For those with early SC2 compressors…. and there are hundreds of them still in service, the earliest ones had SSM2142 output chips, and at the time we had problems with reliability, a number of them went ‘pop’. Also, a number of users wanted an on-board make-up gain control, so I relaid the board and introduced an active output stage. This proved to be reliable. All SC2s after that had the later output stage.
The SC3 was a short-lived version with an experimental M/S matrix and digital in/out. This swiftly became the SC4 which was very successful. It had the M/S matrix and a very good digital section.
The very last SC2s that we made also had the M/S matrix, the advantage being a rock-steady image even under high compression.
TFPRO compressors, the P38 and P38EX, both have a more sophisticated M/S matrix with variable width. They also use a different type of optical cell with a faster response; the different compression characteristics are produced with different ‘shape’ attack and release characteristics.