The Plus with a good pair of gain tubes sounds great, far better then the SS buffer stage alone. I suppose the latter is comparable to the S (less the SS gain). Am I correct?No. Freya S runs a "Nexus" gain stage, while Freya + runs a JFET buffer:
From Schiit:
"The Freya+’s "JFET buffer" uses a gain-of-1 compound-pair JFET differential amplifier, coupled with an equalized-transconductance BJT output stage. So it converts single-ended to balanced, so now you have another option if you want to convert an SE source without using tubes."
Here is a great comparison of Freya S and Freya + by trusted ears: https://www.superbestaudiofriends.org/index.php?threads/schiit-freya-and-s-impressions-stream-of-con...