[Musica Amantem]

You know, I've used 6550's in my KT-88 strapped as a Triode SEP, along with the cited preamp, and I was not convinced. It did change the overall sound flavor but not as an improvement. Good KT-88's with the right rectifier (be it 5Z4 or the 284 mesh plate, depending on the tracklisting) can be just the thing in this setup. In my amp KT-88's have spark, something that is not that common in tubes, and at the same time present a very balanced sound over the essential frequency range. Midrange in general (female vocals, for example, or cellos, violas, etc.) sound quite natural and with more or less the right timbre depending on the recording quality. I start to miss the KT-88's when I swich to 6550's, which make for a nice change of pace but not the best ouput tube in my setup. At least, that is my recollection of it. Need to listen to them once again and compare ... Nice! No doubt YMMV, this is just my personal opinion on them.