Good 6550/KT88 tubes

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

Phil

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.