Good 6550/KT88 tubes

Hey folks,
Can someone tell me what the sonic differences are between the Svetlana KT88 and 6550c tubes are? Also I heard that the Tesla KT88 tube is one of the best production KT88's out there? Any comment? I am looking to tube my Rogue Magnum 120's and could use the help. Any tube suggestions would be appreciated.
Thanks guys
you can change the sound quality by replacing the 12AX7 input tube. I used Mullard CV4004 in my 120s and the sound was warmer and fuller in the midrange though a little less extended.

hope this helps

The Svetlana KT88s will give you a more classic tube warm, smooth, liquid sound than the 6550s.
The three KT-88 choices are -- Svetlana, Tesla, and Electroharmonix. Svetlana is warm, full and nice. Tesla is also nice, a little brighter on top, little less warm. The Electroharmonix is too new and not much is written about their sound except a few people's comments how they like them. I have some for sale I bought and didn't use cause I switched to a non-KT-88 amp. The EH is being used as stock in the Magnum version of your Rogue 120, however.
Some guy has an ad for EH 6550's and says they are the identical tube to the EH KT88. NOT!
They may look the same, but they are not the same. Although I really didn't get a chance to really listen to the EH KT-88, I did briefly compare it to the EH 6550 and it was definitely better. I, too, did note the how similar they looked, but they are not the same.
If you're sufficiently committed, then get some original Tungsol 6550s. They're noticably superior to the EHs that came with my 88 Magnum. Am using them in conjunction with mullard cv4003/4s.
If you are REALLY commited, get some 'black plate' GEC KT88s from the 1960s.
Since TungSol 6550's are about $600-$900 quad, and GEC's $1200-$2000 quad, Svetlana's KT88's are about the best I have heard, for reliability, and sonics. The ones with the wing C logo, are the ones made by the factory in St. Peterburg. The others labelled Svetlana are made by Reflektor, which makes the tubes sold under the Sovtek banner.If you have the bucks, the vintage tubes, do sound better, and tend to last 3-5 times as long.
I would look at KT90s too has alternative.
See and for info and prices.

I'm in the same boat as you, with a new-to-me c-j Premier Eleven-A.
I like the Ei KT90s.
How about SED =C= KT88? It's said that this tube is manufactured in the same factory with Svetlana in St. Petersburg. How SED KT88 compare to Svetlana?