Tell us about your KT150 experience

Soundermn, my experience echoes yours except I haven't sprung for the big ticket KT150s.. KT120s made my PrimaLuna amp sound transitory and I've been running the TS 7581As for many months....I like them even more than the GoldLion KT77s, which are outstanding but a little analytical for my taste.

I haven't replaced my KT150s yet.I bought them from VivaTubes.They have frequent sales so no need to pay full price.They ship quickly and no issues with any tubes.I always end up putting them back in after using some other KT88s or EL34s.They are by far my favorites.I am fortunate to be able to switch my Aric Audio amp to single ended, which I prefer.I love acoustic and electric blues so these tubes are perfect for retaining the sweet midrange while cranking out the power as needed.

I have a Prima Luna Dialogue Premium. I too run four 7581a power tubes and love them. Better bottom end & sweet midrange than el34b they replaced. Not as much power as gold lion kt88.. but more musical imho. I do not feel the need to invest in 150s. 

I have a Primaluna Dialogue Premium HP amp and have used EL34’s, 7581’s, and last week installed KT150’s. I have not tried the KT120. I totally agree with everyone’s comments about the 7581. Fantastic tube for 30 bucks. Deeper and tighter than the EL34 which I don’t use much anymore even though they have a wonderfully liquid midrange.

I’m only one week in with the KT150s but they do everything that the 7581’s do well but better, particularly soundstaging and depth. I wasn’t at all expecting those changes to the degree I have experienced. Imaging is better too. Everything I have read about the KT150 talks about the fullness, bass depth, tightness, which I agree with, but I was surprised with the rendition of space.

Again, I only have 25 hours or so of actual listening time on the KT150’s so we’ll see what they do over a longer period of time and the honeymoon period has worn off. I’ll wrap up by saying this though, if you are a bit hesitant to slap down 100 bucks per KT150, the 7581 is a fantastic alternative, kind of a KT150 lite. But I really do like the KT150s (all $800 worth, yikes!) 

For what it’s worth...

Comparing, re-tubing an older KT88 based amp that will "accept" KT150s vs. an amp which was designed day-1 (with larger transformers, and higher plate voltages) to natively run KT150s optimally, "can" "sometimes" yield a different listening experience. I’ve run across this with 3 different amps.

While I really enjoy the KT150s in my current mono block amps, they were originally designed to run them. Sounds great. However, a good friend just removed KT150s from his older amp, and he went back to KT88s as his amp was originally designed for them. In his case, I too preferred the KT88s in his amp. His upgrade to KT150s was a waste in his particular situation. Found out later his amp had much lower plate voltages, and (apparently) was not able to fully drive and take advantage of the more expensive TS KT150s.

It seems the amp/design/circuit has something to do with it as well. Probably worth checking with the amp designer to see if it’s worth it. A case of bigger or newer may not always be better.