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.


mmbl622
Anybody who have experience to compare the sound quality of these tubes:

Re-issue Tung-Sol 6550 vs GE-6550A 
Svetlana 6550 vs GE-6550A

Someone offer me a 2nd hand green words version GE 6550A which is slightly use (asking the seller how many hours is use) at US$78.   Not sure how's the sound quality.

Another concern is not sure how's the condition of this tube because this is a used tube. Although the seller said it is only slightly use , I don't know how many hours it has been used. And I don't have any tester to test it. 


So, now one of your proposed strategies is to place a tube of questionable history, possibly fake, and with untold/undetermined hours of use in your $15,000 preamp? Right, makes perfect sense.
@tubegb

So, now one of your proposed strategies is to place a tube of questionable history, possibly fake, and with untold/undetermined hours of use in your $15,000 preamp?


lol...

well i guess we have all scratched the scab off of a healing booboo, make a bloody mess ... sometimes in spite of what is good for us... path to nirvana is often over some rough terrain in parts
Indeed, far from perfect. I could recount/regale endless stories of questionable moves/decisions made over the 40 years in this "hobby"...
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.