Best modern 6550 tube for ARC per-amp

@mmbl622 
I find in interesting how so many can so passionately claim there is no way a voltage regulator tube in the PS can play a part in SQ.  Well I was a skeptic until yesterday.  I recently got an ARC REF 5SE and wasn't as impressed as I expected moving from the LS27.  My 6550 had about 1800 hours and I swapped a new EH 6550 and was blown away.  I took the time to swap the old one back and then to the new one again and there was no question.  Everything opened up with such better detail.  All the instruments and voices popped and were so precise.  I had read in some thread here a while ago how important these 6550s are in ARC preamps.  I am going to stock up on the Sovtek as that is what ARC ships their units with so that's good enough for me.  

i have….let me look ( press the button ) 5,188 hours, blissful hours on my Ref 5se. In this preamp, this circuit this tube matters. As do tracking the hours on it. ARC recommissioned 2k hours on that tube. I have about that on a NOS New Jersey Tung Sol from the 60’s. It transformed the bass and mid bass in my system even vs a new direct from ARC tube. Andy at Vintage Tube Services. i trust him. 

There have been man anecdotal posts over the years regarding tube rolling in ARC Preamp’s, and the 6550 in their power supply definitely changes the sound....and I can “parrot“....ah I mean 
confirm, (😊) , this in my observation as well in my REF 6 SE......
Cheers....

Audible differences can cleanly  be heard with any old Jimmy Buffet song, fellow Parrotheads…

that 6550 is not in the signal path, but I bet you will still hear a small difference. 

I would be inclined to try a PSVANE KT88 gray glass tube...