I took a look at the manual for the model 38 preamp (not for the 38S, which I couldn’t find; the manual for the 38 is available at hifiengine.com if one is registered there).
I realize that you said the manual was of no help, but assuming the manual for the 38S is similar to that of the 38 it seems likely to me that the key to the solution is either in the section of the manual entitled "Assigning Record Outputs," starting on page 19, or in the section entitled "The Record Select Mode," starting on page 26.
Hope that helps. Regards,
-- Al
I realize that you said the manual was of no help, but assuming the manual for the 38S is similar to that of the 38 it seems likely to me that the key to the solution is either in the section of the manual entitled "Assigning Record Outputs," starting on page 19, or in the section entitled "The Record Select Mode," starting on page 26.
Hope that helps. Regards,
-- Al