To stay on thread, I have really liked the Svetlana kt-88s but had some reliability problems running them in Audio Valve Challenger amps. Recently I came across some RAM-tested kt-88s that I now prefer.
Regarding kt-90s I find the assertion that they require very long burn-ins to be interesting. When I rolled them into various amps, usually replacing 6550s or kt-88s, I only let them burn in for 40-50 hours before determining that I did not like them. Who knew 400 was the ticket?
My current tube reference amp, the Jadis JA-100 uses 4 kt-90s per side and it sounded great right out of the box. It improved over the first 60-70 hours and then settled in. The improvement was noticeable but not dramatic. Jadis assures me that the tubes were new. They say that the kt-90 places special demands on the power transformer so they developed a proprietary hand wound unit specifically designed for the kt-90 tube. The amp self-biases and the tubes do not glow bright in the plates. I am not an expert in this area but I do trust Jadis to know a few things about tubes. Maybe it takes 400 hours for kt-90s to burn in a standard transformer?
Regarding kt-90s I find the assertion that they require very long burn-ins to be interesting. When I rolled them into various amps, usually replacing 6550s or kt-88s, I only let them burn in for 40-50 hours before determining that I did not like them. Who knew 400 was the ticket?
My current tube reference amp, the Jadis JA-100 uses 4 kt-90s per side and it sounded great right out of the box. It improved over the first 60-70 hours and then settled in. The improvement was noticeable but not dramatic. Jadis assures me that the tubes were new. They say that the kt-90 places special demands on the power transformer so they developed a proprietary hand wound unit specifically designed for the kt-90 tube. The amp self-biases and the tubes do not glow bright in the plates. I am not an expert in this area but I do trust Jadis to know a few things about tubes. Maybe it takes 400 hours for kt-90s to burn in a standard transformer?