freestompboxes.org

Carvin sx200 schem link
http://www.carvinservice.com/crg/schema ... rt%201.pdf

carvin sx300 3 channel amp schem link
http://www.carvinservice.com/crg/schema ... mpRevE.pdf

carvin sx300 rackmkount preamp schem link:
http://www.carvinservice.com/crg/schema ... 300R-1.pdf
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
http://www.carvinservice.com/crg/schematic_finder.php

Carvin cuts corners on transformers and hardware and it makes their amps sound less dynamic than high voltage tube amps should.

S3.A on A.3B on the sx200 schematic is neat. Adds a filter to the negative feedback loop, doesn't it? But only sends part of the signal through it. R56 and R57 appear to form a voltage divider.