In any single-ended product the quality of the regulator is certainly quite audible! And while the signal does not go through it, the regulator has to have good linearity just like any power amplifier- and that is exactly what it is. So you want to use a good tube. JJ makes a blue glass variety that is quite nice and not crazy money, also reliable.
Best modern 6550 tube for ARC per-amp
There are a lot of modern 6550 tube in the market such as Reissue Tung-Sol 6550, GE-6550A (Green letter), Svetlana 6550, Russia Gold Lion 6550/KT88........etc. What is the best modern 6550 tube for ARC per-amp in your opinion? (PS: GE 6550A is not newly made but still a lot in the market).
I used to own a NOS black plate 3 holes Tung-Sol 6550 but which has leak and now I’m using the stock Svetlana 6550. I want to buy a nice sound 6550 for my ARC Ref 6 and my stock Svetlana 6550 will be used as spare. Will not consider NOS black -plate Tung-Sol again because of pricy and not sure the condition.