Marantz 8B, best tubes to use ??

How about the original tube for this amp? Mullard EL 34 XF1 or XF2. Problem is cost, both tend to be very expensive if new in box.

Like Ed, i had Sovtek's in my Marantz. Tried a few other tubes in it, but that's what i came back to. I sold the amp a while back though, so i can no longer make comparisons in that specific circuit. Sean
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For the pentodes the EL34 metal base have the best resolution and cleanest sound. There is little difference between the 6CA7 big bottle (Philips ECG or Sylvania only).
BTW: Siemens never produced any EL34.
You might also try to play with the 6CG7 and the 6BH6.
I use Philips labelled 6CG7 (D-Getter) from the 50's.
I'm currently try to find Philips E90F (=6BH6), mesh plates

try the "winged c" svetlana tubes (or SED as i think they are now labled in the states) a very good all round tube that is pretty cheap and beats the sovteks into the dust!

I no longer have a Marantz 8b so I cannot attest to the preformance of the current offerings in the stock 8b. I would concurr with Albertporter on the voice of the Mullard fx-2 though as the original model 8 and 8b were voiced with that tube. The original American nos GE, sylvania and phillips big bottle 6sca7's were rather warm and fuzzy when directly compared to the mullards in the 8b.That said: Even the esteemed fx-2 paled in comparison to the Genelex KT-77 [a beam power tube] that was supplied as the stock tube in the model 9 monos and offered as a more expensive option for the 8b. Although they are obsenely expensive today and typically sell for 3 times the cost of nos mullard fx-1's or fx-2's, they are far and away the best output tube for the 8b.