Spectasonics were a bit different as the designer went for greater linearity and fast response over other designers of that time. They touted the ability to pass square waves without messing up the waveforms. Modernize the discrete transistors and good things can happen.
Anyone needing any technical info on these should contact Ray Kimber at KimberKable. Ray has all the schematics, layouts and every book published on his huge library shelf in Ogden, Utah. He has 20 feet of Spectrasonics technical books. If there is anything else you need to know, the original designer is also located in Ogden as he's involved in avionics now. He has a Spectrasonics hanger at the Ogden airport.