I know that at the Rock and Roll Hall of Fame (see:http://www.rockhall.com/) they have both Alan Lomax's original recording equipment and the original Sun Records Recording Studio on exhibit. They might be a good source to address this question.
We who attended the ARSC Conference and went on the field trip to the Rock Hall saw those exhibits, which were quite fascinating. A recommendation concerning this is a new book called "Temples of Sound," which goes into detail in exploring legendary recording studios in the post-WWII period; independent studios like Sun, Chess, Stax as well as RCA's Studio B in Nashville, the Capitol Tower, Jerry Wexler's Atlantic machine, etc. The book is published by Chronicle. It started out as a photo book of in-studio shots (which are fascinating in and amongst themselves), but was expanded into a virtual oral history of how each studio got the sounds they did.