The IN-2 is not a preamp, but a power supply, or perhaps more properly, an Input Module. They are quite rare and feature the following:
- 18V power supply for Series instruments
- two stereo channels with four phone jack outputs each
- low impedance direct outs for each channel
- mode switch for selecting stereo, mono, channel A or channel B
As for what makes it special; it has more functionality than a DS-5R.