Tube Preamp: How many tubes does it take to .................

The amount of tubes means very little ,you truly only need2

somecj preampsonly 1 tube they split 1/2  of each side

the transformers ,chokes and powersupplies make they most difference 

quality counts ,look atVacuum tube guru Radu Tarta  all highendLundahltransformers or chokes ,or Yamamoto, or Monolith

snd he don’t use coupling caps ,he believes in Highend transformer coupled 

its much more $$ but excellent signal isolation and purity .

capacitor coupled too cap an be very good but high quality parts count 

look atLinear Tube Audio  Micro Zoe  very nice tube preamp with several tube choices .

VTL 7.5 linestage only has two tubes. Nice not to be in the tube rat race

I think about the future when it comes to tube replacement time and the cost involved. Since I'm not a man of means as some folks here clearly are, I shy away from equipment with more than 2-3 tubes. 

I put several tubes in my Pass XA-25...they just roll around in there but it does make me feel better.

It also depends on when it was made. If it was in the 1950s or 60s them of course more tubes because that’s the technology of the day. My McIntosh Mx110z has 17 tubes but it’s a pre, phono and tuner and was made circa 1960. My more recent C2300 has 6, 2 for MM phono, 2 for MC phono and 2 for Aux. Same for amps where my MC30s have tube rectifiers instead of ss, They have one more tube per channel than my MC240. Technology.