Need help with tube selections

Just recently purchased a pair of McIntosh MC-75's. These are my first venture into tube products. I know you can use either KT-88's or 6550's. But which one of these are the best? And, which brand should I buy? Any help would be appreciated. Thanks
On my Sonic Frontiers Power 2 I took out the 6550's & replaced with KT 88's. The improvement was dramatic. The Kt 88's were Tesla & then I tried Svetlana's. The Svetlana's are, in my system, a bit more musical than the Tesla's. But not really significantly. The only way to tell is to give them a try. If you don't like them sell them on this web site.
Good Luck.
We have tried the KT 88's with numerous amps that come with the 6550's and we have always considered the KT 88's to be superior from top to bottom. We have also tried the KT 90's and have still found the KT 88's to be overall the superior tube.

You are now experiencing one of the advantages of tube equipment and that is that you can change the sound of your system by changing the tubes. Changing the input tubes can also tune the sound of the system although usually not as much.

We have tried the various brands on the market and like the KT 88 STR's by Ruby Tube.

Good luck and have fun!
The options that are avaliable to you are either the 6550, or the KT-88. Getting Old Genelex/MO Valve KT-88s will be QUITE expensive, and they will probably be used. Sylvania 6550s could be had for some folding money, otherwise you are looking at mostly Chinese tubes. There is still some black art to making tubes, so eventhough some chinese KT-88s are 6550s in a bigger bottle, there is a difference. As to the driver tubes in this amp, stick with what the lettering says, or the industrial equiv.
I would strongly urge you to stay away from the KT-90, it is an unfinished product with a lot of hysteresis.
Happy listening.
The best sounding tubes for your MC-75 will be the GEC Goldlion KT-88 tubes. They are expensive both they worth it.
A set of four will last your life time!!!!
call andy at vintage tube svcs (no i do not work for him). he has always given me good advice and tubes. and if i do not like them....he will take them back! i am buying tunsol 6550s from him for my rogue 120s. i have heard electro harmonix has a good kt88 (per mark obrien at rogue). rogue also sells kt88 selects with thier name on them that go in their magnum up grades. i would buck up and go nos tubes. the difference in my equipment (pre-phono pre- amps; tuner etc) have been big. i am sure there are other good nos tube dealers out their too.

good luck
sovtec kt88 end of story. if you like i will try to locate some.
ask for Andy
I have a rogue 88 and the best tube I have tried is the electro-harmonix 6550EH. I have tried kt88 kt90 & svetlana 6550b & 6550a. The electro-harmonix 6550EH is nothing short of stunning...thay can be purchased at the
I dunno.... I tried Svetlana KT-88's and the Svet 6550's in my CJ Premier 11a. Still undecided. The 6550's still sound very good to me and I do not hear the HUGE benefit of KT-88's that others describe.