They are very good tubes but not perfect, perhaps the NOS Genelax KT88 are the best but the Sev kt88 have been in my system for about 1 month now and I very much enjoy them. They have a beautifull midrand and good overall balance. Greater clairity and sweetness than the Sev 6550C whicch are also very good, espically for the money. Right now I will keep my Sev kt88. John
