Kevin, of Upscale Audio. I come to you, THE TUBE GURU, with a question. I am using KT90(the OEM supplied tube) in a Jadis Orchestra Reference integrated amplifier, with great results. Eventually, I will obviously need to retube. I contacted Jadis questioning them with a list of tubes I'd consider in the amp in the future(EL34/E34L/6CA7/6550/KT88). They responded they recommended all of them, EXCEPT the KT88. This was due to poor aging/life. I have NEVER heard of, or had this experience with this tube. If anything, they were VERY robust(more so than an EL34). In my follow up with them, they maintained their position. Can you please give me your impressions of their response? I would not expect this tube to have unacceptable life in the same amp which fares great with EL34/6CA7. Instructions state to bias to bias EL34 or KT90 tubes to the same specs(other tube types as well, upon clarification). But, you have quantum levels higher more experience in these issues than me. I may go to a more warm, sweet, and classic tube sound in the future(EL34/E34L), but am happy now. As KT90s have gotten real expensive in the past year(NATO bombing, I always hear), I am thinking my standard replacement would be the KT88(and get a bit more warmth/sweetness to boot). I am not the biggest fan of the 6550 sound. Any comments would be GREATLY appreciated! Thank you for your consideration.
