Carvin sx200 schem link
carvin sx300 3 channel amp schem link
carvin sx300 rackmkount preamp schem link:
this may be the one you want. I owned this one back in the 90's when I lugged a rack everywhere. It was a good solid state preamp. It sounded really nice into a Marshall 50 watt power amp.
Carvin amp schem page link
Carvin cuts corners on transformers and hardware and it makes their amps sound less dynamic than high voltage tube amps should.