I designed the SC3 in March 1997, it’s actually identical to the SC2.2 in electronics except that it was designed to interface with the digital equipment of the time; some engineers wanted to use the digital in and out facility that it has. The digital circuitry was designed by my old friend Steve Dove using the best available ‘crystal’ chipset of the time. The SC3 has transformer inputs working in ‘current mode’ as my modern circuits do. It also has a particularly ‘hefty’ output stage, so it can operate perfectly in any environment.
All these early optical compressors have tiny variations in the way they sound and I agree that the SC3 does have a happy gain structure that makes it impossible to sound bad!
There were only about 30 of the SC3 made so they are quite rare….. hang on to it! 
