Best modern 6550 tube for ARC per-amp

That's another thing I like about JJ, besides the sound quality, which is very near the top, you get a price that is very near the bottom.   
Almost all Tubestore.com tubes come with a 90 day warranty. The warranty on their Preferred Series is 6 months. I have never in nearly 30 years had a tube fail between 90 days and a year. In fact, I don't ever recall a tube failing in under 2 years, except for a couple Preferred Series tubes that blew within one month! The only tubes I would strongly advise against, had the best warranty. The extra you pay would seem to be for the warranty you will use. Hard to imagine anyone seeing the way mine failed would consider that worth the risk.   

All the many others, if they make it past the standard 90 they probably will go a good long time. Paying extra for a one year warranty in other words is a good profit center.

just a note to the op - who is seeking info here

don’t mind us tired old hacks here on this board doing a little keyboard jousting in the late night... some joust better than others when scotch or burgundy or ........ is involved  :)

what you will hopefully take away substantively from here is that given the ref 6 uses the 6550 in the ps voltage regulator function (and not a primary signal amplification function) replacing that tube for hopes of better SQ is a ’maybe’ proposition - certainly more of a 'maybe' than upgrading the tubes actually handling the music signal (even though that can’t be done on your unit given the 4x 6h30p’s...)

but yes, in practicality, it all matters (more or less is the main issue at hand) and it is just one tube, so it’s hard to waste too much money chasing a ’maybe’ in this case - i would still suggest checking in with greg at arc to get his take/advice - they made the amp, their input is valuable

my post below was only sarcastically referring to your ref 6 as a p-o-s -- hopefully you don’t take that seriously, we all know it is a lovely piece, one of the very best - i have the ref 3, love it, can only imagine how sweet the ref 6 sounds

cheers and good luck

I run various KT88 and 6550's in my ARC Anniversary Reference preamp along with Herbies tube dampers in all spots and can hear a difference between tube brands/dampers,  I also roll 6n6p tubes as a drop in sub for the 6h30p's for a very nice (and cost effective) upgrade...

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.