Question for tube aficionados

I think lowrider57 may be incorrect. The Mullards could be new production or old. The Yugoslavia 12AU 7's are definitely old stock. They haven't been inproduction for 20+ years. When this unit was first produced I don't think  new production Mullards were available - my guess is that they are more probably old stock and I think that the NOS and new production do not have the same tonal qualities. 

I'm not familar with your pre-amp but I suspect that the V1 and V2 positions are likely the positions most affected by tube changes. If that is so, and if I wanted to play with tubes changes, I would start there keeping in mind that different brands have different tonal qualities and it helps a lot in selecting tubes you want to try to have some 'tonal' goal and try tubes that have a similar tonal signature.

rvpiano, Check with CJ, but FWIW I can't think of a single reason why tube selection in the line stage would affect the performance of the tubes in the phono stage, except for the obvious one is that the phono stage signal passes thru the line stage therefor any tonal changes brought about by the line stage tubes will be reflected in the sound from the phono (or any other) source.