My Fairchild compressor is a hybrid.  The original used a high voltage tube amp with a step down transformer to drive the side chain diode bridge. I used a high current solid state amp with a 40v rail and a 1:2 step up transformer.  I also used an active output with high impedance input allowing the use of only 1 - 6386 tube [a considerable savings at $120/tube.  The time constants are true to the original but with attack and release controls.