JC mean John Curl, the designer. This amplifier was the first version of the ML2.
Rolv-Karsten R¿nningstad says:
Regarding JC-3 and ML-2 power amplifiers:
I do not think the JC-3 was ever released under that name. My personal guess is that John Curl left Levinson before the JC-3 project was finished. The chief engineer Tom Colangelo is mentioned as designer of the ML-2 I think, and I guess he took over the project and finished it, and the amplifier was Christened the ML-2.
Among other things changed on the ML-2 there is an active J505 current source for the input JFET differential stage. There is a balanced input, and the minus-input is buffered with a simple n-channel/p-channel JFET pair. Further the second stage is a cascode connection. The JC-3 shows four output transistors: The ML-2 has four 2N5884 and four 2N5886. The ML-2 also has an active power supply. The heat sinks closest to the front on each side carries two 2N5884 and two 2N5886 respectively.
