What is Audio Researches best preamp period

I like the ARC Ref 2, the model prior to ARC's decision to go the specialty Russian tube route (that have no substitutes).

The Ref 2 uses eight 6922's in the main unit and 5AR4, 6L6GC, and 6922 in the power supply. A world class preamp by any standard.

The ability to run NOS tubes makes this the last ARC Ref that can be fully tuned up to match your equipment, room and personal taste.

Avguygeorge, correct, I am Aesthetix Callisto and Io but was trying to give an ARC opinion based on some I have owned (SP10 SP11 and Ref 2 Mk2).

The new Russian tubes I am referring to are replacements for the earlier 6922 but are not interchangeable. Anyone looking for ARC that has NOS equivalent just check to see if it has the line up I listed:

The Ref 2 uses eight 6922's in the main unit and 5AR4, 6L6GC, and 6922 in the power supply.

I would normally do a web search to clarify exact model numbers but I board a plane for Denver AudioFest very shortly.