the mix automation.
Originally this was a VCA based system however in 1991 SSL introduced “Ultimation”, their version of motorised fader automation.
Ultimation gives the possibility of working in a clean non VCA path (motors on) or a VCA path (motors off). The system was designed to allow retro-fitting and so can be found on consoles older than 1991.
As with all things SSL, opinions vary. Ultimation offers a non VCA (lower distortion) way of working and looks impressive and can be more expensive to maintain.