Here is a well writtten review with pic of the inside. Very Impressive.
https://pt.audio/2017/07/30/mcintosh-mp1100-phono-preamplifier-review/
Here is a quote in the comment section to the article regarding tubes:
My favorite tubes for this phono is the Mullard Long Plate MC1s square getter, truly “airy”, organic and musical. The ones in the pictures were Telefunken’s, they were less glittery than the stock tubes, and I also find them to be more “organic”.